Symposium Organizers
Nian Sun, Northeastern University
Franz Faupel, Kiel University
Cewen Nan, Tsinghua University
Ramamoorthy Ramesh, University of California, Berkeley
EM02.01: Magnetoelectrics I
Session Chairs
Long-Qing Chen
Eckhard Quandt
Monday PM, November 27, 2017
Hynes, Level 1, Room 107
8:00 AM - EM02.01.01
New Vertical Aligned Nanocomposite Films with Strong Room Temperature Converse Magnetoelectric Effect
Rui Wu 1 , Seungho Cho 1 , Ahmed Kursumovic 1 , Judith MacManus-Driscoll 1
1 Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, Cambridgeshire, United Kingdom
Show AbstractVertically aligned nanocomposites (VANs) with the 3-1 structure, containing ferroelectric and ferro/ferrimagnetic materials, have the possibility to achieve magnetoelectric coupling for ultra-high density magnetic recording with low-power electric-writing via voltage driven magnetization switching. So far, the BaTiO3-CoFe2O4 (BTO-CFO) and BiFeO3- CoFe2O4 (BFO-CFO) VANs have been intensively studied. However, the relatively low Curie temperature of BTO (Tc of 393 K) and large leakage in the BFO limits device applications. Therefore, new materials and precise nanoengineering of these new materials is required. In this work, we have explored alternative high Tc ferroelectrics and CFO in a new VAN system. The leakage problem is overcome by exploiting several new features in the system. Both excellent ferroelectric properties and ferrimagnetic properties are achieved. Strong converse magnetoelectric coupling is achieved in this system, enabling the control of magnetism with in-situ electric field at room temperature.
8:15 AM - EM02.01.02
Limited Polarization Reversal in Ferroelectric/Ferrimagnetic κ-Al2O3-type Structured Materials
Shintaro Yasui 1 , Tsukasa Katayama 1 , Yosuke Hamasaki 1 , Ayako Konishi 2 , Hiroki Moriwake 2 , Takahisa Shiraishi 3 , Akihiro Akama 3 , Takanori Kiguchi 3 , Mitsuru Itoh 1
1 , Tokyo Institute of Technology, Yokohama Japan, 2 , Japan Fine Ceramics Center, Nagoya Japan, 3 , Tohoku University, Sendai Japan
Show AbstractPerovskite type structured ferroelectric materials such as BaTiO3 and Pb(Zr,Ti)O3 and related compounds have been used for memory, sensor and various applications since they are found around 70 years ago. Whether good or bad, since Perovskite-type ferroelectrics are found, they have been used because of their superior ferroelectric and piezoelectric properties. To overcome this situation, we would like to suggest novel ferroelectric/ferrimagnetic ferroelectric which has κ-Al2O3 type crystal structure classified as polar Pna21 space group. However, almost all of the materials with k-Al2O3 type crystal structure are metastable phase, which is difficult to stabilize at ambient pressure. Here, we succeeded to prepare this structure’s materials. For example, ScFeO3 epitaxial thin films having κ-Al2O3 type crystal structure were prepared on (111)SrTiO3 single crystal substrates by pulsed laser deposition. Growth of metastable ScFeO3 phase was controlled by film preparation technique. Polarization-electric field loops were measured at room temperature using Pt/ ScFeO3/SrRuO3 capacitor structure. Saturation polarization of 5 μC/cm2 was observed at 100 Hz. We also carried out first principle calculation for investigation of switching mechanism in κ-Al2O3 type structure. Novel polarization switching way was considered through paraelectric phase with lower activation energy of 0.1-0.15 eV than that with reported value of 0.5 eV at Pnna phase. This result suggests that polarization switching should be occurred by electric field. However, observed polarization was smaller than calculated value of 20 μC/cm2. To investigate this phenomenon, (S)TEM observation was carried out. As a result, very small domains having 5-15 nm2 area existed in the films and they were grown on the substrate with columnar structure. From the first principal calculation, polarization switching was occurred by zig-zag shear moving of oxygen layer along a-axis. Unfortunately, polarization switching should not be occurred due to limitation of oxygen moving by domain formation. However, there were some anti-phase boundary and defects in the large domain, which could assist polarization switching owing to create a space of oxygen moving. As a result, smaller polarization value was obtained. Ferrimagnetic and multiferroic properties in this materials will be discussed, also.
8:30 AM - *EM02.01.03
Magnetoelectric Magnetic Field Sensors
Eckhard Quandt 1
1 , University of Kiel, Kiel Germany
Show AbstractMagnetoelectric (ME) composite materials show ME coefficients that are larger than that of natural multiferroics by several orders of magnitude. These ME composites have high potential for applications, e.g. as very sensitive ac magnetic field sensors. Special features are their passive nature, their high sensitivity, and their large dynamic range with linear response. By a suitable combination of magnetic shape anisotropy and field annealing it is possible to obtain a sensor element that has a pronounced sensitivity in only one dimension being a component of a 3-dimensional vector field sensor, which is highly desirable for applications like magnetoencephalography (MEG) or –cardiography (MCG).
The thin film ME components are AlN (1) or ferroelectric piezoelectrics (e.g. PZT) and different magnetostrictive single and multi layers. Upon magnetic field annealing these ME composites show an uniaxial magnetic anisotropy (2) and an extremely high ME coefficient of approximately to 5 kV/cmOe at mechanical resonance and a limit of detection below 500 fT/Hz1/2 (3).
In this presentation different thin film composites will be discussed in terms of their use as very sensitive magnetic field sensors in the pT range at biomagnetic relevant frequencies (1-100 Hz). To obtain sufficient limit of detections (LODs) in the required low frequency range magnetic (4) and electric (5) modulation techniques are investigated. As an alternative to modulated sensors, sensors based on the DE-effect using either ME cantilever-type sensors (6) or surface acoustic wave (SAW) sensors will be presented.
Funding by the DFG via the Collaborative Research Center SFB 1261 is gratefully acknowledged.
(1) Yarar, E.; Hrkac, V.; Zamponi, C.; Piorra, A.; Kienle, L.; Quandt, E.: Low temperature aluminum nitride thin films for sensory applications, AIP Advances 6 (2016), 075115.
(2) Greve, H.; Woltermann, E.; Quenzer, H.J.; Wagner, B. and Quandt, E.: Giant Magnetoelectric Coefficients in (Fe90Co10)78Si12B10-AIN Thin Film Composites, Appl. Phys. Lett. 96 (2010), 182501.
(3) Yarar, E.; Salzer, S.; Hrkac, V.; Piorra, A.; Höft, M.; Knöchel, R.; Kienle, L.; Quandt, E.: Inverse bilayer magnetoelectric thin film sensor, Appl. Phys. Lett. 109 (2016), 022901.
(4) Jahns, R.; Greve H.; Woltermann, E.; Quandt, E.; Knöchel, R.: Sensitivity enhancement of magnetoelectric sensors through frequency-conversion, Sensors and Actuators A: Physical, 183 (2012), 16-21.
(5) Hayes, P.; Salzer, S.; Reermann, J.; Yarar, E.; Röbisch, V.; Piorra, A.; Meyners, D.; Höft, M.; Knöchel, R.; Schmidt, G.; Quandt, E.: Electrically modulated magnetoelectric sensors, Appl. Phys. Lett. 108 (2016), 182902.
(6) Zabel, S.; Kirchhof, C.; Yarar, E.; Meyners, D.; Quandt, E; F. Faupel: Phase modulated magnetoelectric delta-E effect sensor for subnano tesla magnetic fields, Appl. Phys. Lett. 107 (2015),152402.
9:00 AM - EM02.01.04
Acoustically Actuated Ultra-Compact NEMS Magnetoelectric Antennas
Hwaider Lin 1 , Tianxiang Nan 1 , Nian Sun 1
1 , Northeastern University, Boston, Massachusetts, United States
Show AbstractState-of-the-art compact antennas rely on electromagnetic wave resonance, which leads to antenna sizes that are comparable to the electromagnetic wavelength λ. As a result, antennas typically have a size of >λ /10, and the antenna miniaturization has been an open challenge for decades. Here we report on acoustically actuated nanomechanical magnetoelectric (ME) antennas with a suspended ferromagnetic (FeGaB)/ piezoelectric (AlN) thin film heterostructure. These ME antennas receive and transmit electromagnetic waves through a strong ME coupling effect at their acoustic resonance frequencies. The piezoelectric-induced acoustic resonance in ME antennas stimulates magnetization dynamics in FeGaB thin film through a ME coupling, which results in magnetic currents and radiation of electromagnetic waves. Vice versa, these antennas sense the magnetic fields of electromagnetic waves, giving a piezoelectric voltage output. The ME antennas (with sizes of λ /1000 ~ λ /100) demonstrates 1~2 orders of magnitude miniaturization over state-of-the-art compact antennas without performance degradation. Our experimental results are confirmed by finite element simulations. These acoustically actuated ultra-miniaturized ME antennas have potential implications for internet of things (IoT), and portable wireless communication systems.
Reference: 1. T. Nan, et al. Scientific Reports, 2. T. Nan, et al. Nature Comm. in press.
9:15 AM - *EM02.01.05
Strain Mediated Multiferroic for Efficiently Controlling Nanoscale Magnetism
Gregory Carman 1
1 , University of California, Los Angeles, Los Angeles, California, United States
Show AbstractThis presentation reviews the progress we have made on modeling, fabrication and testing of nanoscale heterogeneous structures fabricated with piezoelectric and magnetostrictive materials. The modeling consists of solving the dynamic coupled partial differential equations represented by micromagnetics and elastodynamics using a finite element based model. These numerical codes are used to design and understand dynamic testing of Ni, CoFeB, and TbDyFe magnetostrictive single domain elements. Experimental data on nanodots, rings, and spin bus elements are presented.
One of the primary problems facing the strain mediated multiferroic approach is substrate clamping. In this presentation we use a model along with experimental data to show that thin film piezoelectrics with island electrodes approach the strain of bulk pieoelectrics. For the magnetic single domain nanodots, perpendicular magnetic anisotropy PMA is produced during fabrication by either interface interactions (CoFeB/MgO) or residual stresses (TbDyFe). For both of PMA materials, the magnetic orientation can be rotated 180 degree using precessional switching in realisitc structues with energy costs on the order of 20 aJ. The dynamic response is limited by ferromagnetic resonance values with switching times on the order of ~ns. For nanoring structures with magnetic onion states, the structure can be rotated 360 degrees with as few as one pair of electrodes if other anisotropies are designed into the system such as magnetocrystalline anisotropy. Here, the selection of the shape, orientation and electrode placement is key to rotating structures and prevent loss of the onion state. Finally, spin wave buses can be excited using acoustic waves at frequency substantially lower than FMR for much larger distances than pure-spinwave. This approach to transmitting magnetic information has been termed spin wave surfing due to the spin wave propogation and regeneration by the underlying acoustic wave. In general, these results demonstrate a substantially more efficient approach to controlling magnetism than presently avaiable. However, ancillary issues still pose problems for implementations such as defects, surface roughness, and non-uniform strain.
9:45 AM - EM02.01.06
Modelling the Delta-E Effect for Sensor Applications
Benjamin Spetzler 1 , Sebastian Zabel 1 , Anne Kittmann 2 , Jeffrey McCord 3 , Eckhard Quandt 2 , Franz Faupel 1
1 Institute for Materials Science, Chair for Multicomponent Materials, University of Kiel, Kiel Germany, 2 Institute for Materials Science, Chair for Inorganic Functional Materials, University of Kiel, Kiel Germany, 3 Institute for Materials Science, Chair for Nanoscale Magnetic Materials, University of Kiel, Kiel Germany
Show AbstractThe ΔE effect of magnetoelastic materials recently proved exciting potential for magnetic field sensors. We discuss the effect in general and its application in diverse types of electrically excited sensors including the most common like cantilevers or bulk resonators. Magnetic and mechanical simulations are tested against experimental data including MOKE imaging. The tensorial simulation allows for arbitrary sets of magnetic configuration and type of sensor deformation. This enables e.g. to study changes in the shear modulus which offers greater sensitivity in sensor applications. As another important aspect for the sensor performance, magnetoelastic damping is considered. Also, the magnetic domain configuration is of interest because domain effects are a major internal noise source. The detailed understanding of the magnetoelastic processes allows for adapted sensor design with very competetitive performance
10:30 AM - *EM02.01.07
Understanding Domain Structures and Topological Defects in Multiferroic Improper Ferroelectrics Using Phase-Field Simulations
Fei Xue 1 , Xueyun Wang 2 , Sang Wook Cheong 2 , Long-Qing Chen 1
1 , The Pennsylvania State University, University Park, Pennsylvania, United States, 2 , Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States
Show AbstractPolarization in improper ferroelectrics is induced by other structural deformations and thus a secondary order parameter. Hexagonal manganites h-REMnO3 (RE, rare earths) are one important type of multiferroic improper ferroelectrics displaying intriguing physics and potential applications. The six domain variants in h-REMnO3 form vortex and antivortex cores, or generally called “topological defects”. The temporal and spatial evolution of the vortex domain structures can be obtained using phase-field simulations, which allows us to fully explore the mesoscale mechanisms for the vortex-antivortex annihilation, evolution of vortex loops, and domain wall motion with and without external electric fields. It is demonstrated that the vortex motion and vortex-antivortex annihilation control the kinetics of domain structure evolution. It is discovered that the vortex loops may undergo three types of topological transformations, i.e., shrinking, coalescence, and splitting. Furthermore, it is shown that an in-plane strain can unfold the vortices into single-chirality striped domains. The dependences of the stabilities of the vortex domains and striped domains on temperature and strain will be discussed.
11:00 AM - EM02.01.08
Magnetostrictive FeGaB Layers on Si and Quartz Substrates for Magnetoelectric and SAW Sensor Applications
Rahel Kruppe 1 , Anne Kittmann 1 , Dirk Meyners 1 , Eckhard Quandt 1
1 , Institute for Material Science, Kiel University, Kiel Germany
Show AbstractTo be able to measure weak, low frequency magnetic signals it is possible to use thin film composite magnetoelectric (ME) or surface acoustic wave (SAW) sensors, which are comprised of a piezoelectric and a magnetostrictive phase. Among considering the piezoelectric phase and sensor design issues, it is necessary to tune the magnetostrictive phase regarding its pseudo-piezomagnetic coefficient dλ/dH and its inherent noise. In the last few years it was shown that very good results concerning the magnetoelectric coefficient αME of mechanically resonant ME sensors could be achieved using e. g. FeCoSiB as magnetostrictive material as a single layer [1] as well as exchange biased multilayers [1–3]. To further optimize the sensor responses, FeGaB as a highly magnetostrictive, soft magnetic material with low anisotropy field is very interesting for ME sensors as well as SAW sensor applications. As a thin film, its magnetic properties are tied strongly to the film morphology and the substrate/film interface, thus necessitating the investigation of the morphological and interfacial effects.
Within the scope of this work, FeGaB is to be used as the magnetostrictive phase in a mechanically resonant ME sensor with a Si substrate and a SAW sensor with a Quartz substrate. Thus, we investigate the RF-magnetron sputter deposition of thin films from single targets with a narrow range of compositions of (Fe80Ga20)1-xBx (x=10, 12 and 14) on Si and quartz substrates. The focus of the investigations lies on the effect of the substrates, the deposition conditions, e.g. substrate temperature, in-field deposition, and post deposition treatments on the magnetic and morphological properties of the thin films.
Funding by the DFG (SFB 1261) and ERDF (Competence Center Nanosystem Technology) is gratefully acknowledged.
References
1. Jahns, R.; Piorra, A.; Lage, E.; Kirchhof, C.; Meyners, D.; Gugat, J. L.; Krantz, M.; Gerken, M.; Knöchel, R.; Quandt, E. Giant magnetoelectric effect in thin-film composites. J. Am. Ceram. Soc. 2013, 96, 1673–1681.
2. Lage, E.; Kirchhof, C.; Hrkac, V.; Kienle, L.; Jahns, R.; Knöchel, R.; Quandt, E.; Meyners, D. Exchange biasing of magnetoelectric composites. Nat. Mater. 2012, 11, 523–529.
3. Durdaut, P.; Salzer, S.; Member, S.; Reermann, J.; Member, S.; Hayes, P.; Meyners, D.; Quandt, E.; Schmidt, G.; Knöchel, R.; Michael, H. Thermal-Mechanical Noise in Resonant Thin-Film Magnetoelectric Sensors. IEEE Sens. J. 2017, XX, 1–11.
11:15 AM - EM02.01.09
Exchange Biased Magnetostrictors for Magnetic Frequency Conversion
Dirk Meyners 1 , Volker Röbisch 1 , Matic Klug 1 , Sebastian Salzer 1 , Phillip Durdaut 1 , Michael Höft 1 , Eckhard Quandt 1 , Jeffrey McCord 1
1 , Kiel University, Kiel Germany
Show AbstractComposite magnetoelectric (ME) materials have proven to exhibit strong magnetoelectric coupling, because they benefit from the advantage that their constituting phases can be optimized almost independently. Consequently, highly sensitive magnetic field sensors could be demonstrated, showing a low limit of detection in the picotesla range for bulk and thin film magnetoelectric heterostructures [1, 2]. The highest sensitivity is reached when signal enhancement by mechanical resonance is utilized. As a drawback of this approach, the ME sensor bandwidth is limited by the mechanical resonance. Frequency conversion techniques have been proposed to shift the frequency range with high sensitivity to the desired frequency band [3]. For this purpose, in case of magnetic frequency conversion, a strong modulating magnetic field is applied. As a result, the magnetization of the ME composite changes periodically, potentially giving rise to an additional noise source due to magnetic domain activity.
This presentation considers thin film heterostructures fabricated by bulk micromachining using Si substrates. The thin film approach to ME composites enables stacking of complex layer structures with tuned properties. As the piezoelectric phase, 2 µm thick AlN is grown by pulsed DC sputtering on a Pt seed layer. Single and complex exchanged biased multilayers consisting of (Fe90Co10)78Si12B10 form the magnetostrictive phase. The multilayers are based on the stacking order unit Ta 5 / Cu 3 / MnIr 8 / FeCoSiB x [thickness in nm] with varying thickness x of the FeCoSiB layer. The total thickness of the FeCoSiB layers is adjusted to 1 µm, 2 µm and 4 µm, respectively. Applying a multistep thermal treatment, antiparallel alignment of magnetizations in adjacent ferromagnetic layers is achieved in order to eliminate magnetic domain formation in magnetic layers. Patterning of functional layers and electrodes is done by a combination of dry and wet chemical etching. Finally, the samples are diced into cantilever structures with typical lateral dimensions of 2.2 mm x 25.2 mm.
The ME cantilever sensors with varying magnetostrictive multilayers are compared in regard to ME voltage coefficient, noise voltage density and minimum detectable field. It is demonstrated that during frequency conversion the concept based on stray magnetic field reduction yields a significant reduction in noise by more than one order of magnitude.
[1] Wang, Y.; Gray, D.; Berry, D.; Gao, J.; Li, M.; Li, J.; Viehland, D. (2011), Advanced materials 23 (35), 4111–4114.
[2] Yarar, E.; Salzer, S.; Hrkac, V.; Piorra, A.; Höft, M.; Knöchel, R. et al. (2016), Appl. Phys. Lett. 109 (2), 22901.
[3] Jahns, R.; Greve, H.; Woltermann, E.; Quandt, E.; Knöchel, R. (2012), Sensors and Actuators A: Physical 183, 16–21.
11:30 AM - *EM02.01.10
Control of Magnetism in Heterostructural Composites Using Large Phase Transformational Strain
Peter Finkel 1 , Margo Staruch 1
1 , U.S. Naval Research Laboratory, Washington, District of Columbia, United States
Show AbstractThe ability to tune both magnetic and electric properties concomitantly in magnetoelectric (ME) composite heterostructures, consisting of magnetostrictive and piezoelectric phases coupled through strain, makes them very promising in many applications and devices due to additional functionalities attributed to ME interactions between two phases [1,2]. In this talk we demonstrate different approaches to achieve maximum ME coupling in heterostructures of magnetostrictive films deposited on domain-engineered relaxor ferroelectric single crystals. Much work has been done over the past decade to maximize the magnetoelectric (ME) coupling coefficient, aME, the figure of merit for these composites. The ME coupling coefficient can be enhanced through deliberate choice of materials as well as carefully controlling the interface. For the piezoelectric phase, relaxor ferroelectrics have attracted much attention recently due to a piezoelectric coefficient an order of magnitude larger than conventional lead zirconate-titanate. There has recently been much interest in single crystal Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) due to its high piezoelectric coefficient with larger linear range and temperature stability than binary relaxors. Further, domain-engineered (011) oriented crystals also demonstrate a stress, electric field, or temperature induced rhombohedral to orthorhombic transition which results in a sharp change in strain (up to 0.5%) at remarkably low fields (0.1 MV/m) when biased with a compressive mechanical stress [3]. It would be of great interest to utilize the remarkable piezoelectric properties of PIN-PMN-PT in ME composites to control magnetization. Previously we demonstrated one of the largest value of the converse magnetoelectric coupling coefficient (aCME) of ~ 4 x 10-6 s/m achieved for a FeCo/Ag multilayered film on PIN-PMN-PT in the linear piezoelectric regime, thus representing a step towards practical ME transduction devices [4]. By exploiting the large transitional strain that occurs at very low fields when brought to a critical point by temperature or stress, the converse magnetoelectric coupling (CME) coefficient aCME = m0dM/dE change in magnetization with electric field is expected to be greatly enhanced as compared to linear piezoelectricity. In this presentation, the impact of this enhancement will be examined and a path for utilization of this phenomenon will be discussed.
1. Hu, J.-M., Li, Z., Chen, L.-Q. & Nan, C.-W, Nat. Commun. 2, 553 (2011).
2. R. Ramesh & N.A. Spaldin, Nat. Mater. 6, 21–29 (2007).
3. P. Finkel et al., Scientific Reports, published online Sept 08, 2015, DOI:10.038/srep13770.
4. M. Staruch et al., Scientific Reports http://www.nature.com/articles/srep37429
EM02.02: Multiferroics I
Session Chairs
Sang Wook Cheong
Chang-Beom Eom
Monday PM, November 27, 2017
Hynes, Level 1, Room 107
1:30 PM - *EM02.02.01
Hybrid Improper Ferroelectricity
Sang Wook Cheong 1
1 , Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States
Show AbstractHybrid improper ferroelectricity (HIF), which describes a state with the polarization induced by a hybridization of two non-polar lattice instabilities, holds great promise toward the realization of room-temperature multiferroelectricity. The key idea is to design new materials in which ferroelectricity and (anti)ferromagnetism can be coupled by the same lattice instability, therefore providing an indirect but strong coupling between polarization and magnetism. Exemplary compounds with HIF include the double-layered Ruddlesden-Popper (RP) perovskites with the chemical formula of A3B2O7 (A2+ = alkali metal; B4+ = transition metal), PbTiO3/SrTiO3 superlattice and AA’B2O6 double perovskites. In addition, the presence of related polar space groups has been reported in Dion-Jacobson compounds ABiNb2O7 (A = Rb, Cs), RP-phase ferrite composites and Ca3Mn2O7.
We have, for the first time, grown single crystals of (Ca,Sr)3Ti2O7, and experimentally confirmed the existence of hybrid improper ferroelectricity in the crystal. Furthermore, we found that charged ferroelectric domain walls (FE DWs), some of which are highly conducting, are mysteriously abundant in the recently discovered (Ca,Sr)3Ti2O7 crystals. Head-to-head and tail-to-tail 180o FE DWs exhibit an approximately 100 times conduction difference in the conductive atomic force microscopy (c-AFM) measurements. We also discover a zipper-like nature of domain walls with high energy; they are the reversible creation/annihilation centers of ferroelectric wall pairs for the process of 90o and 180o polarization switching. Note that we have also prepared high-quality Sr3Sn2O7 specimens, and experimentally proved the presence of HIF in Sr3Sn2O7.
RP-phase Ca3Mn2O7 has been proposed as a prototypical HIF magnet. In addition, a relative large, possibly questionable, magnetoelectric (ME) effect (72 ps/m) has been reported in polycrystalline Ca3Mn2O7 at 4 K. However, no measurable FE polarization has been reported in Ca3Mn2O7. We have, for the first time, grown single crystals of Ca3Mn2O7 and confirmed the presence of polar domains in Ca3Mn2O7. However, we discovered that our Ca3Mn2O7 crystals exhibit highly-irregular orthorhombic twin structures, distinct from the prototypical straight twin structure. We also found that the polarization of Ca3Mn2O7 is non-switchable in the electric field range that we can apply. We will discuss the origin of the unprecedented twin structure in Ca3Mn2O7, and also its interrelationship with non-switchability of polarization. Our results on a number of HIF materials pave a new avenue to design new ferroelectrics with enhanced functionalities and also novel multiferroics with room-temperature magnetoelectricty.
2:00 PM - EM02.02.02
Multiferroicity in Ordered Ferrites
Antoine Maignan 1 , Christine Martin 1
1 , CRISMAT, CNRS and ENSICAEN, Caen Cedex France
Show AbstractThe Fe based oxides form a large family of magnetic compounds, in which the Fe2+:Fe3+ oxidations states favor a low electrical conductivity as illustrated by the SrFe12O19 hexaferrites. The ferrites showing cationic ordering are good candidates for multiferroicity: for instance, charge ordering at the metal sites can be responsible for charges off centering [1] as well as structures in which metallic cations exhibit preferential occupations as in YBaFeCuO5 [2]. In the latter, a triple ordered perovskite, the Y and Ba are ordered in the perovskite cages of the perovskite, and oxygen are also ordered in a way that ribbons of double square planar pyramids are created where the Cu and Fe cations order. This antiferromagnetic oxide is a multiferroic with a magnetoelectric coupling near room temperature [3].
Searching for charge ordered ferrites, the Fe oxyborates appeared to be attractive candidates. In the Fe3BO5 vonsenite, the Fe2+ and Fe3+ cations order on different crystallographic sites (TCO=283K) leading to complex antiferromagnetic structures below TN1=112 K and TN2=70 K [4].
In the T region of TN, a magnetodielectric coupling is evidenced (maximum near TN2) [5]. The pyroelectric measurements performed in different bias electrical fields show the existence of an intrinsic electrical polarization near 65K, confirming the ferroelectricity. The site selective substitution of Mn2+ for Fe in this compound is found to make the polarization increases [5].
These results will illustrate the potentialities of cation order in ferrites to generate multiferroic materials.
[1] D.I. Khomskii, J. Magn. Magn. Mater., 306 (2006) 1.
[2] M. Morin et al., Phys. Rev. B, 91 (2015) 064408.
[3] B. Kundys et al., Appl. Phys. Lett., 94 (2009) 072506.
[4] P. Bordet et al., Phys. Rev. B, 79 (2009) 144408.
[5] A. Maignan et al., J. of Solid State Chem., 246 (2017) 209.
2:15 PM - *EM02.02.03
Spin Texture of Ferroelectric HfO2
Evgeny Tsymbal 1 , Lingling Tao 1 , Tula Paudel 1 , Alexey Kovalev 1
1 Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, Nebraska, United States
Show AbstractSpin-orbit coupling is known to be responsible for non-trivial spin configurations and a number of emergent physical phenomena. Ferroelectric materials are especially interesting in this regard due to their non-centrosymmetric atomic structure and reversible spontaneous polarization, which allows for a non-volatile electrical control of the spin degrees of freedom. Here, we explore a technologically relevant oxide material, HfO2, exhibiting robust ferroelectricity in a non-centrosymmetric orthorhombic phase. Using theoretical modeling based on density-functional theory, we investigate the spin-dependent electronic structure of the ferroelectric HfO2 and demonstrate the appearance of chiral spin textures driven by spin-orbit coupling. We develop an appropriate model to analyze these spin configurations and find that the Rashba-type spin texture dominates around the valence band maximum, while the Dresselhaus-type spin texture prevails around the conduction band minimum. The latter is characterized by a very large Dresselhaus constant, which allows using this material as a tunnel barrier to produce tunneling anomalous and spin Hall effects that are reversible by ferroelectric polarization.
2:45 PM - EM02.02.04
Enhanced Curie Temperature of In-Plane Ferroelectric Epitaxial BaTiO3 Thin Films for Multiferroic Heterostructures
Katsuyoshi Komatsu 1 , Ippei Suzuki 1 , Takumi Aoki 2 , Yosuke Hamasaki 1 , Shintaro Yasui 1 , Mitsuru Itoh 1 , Tomoyasu Taniyama 1
1 Laboratory for Materials and Structures, Tokyo Institute of Technology, Yokohama, Kanagawa, Japan, 2 Advanced Technology Development Center, TDK Corporation, Ichikawa, Chiba, Japan
Show AbstractRecently, ferromagnetic/ferroelectric heterostructures have been actively studied for electric control of magnetization. Our previous experiments have demonstrated pure electric field induced switching of perpendicular magnetization in [Cu/Ni] multilayer/BaTiO3 (BTO) [1]. However, a large voltage over 100 V is required to induce the magnetization switching with such bulk substrates. In order to reduce the required voltage, the use of a thin ferroelectric underlayer is an appropriate solution. Thin film ferroelectrics, however, are widely recognized to possess out-of-plane polarization due to interface effects, making it difficult to control the magnetization orientation by switching the polarization from in-plane to out-of-plane. In this work, we demonstrate a well-defined in-plane ferroelectric polarization in BTO thin films on MgAlO4(001) (MAO) as well as the enhanced Curie temperature, which is firstly observed for BTO thin films with tensile strain.
BTO thin films were grown on MAO substrates, that induce a positive epitaxial misfit strain ~0.9% in BTO thin films, using pulsed laser deposition. X-ray reciprocal lattice mapping shows clear epitaxial growth of BTO film while no splitting arising from a1 and a2 in-plane domains is seen due to the broadening of the diffraction peaks. In order to confirm the in-plane polarization, we measure the polarization-electric field (P-E) curves of the epitaxial BTO films using a pair of capacitor type top electrodes defined by electron beam lithography. The P-E curves clearly show hysteretic behavior with a saturation polarization of 22.3 mC/cm2. The P-E measurements for different field directions show that P//[110] is 10% larger than P//[100], indicating that the BTO film has an orthorhombic crystal structure rather than a tetragonal one. This is consistent with the recent theoretical prediction [2]. The full width at half maximum of the in-plane diffraction peak is found to decrease with increasing temperature and shows a plateau above 220°C, in contrast to the fact that the temperature dependence of in-plane and out-of-plane lattice constants increases monotonically up to 700°C. This indicates that the BTO films undergo the orthorhombic to cubic phase transition at 220°C and the splitting of the orthorhombic ferroelectric domains disappears above this temperature as expected by theoretical calculations [2]. From these results, we conclude that the ferroelectric Curie temperature of BTO thin films with in-plane tensile strain is 100°C higher than that of bulk BTO, which has a great advantage, with a view to fabricating multiferroic thin film heterostructures with perpendicular magnetic anisotropy that can be switched to in-plane anisotropy by a rather low electric voltage.
[1] Y. Shirahata, R. Shiina, D. L. Gonzalez, K. J. A. Franke, E. Wada, M. Itoh, N. A. Pertsev, S. van Dijken, and T. Taniyama, NPG Asia Mater. 7, e198 (2015).
[2] Y. L. Li and L. Q. Chen, Appl. Phys. Lett. 88, (2006).
3:30 PM - *EM02.02.05
Voltage-Controlled Switching of Boundary Magnetization—A Fundamental Phenomenon with Potential Application in Ultra-Low Power Spintronics
Christian Binek 1 , Will Echtenkamp 1 , Mike Street 1 , Ather Mahmood 1 , Peter Dowben 1 , Junlei Wang 1
1 , Univ of Nebraska-Lincoln, Lincoln, Nebraska, United States
Show AbstractVoltage-controlled magnetization switching at surfaces, interfaces or boundaries in layered heterostructures enables dissipationless control of remnant magnetic states. It paves the way towards scalable, ultra-low power, and non-volatile spintronics. We exploit electrically switchable boundary magnetization (BM) of the magnetoelectric (ME) antiferromagnet chromia and its Boron doped high-TN counterpart. Quantum mechanical exchange at the interface between a ferromagnetic (FM) CoPd thin film of perpendicular anisotropy and BM at the (0001) surface of chromia enables voltage-controlled exchange bias (VCEB), i.e., electrically shifting of the FM hysteresis along the magnetic field axis [1,2,3]. Similarly, we investigate VC switching of induced magnetization in nonmagnetic metals (NM) with high Stoner susceptibility [4]. Polar Kerr and anomalous Hall effect are employed to measure magnetization induced by the exchange field of the BM exerted on NMs. VC switching of induced magnetization can overcome problems associated with the energy-delay constraints accompanying reversal of magnetization in ferromagnets [5]. In both chromia/FM and chromia/NM hetero-layers, different forms of switchable magnetization serve as non-volatile state variable enabling ultra-low power memory and logic devices. I report on the challenging realization of VCEB in all thin film geometry and the role of BM as a key element to overcome limitations due to the weak linear ME susceptibility of bulk chromia. I introduce voltage-switchable BM and VCEB, provide experimental evidence, and present our latest results on VCEB and VCBM in patterned thin films with reference to applications. In addition, I introduce a tabletop magneto-optical method to measure electric field induced Faraday rotation in ME antiferromagnets, switching of the antiferromagnetic order parameter and the accompanying BM [6].
We acknowledge support by NERC, a wholly-owned subsidiary of SRC, through CNFD, an SRC-NRI Center under Task IDs 2398.001 and 2587.001, by C-SPIN, one of six centers of STARnet, a SRC program, sponsored by MARCO and DARPA, and by NSF through MRSEC DMR-1420645. Research was performed in part in the NNF supported by the NSF under Award NNCI: 1542182.
1. Xi He, et al., Nature Mater. 9, 579 (2010).
2. W. Echtenkmap, Ch. Binek, Phys. Rev. Lett. 111, 187204 (2013).
3. W.Echtenkamp, M. Street, A. Mahmood, Ch. Binek, Phys. Rev. Appl. (2017).
4. S. Cao et al., J. Phys.: Condens. Matter 29, 10LT01 (2017).
5. T. Kosub et al., Nature Commun. 8, 13985 (2017).
6. J. Wang, Ch. Binek, Phys. Rev. Applied (letter) 5, 031001 (2016)
4:00 PM - EM02.02.06
Polarization Switching in Ferroelectrics and Multiferroics by a Single-Period Terahertz Pulse
Elena Mishina 1 , Kirill Grishunin 1 , Vladislav Bilyk 1 , Mikhail Agranat 2 , Alexeq Kimel 1 3
1 , Moscow Technological University (MIREA), Moscow Russian Federation, 2 , Joint Institute for High Temperature of Russian Academy of Sciences, Moscow Russian Federation, 3 Institute for Molecules and Materials, Radboud University Nijmegen, Nijmegen Netherlands
Show AbstractThe search for ways to control theorder parameter (magnetization or polarization) of a medium with the maximum possible speed is important both from the point of view of fundamental physics and for technology of memory elements operating at frequencies from tens of gigahertz to terahertz. The greatest potential from the point of view of speed is possessed by controlling the order parameter by ultrashort electromagnetic pulses.
Recently experiments revealed that magnetization can be switched in magnetic metals using circularly polarized femtosecond optical pulse [1] and in transparent magnetic materials using linearly polarized femtosecond optical pulse [2]. Sub-cycle THz pulses were also proposed for switching of order parameter. A mechanism for spin reorientation by strong electric component of sub-cycle THz pulse was proposed [3]. In ferroelectrics, dynamical switching of polarization by THz pulse was shown [4].
In this paper, we present the results of experimental and theoretical study of the dynamic switching of polarization in ferroelectrics and multiferroics, as well as the creation of quasi-remnant polarization (within and after action of THz field, respectively). Materials under the study were: epitaxial ferroelectric (BaSr)TiO3 film and multiferroic (BaSr)TiO3/BiFeO3 multilayer.
Sub-cycle terahertz field up to 1 MV/cm was generated by optical rectification in an organic crystal with the help of femtosecond optical pulse. As a measure of the dielectric polarization, the intensity of second harmonic generation (SHG) was recorded as a function of a delay time between THz pump and femtosecond optical probe. SHG parameters were used as measure of the order parameter (magnetization or dielectric polarization). Optical polarization characteristics allow us to distinguish between different contributions to SHG intensity.
Experiments revealed that under the action of THz pulse on the samples, two effects were observed: modulation of the SHG intensity with exactly the shape of THz pulse and a step-like change of the SHG intensity overlapped by oscillating signal after the THz pulse ended. The former reveals transient modulation of polarization within the THz pulse duration, the latter we assign to switching of the polarization and creation of remnant polarization. Both effects took place due to displacements of ions, which were earlier observed in experiments on synchronous X-ray structural analysis. The observed switching behavior can be described by nonlinear Duffing equation.
[1] C.D. Stanciu, et al, Phys. Rev. Lett. 99, 047601 (2007).
[2] A. Stupakiewicz, K. Szerenos, D. Afanasiev, et al, Nature 542, 71-74 (2017).
[3] S. Baierl, M. Hohenleutner, T. Kampfrath, et al, Nature Photonics 10, 715 (2016).
[4] K.A. Grishunin, N.A. Ilyin, N.E. Sherstyuk, et al, Scientific Reports 7, 687 (2017).
4:15 PM - *EM02.02.07
Deterministic and Robust Room–Temperature Exchange Coupling in Monodomain Multiferroic BiFeO3 Heterostructures
Chang-Beom Eom 1
1 , University of Wisconsin-Madison, Madison, Wisconsin, United States
Show AbstractExploiting multiferroic BiFeO3 thin films in spintronic devices will require deterministic and robust control of both the internal magnetoelectric coupling in BiFeO3 as well as exchange coupling of its antiferromagnetic order to a ferromagnetic overlayer. Previous reports of exchange coupling in thin films have utilized approaches based on multistep ferroelectric switching with multiple ferroelectric domains. Because domain walls can be attributed to fatigue mechanisms, can contain localized charges either intrinsically or via defects, and present technological problems for device reproducibility and scaling, an alternative approach using a monodomain magnetoelectric state with single–step switching is desirable for practical devices using BiFeO3. Here we demonstrate a room temperature, deterministic and robust exchange coupling between monodomain BiFeO3 films and a Co overlayer that is “intrinsic” (i.e. not dependent on domain walls). Direct coupling between antiferromagnetic order in BiFeO3 and the Co magnetization is observed showing a ~90° in–plane rotation of Co magnetization upon single-step switching that is reproducible for hundreds of cycles. This has important consequences for practical, low power non-volatile magnetoelectric devices utilizing BiFeO3.
*This work has been done in collaboration with WW. Saenrang, B. A. Davidson, F. Maccherozzi, J. P. Podkaminer, J. Irwin, R. D. Johnson, J. W. Freeland, J. Íñiguez, J. L. Schad, K. Reierson, J. C. Frederick, C. A. F. Vaz, L. Howald, T.H. Kim, S. Ryu, M. v. Veenendaal, P.G. Radaelli, S. S. Dhesi, M. S. Rzchowski
**This work was supported by Army Research Office under Grant No. W911NF-13-1-0486.
4:45 PM - EM02.02.08
Strategies for Developing High-Efficiency Ferroelectric Photovoltaics by Resolving the Mechanism of Ferroelectric Photovoltaic Effects
Hyeon Han 1 , Hyun Myung Jang 1
1 , Pohang University of Science and Technology (POSTECH), Pohang Korea (the Republic of)
Show AbstractCurrently, ferroelectric photovoltaic devices are being extensively investigated owing to their anomalously high photovoltages, coupled with reversibly switchable polarizations. Ferroelectric photovoltaics (FPVs) belong to metal oxide (MO) photovoltaics that are known to be chemically stable and environmentally safe. In particular, the FPVs function both as photon absorbers and charge separators. Hence, FPVs can be manufactured as a single active-layered structure. A most outstanding feature of FPVs is that the photovoltage can be a few orders of magnitude larger than the band gap of ferroelectrics due to bulk photovoltaic effect. For example, BiFeO3 thin film has shown the photovoltage of ~200 V when the photocurrent direction is perpendicular to the domain wall. Furthermore, FPVs show the reversibly switchable photovoltaic effect by changing the polarization direction with the aid of an electric field.
Several theoretical models were proposed to account for the FPV effect and associated high photovoltage outputs. These include the shift current model for bulk photovoltaic effect, the domain wall theory, the Schottky-junction effect, and the depolarization field model. Until recently, the FPV effect has remained an academic interest rather than having practical applications owing to the very low output photocurrent densities in the order of nA cm−2 ~ μA cm−2. However, the research activity of FPV solar cells is re-spurred by the three recent breakthroughs: (i) achievement of the power conversion efficiency (PCE) of 8.1 % by band-gap tuning of Bi2(Fe,Cr)O6 ferroelectric multilayers (ii) attainment of PCE exceeding the Shockley-Queisser limit in a BaTiO3 single crystal and (iii) observation of pronounced switchable photovoltaic effects in organometal trihalide perovskite devices.
Herein, we present strategies to develop the high efficient ferroelectric photovoltaic devices by resolving the mechanism of ferroelectric photovoltaic effects. We first demonstrate photovoltaic effect of ferroelectric hexagonal ferrite (h-RFO) thin films, which show reasonably large polarization of ~5 μC cm−2 along with narrow band gap of ~2 eV, which means the h-RFOs are promising FPV devices compared to the typical wide band gap ferroelectrics. Moreover, we show the mechanism of switchable photovoltaic responses in addition to the role of polarization magnitudes in the h-RFO thin film photovoltaics. Next, we introduce the enhancement of ferroelectric photovoltaic efficiencies by applying substrate-induced strain. The strain leads to increased polarization in company with enhancement of solar absorption rate in the FPV system. Finally, we further present other factors affecting the ferroelectric photovoltaic efficiencies. The present study demonstrates the feasibility of a new method to design optimal ferroelectric solar cells and other functional-device applications.
EM02.03: Poster Session I: Magnetoelectrics
Session Chairs
Tuesday AM, November 28, 2017
Hynes, Level 1, Hall B
8:00 PM - EM02.03.01
Magnetic Anisotropy Studies in BiFeO3/SrRuO3 and La0.7Ca0.3MnO3/SrRuO3 Heterostructures
Srinivasa Rao Singamaneni 1 2 3 , Sudhakar Nori 3 , Luis Martinez 1 , Dhananjay Kumar 4 , John Prater 2 , Jagdish Narayan 3
1 Department of Physics, University of Texas at El Paso, El Paso, Texas, United States, 2 Materials Science Division, U.S. Army Research Office, Research Triangle Park, North Carolina, United States, 3 Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina, United States, 4 Department of Mechanical Engineering, North Carolina A&T State University, Raleigh, North Carolina, United States
Show AbstractEmergent as well as interesting physical phenomena arise when two materials of distinct physical properties are in close proximity. In our previous reports1,2, we have observed new magnetic properties such as strong enhancement in coercive field when ferroelectric-antiferromagnetic-insulating layer such as BiFeO3 (BFO) is conjoined with hard ferromagnetic-metallic layer such as SrRuO3 (SRO). Also, we have detected similar magnetic properties when a soft ferromagnetic- metallic layer such as La0.7Ca0.3MnO3 (LCMO) is in close proximity with SRO layer. These heterostructures were epitaxially grown and integrated with buffered silicon substrates, by pulsed laser deposition technique, under the domain matching epitaxy paradigm. Whereas our earlier reports1,2 were confined only to in-plane (IP) magnetic properties of BFO/SRO and LCMO/SRO heterostructures, we further the same to out-of-plane (OOP) magnetic measurements here. In this paper, we will compare and contrast the magnetic properties in both IP and OOP configurations of BFO/SRO and LCMO/SRO heterostructures measured at different temperatures of 5,200, and 300 K using SQUID and VSM magnetometry. We have observed a contrasting variation in the magnetization behavior of these two heterostructures when the magnetic field was applied IP and OOP. Strong perpendicular magnetic anisotropy was observed in both the heterostructures.
1Singamaneni et al., MRS Advances, 1, 597 (2016); 2MRS Communications, 6, 234, (2016)
8:00 PM - EM02.03.02
A C-Band Integrated Tunable Bandstop Filter Using Self-Biased FeGaB/Al2O3 Multilayer Thin Film
Yifan He 1 , Yuan Gao 2 , Huaihao Chen 1 , Hwaider Lin 1 , Yuyi Wei 1 , Xi Yang 3 1 , Nian Sun 1
1 , Northeastern University, Boston, Massachusetts, United States, 2 , Winchester Technologies, LLC, Winchester, Massachusetts, United States, 3 Center of Microwave and Millimeter-Wave Technology, Beijing Institute of Technology, Beijing, Beijing, China
Show AbstractIn modern RF/microwave communication system, low-loss, lightweight and low-cost bandstop filter is highly demanded. To achieve reconfigurable subsystem in multi-band systems and radar systems, tunable RF/microwave bandstop filter is necessary. In this work, a C-band tunable bandstop filter device is designed, fabricated and tested. The device architecture is designed with a single transmission line on top of a narrow magnetic film ribbon. The magnetic film is a multilayer FeGaB/Al2O3 film with 25 nm and 5 nm thickness, respectively, and a total period of 8. The FeGaB material exhibits a low ferromagnetic resonance linewidth of 25 Oe, which gives rise to a potential candidate for RF/microwave application. Compared to the single layer magnetic film, the multilayer film has lower eddy current loss and out-of-plane anisotropy. The device performs a self-biasing resonance at C-band by taking the advantage from the shape anisotropy of a long FeGaB/Al2O3 multilayer ribbon. The self-biasing frequency of the bandstop filter appears at 5 GHz with an attenuation of over 20 dB. The stop band central frequency can also be magnetically tuned up to 8.5 GHz (70% tunability) with an attenuation of over 45dB by applying a modest external magnetic field of less than 400 Oe. The power handling capability under various magnetic biases is measured, which gives a maximum IP1dB of 3.7 dBm under zero bias field.
8:00 PM - EM02.03.03
Fabrication and Properties of Multiferroic PZT-Bi:RIG Composite Structure for Voltage-Driven Magneto-Optical Spatial Light Modulator
Naoki Akiyama 1 , Taichi Goto 1 2 , Hiroyuki Takagi 1 , Yuichi Nakamura 1 , Pang Boey Lim 1 , Hironaga Uchida 1 , Mitsuteru Inoue 1
1 Department of Electric and Electronic Information Engineering, Toyohashi University of Technology, Toyohashi Japan, 2 , JST PRESTO, Kawaguchi Japan
Show AbstractSpatial light modulators (SLMs) are devices to control the amplitude, phase and polarization of light and are an important component of such as optical communication systems. A magneto-optic SLM (MOSLM) using Faraday rotation for light modulation shows high switching speeds and robustness. There are two types of MOSLM to modulate Faraday rotation; one is driven by current for applying the magnetic field to change direction of magnetization while continuous drive is difficult due to large power consumption. The other is driven by voltage through inverse magnetostriction effect using piezoelectric materials, in which magnetic and piezoelectric materials composites are used to control the magnetization by applying mechanical stress in piezoelectric parts of the composite, and this results low power consumption. A prototype voltage driven MOSLM with multilayer structure composed of PbZr0.52Ti0.48O3 (PZT) and bismuth substituted rare earth iron garnet (Bi:RIG) was reported.[1] In this structure, the distortion thickness of magnetic material is limited since the stress by piezoelectric material is applied on the surface of Bi:RIG. So, the MO modulation cannot increase by increasing thickness of the magnetic material. To overcome this issue, 1-3 vertical pillar multiferroic composite structures are favorable. In this structure, magnetic pillars could be uniformly distorted by surrounded piezoelectric matrix, and large MO modulation will be obtained even in thick composites. In this work, we investigated stress distribution in the pillar using finite element method (FEM) to design desirable structure of the composite, and pillar structures composed of Bi:RIG and PZT were fabricated to see the MO modulation by voltage.
FEM results showed that the aspect ratio of pillar height, h, to width, w, is important to determine the stress distribution in magnetic pillar. In the case of h/w ratio smaller than 1, large stress is applied only near the interface, and stress distribution exists in-plane. So the h/w ratio higher than 3 is desired to achieve in-plane uniform stress. To see the validity of the simulation, composite samples were fabricated with etching process. Bi:RIG and PZT were used as the magnetic and piezoelectric materials, respectively. A 800 nm thick Bi:RIG layer was deposited on the substrate with bottom electrode by rf-sputtering. Bi:RIG pillers with 3 and 5 microns square were formed with electron beam patterning followed by etching process, and PZT was formed using metal organic decomposition method. Ferroelectric properties of fabricated pillar structure were measured, and the remanent polarization value of 27.4 μC/cm2 after applying 700 kV/cm was obtained in the composite and is as high as that of single PZT film (21.9 μC/cm2). MO modulation by voltage will be also reported.
This work was supported in part by the Grants-in-Aid for Scientific Research (S) 26220902 and (B) 16H04329.
[1] H. Takagi, et al. J. Magn. Soc. Jpn, 30 (2006) 581.
8:00 PM - EM02.03.04
Synthesis of Ca and F Co-Doped LaFeAsO, as a Mother Compound of Iron-Based Superconductors
Kodai Kaneyasu 1 , Masanori Matoba 1 , Yoichi Kamihara 1
1 , Keio University, Kanagawa Japan
Show AbstractA layered mixed anion compound LaFeAsO1-xFx, which exhibits superconductivity with Tc at 26 K, was discovered in 2008. This discovery has a strong impact due to relatively high Tc reaching 26 K, having broken a widely accepted belief that iron is antagonistic against high Tc superconductivity. After the discovery of LaFeAsO1-xFx, the Tc in iron-based superconductor have reached 58.1 K in SmFeAsO1-xFx under ambient pressure [M. Fujioka, et al. Supercond. Sci. Technol. 26, 850223 (2013)].
Superconductivity is observed for LaFeAsO1-xFx(x > 0.035) [Y. Kamihara, et al. J. Am. Chem. Soc. 130, 3296 (2008).]. Increasing x is a critical factor for an appearance of Tc. We demonstrate the stability of Ca and F-doped LaFeAsO (La1-xCaxFeAsO1-xFx) by density functional theory (DFT) calculations and experimental synthesis.
DFT calculations were performed using Vienna Ab−initio Simulation Package (VASP) code. Provided an assumed supercell as La3Ca1Fe4As4O3F1 for La1-xCaxFeAsO1-xFx (x = 0.25), the crystallographic lattice relaxation of La3Ca1Fe4As4O3F1 supercell was simulated. The relationship between lattice constants and internal energy was obtained. La1-xCaxFeAsO1-xFx(x = 0.25) per unit cell at T = 0 K is most stable at a = 0.397892 nm, b = 0.395636 nm, c = 0.859256 nm, and this belongs to orthorhombic. Lattice constants and lattice volume are smaller than LaFeAsO. It was assumed that starting materials were LaAs, FeAs, Fe2As, La2O3, CaO and CaF2, and we calculated the enthalpy of formation for La1-xCaxFeAsO1-xFx(x = 0 and 0.25). The enthalpy of formation for La1-xCaxFeAsO1-xFx(x = 0 and 0.25) are -21.7 kJ/mol and -19.5 kJ/mol. La1-xCaxFeAsO1-xFx(x = 0 and 0.25) is more stable than the starting materials.
Polycrystalline La1-xCaxFeAsO1-xFx (nominal x = 0.25 and 0.50) samples were synthesized by solid-state reaction. Grinding and weighing procedures were done in Ar atmosphere. LaAs, FeAs and Fe2As were prepared by heating stoichiometric mixtures of La, Fe and As in evacuated silica tubes. Then, La1-xCaxFeAsO1-xFx were synthesized by heating stoichiometric mixtures of LaAs, FeAs, Fe2As, La2O3, CaO and CaF2 powders in evacuated silica tubes at 1000 °C. Nominal x = 0.25 sample was heated for 10 h. Nominal x = 0.50 samples were heated for 10 h or 40 h. The crystallographic phases of samples were examined by powder X-ray diffraction (XRD) (Rigaku RINT2500 Ultra18) using Cu Ka radiation. Main peaks of XRD patterns were assigned to those of LaFeAsO phase. Lattice constants of these samples were calculated by least squares method. These samples belong to tetragonal, and the lattice constant and lattice volume of nominal x = 0.25 sample are a = 0.402104(9) nm, c = 0.87299(1) nm and V = 0.141152(7) nm3.
These lattice constants were smaller than those of LaFeAsO1-xFx. This result is consistent with that obtained by DFT calculations.
8:00 PM - EM02.03.05
A High-Sensitivity Zero-Biased Magnetoelectric Sensor Based on FeCoV/Terfenol-D/Pb(Zr1-x,Tix)O3/Terfenol-D/FeCoV Five-Phase Laminate Composites
Jing Qiu 1 , Xiaosheng Tang 1 , Wei Hu 1 , Zhenghao Li 1
1 , Chongqing University, Chongqing China
Show AbstractStrong magnetoelectric (ME) coupling effect has attracted continuously increasing interest in the past decades, owing to their potential applications in magnetic field sensors, current sensors, magnetic storages and energy harvesters, etc. However, in order to obtain high ME coupling effect, an external dc bias magnetic field (Hdc) is indispensable to ME laminated composites. And then, the sensor sizes and costs will increase sharply. To overcome these limitations, the zero-biased miniature ME sensor has become a hot research topic in recent years . Due to the establishment of an internal magnetic bias of the magnetostrictive materials in ME laminate composites, the nanocrystalline soft magnetic FeCoV alloy could be a good solution. In this paper, a novel high-sensitivity zero-biased ME sensor consists of FeCoV/Terfenol-D/Pb(Zr1-x,Tix)O3(PZT)/Terfenol-D/FeCoV (FMPMF) is presented, whose magnetoelectric coupling characteristics and sensing performance have been investigated. Compared to traditional Terfenol-D/PZT/Terfenol-D (MPM) sensor, the ME coupling characteristics of FMPMF sensor were significantly improved. Meanwhile, the induced zero-biased ME voltage of FMPMF sensor shows an excellent linear relationship to ac magnetic field both at the low frequency (1kHz) and the resonant frequency (115.14 kHz). The measured sensitivity at resonance is 1.95 V/Oe and the output resolution is approximately 2.43×10-8 T. The proposed FMPMF sensors still have very good performance in the current sensing. The measured results shows an average sensitivity of 1.14 mV/A with highly linear behavior in the current range 1 A to 10 A at 50 Hz. Remarkably, it indicates that the proposed zero-biased miniature ME sensor give the prospect of being able to applied to the field of highly sensitive current sensing for the electricity monitoring in electric power grid.
8:00 PM - EM02.03.06
Structural and Magnetic Properties of Strained, Anisotropic Fe-Co/Au-Cu Multilayers Using Combinatorial Deposition Methods
Georgios Giannopoulos 1 , Ruslan Salikhov 2 , G. Varvaro 3 , V. Psycharis 1 , A. Testa 3 , Michael Farle 2 , D. Niarchos 1
1 INN, NCSR Demokritos, Athens Greece, 2 Faculty of Physics and Center for Nanointegration (CENIDE), University of Duisburg-Essen, Duisburg Germany, 3 nM2-Lab, ISM-CNR, Rome Italy
Show AbstractCombinatorial sputtering technique was used to deposit and characterize alloys with different stoichiometries. This approach is a revolutionary step forward in the development of new materials. It involves the development and application of new tools for systematic and parallel synthesis and characterization of binary and ternary systems, thus being a very effective way to explore variable alloys stoichiometry. Moreover we used high throughput structural characterization methods to characterize a whole materials library in a single step procedure.
In order to create an alternative approach to rare earth permanent magnets, we employed FeCo since it can support high magnetic moment along with relatively high magnetocrystalline anisotropy. Moreover high coercivity is needed for a permanent magnet, since it is related to the energy product of the system.
Anisotropic behavior was induced into FeCo layer through AuCu underlayer, by straining the FeCo unit cell [2]. For this reason we performed combinatorial depositions of variable stoichiometry of Au-Cu alloy at 300oC in order to ensure the optimum lattice mismatch with the Fe-Co layer. A vast range of stoichiometry varying from Au10Cu90 to Au90Cu10 was explored. On the underlayer we deposited different stoichiometry of FeCo alloy and after optimization we used Fe45Co55 as the composition of the magnetic material layer. We also doped FeCo with Carbon since by this way we can stabilize strain and increase the magnetocrystalline anisotropy value [3]. We deposited up to 3nm FeCo on the buffer to prevent strain relaxation. Furthermore we also used an additional approach with alternate magnetic and non-magnetic thin layers (FeCo 1-3nm/AuCu 1-3nm) on single crystalline MgO (100) substrates to study the structural and magnetic properties.
High-throughput XRD measurements were contacted on Rigaku SmartLab, while, SQUID, vector-VSM and FMR measurements were also performed. A peak shift greater than 0.5o in the X-rays pattern compared to the theoretically expected value for FeCo-C alloy, was an indication of tetragonal distortion in all different cases.
A high magnetocrystalline anisotropy value of about 1 MJ/m3 was measured using FMR method [3]. A coercivity between 0.5 and 0.8 kOe was measured along with anisotropic behaviour in the magnetic properties of the system, which is considered as a step forward to potential application in nanoscale magnetism
Acknowledgements
We acknowledge funding of the EU through FP7-REFREEPERMAG
References
[1] X.-D. Xiang, X.-D Sun et al, Science (1995) p. 1738
[2] T. Burkert, L. Nordström, O. Eriksson, and O. Heinonen , Physical Rev. Lett. 93, 027203 (2004)
[3] G. Giannopoulos, R. Salikhov, B. Zingsem, A. Markou, I. Panagiotopoulos, V. Psycharis, M. Farle, and D. Niarchos, APL Materials 3,041103 (2015)
8:00 PM - EM02.03.08
Nonlinear Optical Diagnostic of Doped BiFe0,9Cr0,1O3 and BiFe0,9Al0,1O3 Multiferroics
H. Zaarour 2 , O. Idrissi 2 , N. Hassanain 2 , A. Belayachi 2 , M. Taibi 2 , M. Abd-Lefdil 1 2 , Katarzyna Ozga 1 , J. Jedryka 1 , Iwan Kityk 1
2 , MANAPSE, Energy Center, Faculty of Sciences, University of Mohammed V, Rabat Morocco, 1 , Institute of Optoelectronics and Measuring Systems, Faculty of Electrical Engineering, Czestochowa University of Technology, Czestochowa Poland
Show AbstractNonlinear Optical Diagnostic Of Doped BiFe0,9Cr0,1O3 And BiFe0,9Al0,1O3 Multiferroics
H. Zaarour: O. Idrissi,.M. Hassanain:, A. Belayachi, M. Taibi
MANAPSE, Energy Center, Faculty of Sciences, University of Mohammed V- Rabat, Morocco
M. Abd-Lefdil, K.Ozga, I.V.Kityk,, J.Jedryka
Institute of Optoelectronics and Measuring Systems, Faculty of Electrical Engineering, Czestochowa university of Technology, Armii Krajowej 17, Czestochowa , Poland
Multiferroics are a group of ferroics materials that exhibit simultaneously at least two types of physical phases, e.g. the ferromagnetic and ferroelectric states. React and respond to the greater number of external fields thereby creates a greater range of applications. Generally multiferroics are spatially and temporally asymmetric. The reason for this is the existence of two parameters of spontaneous long-range ordering. According to the classification two types of multiferroics. BiFeO3 material is selected from materials of the first type. Normally these materials are considered as weak ferromagnetic compounds. One of the primary objectives of the research materials of the first type is to enhance the coupling between electric and magnetic subsystems. One possibility of their more wider application is to perform their doping. Generally the doping causes distortion of the crystallographic network which may be effectively monitored by the nonlinear optics properties. In the presented report we will deal with BiFe0,9Cr0,1O3 and BiFe0,9Al0,1O3 . . These materials are fabricated in many different forms: from the solid materials to layers. In this paper well known multiferroic BiFeO3 was doped by Al and Cr. The objective of the study was to investigate the effect of doping the above-mentioned elements on the magnetic and non-linear optical properties of BiFe0,9Cr0,1O3 and BiFe0,9Al0,1O3 ceramics. So using the nonlinear optical method we would like to clarify the mechanisms of magnetoelectric coupling.
BiFe0,9Cr0,1O3 and BiFe0,9Al0,1O3 were synthesized by solid state reaction method using Bi2O3, Fe2O3, Cr2O3 and Al2O3 as a precursors. According to the required stoichiometry, the powders were weighed, mixed in an agate mortar and ground in order to get a homogeneous mixture. The mixture was placed in a platinum crucible and annealed.
In case of testing with the task of checking whether the samples are generate the second harmonic signal satisfactory results for BiFe0,9Al0,1O3 and BiFe0,9Cr0,1O3 samples were obtained. For the SHG signal BiFe0,9Al0,1O3 sample was characterized by a higher SHG intensity with respect to the BiFe0,9Cr0,1O3 sample. Larger it was also the time delay for the SHG signal. For the BiFe0,9Al0,1O3 sample was 6 ns and for BiFe0,9Cr0,1O3 sample 5.6 ns.
The full width at half maximum FWHM for BiFe0,9Al0,1O3 amounted to 30 ns and for BiFe0,9Cr0,1O3 28 ns. Following the obtained parameters of the SHG kinetics we try to find a correlation with degree of magnetoelectric interaction
8:00 PM - EM02.03.09
Multiferroic Epitaxial BiFeO3-CoFe2O4 Nanocomposite Thin Films Grown by RF Magnetron Sputtering
Tae Cheol Kim 1 , Seung Han Lee 1 , Shuchi Ojha 2 , C. A. Ross 2 , Dong Hun Kim 1
1 , Myongji University, Yongin Korea (the Republic of), 2 , MIT, Cambridge, Massachusetts, United States
Show AbstractSelf-assembled multiferroic nanocomposite films, in which magnetic spinel pillars grow epitaxially in a ferroelectric matrix, have been explored for their magnetoelectric properties and for potential applications in memory or logic devices. The strain coupling at the vertical spinel/ perovskite interfaces plays an important role in manipulating the magnetic, ferroelectric and multiferroic properties.
To date, these nanocomposites have been exclusively grown on single crystal oxide substrates using pulsed laser deposition (PLD). PLD is a versatile epitaxial thin film growth method but is limited in its ability to uniformly coat large areas due to the limited plume size. In this study, we describe the fabrication of self-assembled nanocomposites consisting of spinel CoFe2O4 (CFO) and perovskite BiFeO3 (BFO) on a SrTiO3 (STO) (100) substrate using radio frequency magnetron sputtering, which provides a low-cost and large-scale scalable manufacturing method. Films were grown at 500 – 650C substrate temperature in 50 mTorr of Ar/oxygen.
From the x-ray diffraction and SEM analysis, the CFO formed as epitaxial pillars ~20 nm diameter with rectangular cross-section and {110} vertical interfaces within a BFO matrix, similar to nanocomposites grown by PLD. However, an unusual tetragonal BFO phase was observed in films made with lower oxygen flow rates, unlike the rhombohedral BFO in PLD grown films on STO. Phi scans showed cube-on-cube epitaxial growth of CFO and BFO on STO, and reciprocal space maps indicated partial relaxation of the in-plane strain of the BFO. The magnetic hysteresis loop of the nanocomposite showed a strong anisotropy with out-of-plane easy axis as a result of both the shape anisotropy of the pillars and the dominant magnetoelastic anisotropy of the CFO. According to PFM (piezoresponse force microscopy), the BFO matrix exhibited ferroelectric domains.
8:00 PM - EM02.03.11
Photovoltaic Performance and Photoinduced Changes in Hysteresis Loop of Ferroelectric BiFeO3-SrTiO3 Thin Films
Haomin Xu 1 , Hao Pan 1 , Ji Ma 1
1 School of Materials Science and Engineering, Tsinghua University, Beijing China
Show AbstractThe interaction between photoresponse and ferroelectricity in photoferroelectric materials are widely studied. Here, we prepared 5%Mn-doped xBiFeO3-(1-x)SrTiO3 (BxFSTO, x=0.7, 0.55, 0.4) solid solution thin films on (001) SrTiO3 single crystal substrates via pulsed laser deposition method. All the films are fully crystalized as a pure-phase perovskite with highly c-axis oriented. B0.55FSTO film displayed best photoresponse ability with 0.1 V open circuit voltage and 0.5 μA/cm2 short circuit current density compared to B0.7FSTO and B0.4FSTO films. The photovoltaic effect of the films varied when the films were switched by ±15V voltage and reoriented the ferroelectric domains. It was also observed that the polarization-electric hysteresis loop changed when film was illuminated under full spectrum light due to the light induced polarization. These results reveal intriguing signal processing and solar light conversion applications in ferroelectrics.
8:00 PM - EM02.03.12
Electric Field Control of Induced Magnetization in the Extrinsic Multiferroic System (1-x)(Ba,Ca)(Zr,Ti)O3-xNiFe2O4
Muhammad Naveed-Ul-Haq 2 , Vladimir V. Shvartsman 2 , Harsh Trivedi 2 , Soma Salamon 1 , Samira Webers 1 , Heiko Wende 1 , Doru Lupascu 2
2 , Institute for Materials Science and Center for Nano-Integration (CENIDE), University of Duisburg-Essen, Essen, Nordrhein-Westfalen (NRW), Germany, 1 , Faculty of Physics and Center for Nano-Integration (CENIDE), University of Duisburg-Essen, Duisburg, Nordrhein-Westfalen (NRW), Germany
Show AbstractMagnetoelectricity can manifest itself in two ways: Either electric polarization can be controlled with magnetic field (the direct magnetoelectric effect), or the induced magnetization can be manipulated by an electric field (the converse magnetoelectric effect). We explore converse magnetoelectricity in an extrinsic multiferroic system comprising of an excellent piezoelectric (Ba,Ca)(Zr,Ti)O3, and NiFe2O4 which has good magnetostrictive properties. We have synthesized four compositions consisting of (1-x)(Ba,Ca)(Zr,Ti)O3-xNiFe2O4 where x = 0.2, 0.3, 0.4, and 0.5 employing solid state synthesis. Analysis of x-ray diffraction data with Rietveld refinement technique revealed that all samples have pure phase. Macroscopic electric and magnetic studies were conducted along with microscopic studies like piezoresponse force microscopy (PFM) and magneto-force microscopy (MFM) to verify the multiferroic nature of the samples. All the samples show simultaneous existence of ferroelectricity and ferromagnetism. Converse magnetoelectric coupling was measured, and all of them were found to possess decent converse magnetoelectric coefficients. The sample 0.7(Ba,Ca)(Zr,Ti)O3-0.3NiFe2O4 shows the best properties among these possessing the highest converse magnetoelectric coefficient with a value of 45 ps/m. This value is almost twice larger than previously reported for 0-3 (3-3) connectivity samples synthesized with similar methods.
8:00 PM - EM02.03.13
Size-Dependent Magnetic Properties of FeGaB/Al2O3 Multilayer Micro-Islands
Xinjun Wang 1 , Huaihao Chen 1 , Yuyi Wei 1 , Xianfeng Liang 1 , Nian Sun 1
1 Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts, United States
Show AbstractRecently, micro-size patterned magnetic materials are widely used for MEMS devices. However, self-demagnetizing action is significantly influencing the performance of the magnetic material in many MEMS devices. An experimental study of magnetic properties in lift-off patterned micro-scale FeGaB/Al2O3 multilayer is reported. Hysteresis loop, ferromagnetic resonance (FMR), permeability and domain behavior have been demonstrated by complementary techniques. The comparisons among micro-islands with different sizes in the range of 200μm~500μm as well as full film show a marked influence of the demagnetizing field inside the islands.
8:00 PM - EM02.03.14
Deterministic Control of Cationic Distribution by Strain in Multiferroic Bi5Ti3FeO5 Films
Changhee Sohn 1 , Dongkyu Lee 1 , Xiang Gao 1 , Hu Young Jeong 2 , Young-Min Kim 3 , Ho Nyung Lee 1
1 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 , Ulsan National Institute of Science and Technology, Ulsan Korea (the Republic of), 3 , Sungkyunkwan University , Suwon Korea (the Republic of)
Show AbstractStrain engineering has been a powerful way to improve or to develop novel functionalities of materials by modulating the bond angle/length between atoms as well as inducing defects. Beyond these well-known mechanisms, a recent theoretic calculation predicted that strain engineering can even control the cation distribution of ions in the well-known Aurivillius multiferroic system, Bi5Ti3FeO15 (Bi4Ti3O12+BiFeO3) [A. Y. Birenbaum and C. Ederer, Appl. Phys. Lett. 108, 082903 (2016)]; while Ti and Fe ions are randomly distributed in bulk, Fe ions can preferentially locate at the inner or outer octahedral layers in the Aurivillius structure depending on the type of strain. To attest the prediction, we have fabricated Bi5Ti3FeO15 epitaxial films on LaAlO3, LSAT, and SrTiO3 substrate by using pulsed laser epitaxy. These substrates allow us to control both the sign and degree of strain (-0.94 ~ 1.20 %). Scanning transmission electron microscopy with energy dispersive x-ray spectroscopy revealed that Fe ions have site-preference when compressively strained, whereas no preferential positioning was observed in the tensile strained films. This experimental result supports well the theoretical prediction particularly for the case of compression, while further theoretical and experimental attempts are required for the tensile case. Effects of the site preference on magnetic and ferroelectric properties were investigated by using SQUID and second harmonic generation and will be discussed.
This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.
8:00 PM - EM02.03.15
Near-Room Temperature Non-Aqueous Synthesis of Iron Doped BaTiO3 for Multiferroic Memory Devices
Julien Lombardi 1 2 , Stephen O'Brien 1 2
1 , City College of New York, New York, New York, United States, 2 Chemistry, The City University of New York, New York, New York, United States
Show AbstractMaterials that exhibit ferroelectric and ferromagnetic properties simultaneously have attracted attention of many researchers in the fields of information storage, spintronics, and multiple-state memory storage devices. The coexistence of these two orderings brings out novel physical phenomena that can be used for new device functions. Having the simultaneous cross coupling between magnetic and electric orders will enable the control of ferromagnetic polarization by an electric field and vice versa. BaTiO3 (BTO), BaTi1-xFexO3 (BFT) x = 0.1-0.3, 0.5, and 0.75, and BaFeO3 (BFO) monodisperse nanoparticles were synthesized using the gel collection method at near room temperature (60°C). The effect of Fe doping on the dielectric and physical properties was studied systematically. X-Ray diffraction (XRD) and X-Ray photoelectron spectroscopy (XPS) confirmed that Fe2+ was successfully doped onto the B-site Ti4+ octahedron location in the crystal lattice. Transmission electron microscopy (TEM) imaging confirmed the average size of the nanocrystals to be ~8 nm and were monodisperse and uniform in morphology and size. Impedance analysis of 0-3 thin film nanocomposites of BTO, BFT, and BFO filler particles in a polyvinylpyrrolidone (PVP) matrix showed a decrease in effective dielectric constant with an increase in Fe2+ dopant concentration. A range of 0.02-0.09 was recorded for the dielectric loss tangent measurements. The decrease in effective dielectric constant is attributed to the doping of Fe2+ on the Ti4+ B-site creating fewer polarizable dipoles within the crystal unit cell.
8:00 PM - EM02.03.16
Single Phase Multiferroic—Fe Substituted Gd-Chromite [GdFe0.5Cr0.5O3] Thin Films
Jianhang Shi 1 , Shiqi Yin 2 , Menka Jain 2 3
1 Department of Material Science and Engineering, University of Connecticut, Storrs, Connecticut, United States, 2 Department of Physics, University of Connecticut, Storrs, Connecticut, United States, 3 Institute of Material Science, University of Connecticut, Storrs, Connecticut, United States
Show AbstractMultiferroic materials, which exhibit at least two ferroic orders [(anti)ferromagnetic, ferroelectric and ferroelastic], show rich physical properties and have been a topic of great interest to researchers during recent years. Among them the coexistence of simultaneous magnetic and ferroelectric ordering is highly desired as they offer the possibility to switch polarization by the application of an external magnetic field and vice versa. It is this aspect of electrical control of magnetism and magnetic control of ferroelectricity that could potentially lead to a number of new devices within the framework of information storage, communication and spintronics. From a practical point of view of integrating into the existing processing technologies, it is desirable to obtain multiferroic materials in the form of thin films. To date, creating high quality single phase multiferroic films is still challenging and only a few have been reported based on hexagonal manganites and Bi- or Pb-based perovskites. Rare earth chromites are of particular interest, since they hold promise for high magnetoelectric coupling. Here we present synthesis of a new single-phase multiferroic thin film based on iron substituted gadolinium chromites. Polycrystalline GdFe0.5Cr0.5O3 thin films have been prepared by a chemical solution deposition method on Pt/TiO2/SiO2/Si substrates and their structural, electrical, and magnetic properties have been studied. A ferroelectric loop is obtained by P-E hysteresis curves with a remnant polarization of 0.82 μC cm-2 at room temperature indicating a ferroelectric behavior. In addition to the ferroelectricity, the ferromagnetic behavior of the film is also observed, which could be explained by the canted-antiferromagnetism. This work bears novelty as it is the first time that data of multiferroic films of iron doped gadolinium chromites is reported, and validates chemical solution deposition as a facile and versatile method in exploring new multiferroic materials.
8:00 PM - EM02.03.17
Synthesis of NiFe Nanoparticles and Subsequent Coating with Au Shells as Magnetically-Active Spectroscopic Nanoprobes
Yan Liu 2 1 , Jing Li 1 , Zakiya Skeete 1 , Ning Kang 1 , Shan Yan 1 , Chuan-Jian Zhong 1
2 , Northeastern University, Shenyang China, 1 , State University of New York at Binghamton, Binghamton, New York, United States
Show AbstractMagnetic nanoparticles have found a wide range of applications, but many of the applications require the control of the surface properties of the magnetic nanoparticles so that they are functional or compatitble in the desired medium for a specific application. One important pathway towards the control of the surface properties involves coating of the nanoparticles with a shell of metals such as gold and silver, which can be used for biosensing or spectroscopic application because of the well-known surface binding chemistry of such metals, biocompatability, and optical properties. This report describes recent findings of an investigation of the synthesis if Ni39Fe61 alloy nanoparticles and the subsequent coating with Au shells. Results from the characterizations of the changes in the nanoparticle composition, surface plasmon resonance, surface functionalization and magnetic-responsive properties provided the formation for assessing the core-shell type nanostructure. The exploitation of such Ni39Fe61@Au nanoparticles as nanoprobes for surface enhanced Raman scattering detection of biomolecules attached to the surface of the nanoparticles and biomolecular separation in solutions will also be discussed.
8:00 PM - EM02.03.18
Ferroelectricity and Magnetism of Multiferroic Hexagonal ScFeO3 Films
Yosuke Hamasaki 1 , Shintaro Yasui 1 , Tomoyasu Taniyama 1 , Mitsuru Itoh 1
1 , Tokyo Institute of Technology, Yokohama Japan
Show AbstractIt is well known that ReFeO3 (Re = Rare earth element) have orthorhombic perovskite structure as a stable phase. Hexagonal ReFeO3 (h-ReFeO3) which is isostructural with ferroelectric YMnO3 (Tc ~ 1000K) is also reported as a metastable phase. Due to the strong magnetic interactions between Fe3+ cations, the higher magnetic order temperature compared with hexagonal manganites is expected in h-ReFeO3. A magnetic phase transition temperature of h-ReFeO3 increases with decreasing ionic radius of Re cation. h-ReFeO3 which consists of small ionic Re cation is a candidate for a high temperature multiferroic material.
Thus, we focused on h-ScFeO3 because an ionic radius of Sc is smallest in rare earth element.
Metastable h-ReFeO3 were obtained by containerless melt crystallization process and crystallization from amorphous phase. Masui et. al. prepared Sc substituted LuFeO3 by containerless process, and h-Lu1-xScxFeO3 was obtained in the range of x = 0 - 0.8. h-ReFeO3 (Re = Tb-Lu, Y ) were stabilized on substrates such as YSZ(111) and Pt(111)/Al2O3(0001) in film form by pulsed laser deposition (PLD) and sputter techniques. However, preparation of h-ScFeO3 have not been reported yet. In this study, we attempted to stabilize h-ScFeO3 in film form and investigated their physical properties.
h-ScFeO3 was deposited on various substrates such as Al2O3(0001), YSZ(111), SrTiO3(111) substrates by PLD technique. h-ScFeO3 was only grown on Al2O3(0001) substrate. Crystal structure of film was characterized by X-ray diffraction (XRD) and scanning transmission electron microscope (STEM). XRD measurements revealed that h-ScFeO3 was epitaxially grown with the relationships of ScFeO3(0001)//Al2O3(0001). Here, h-ReFeO3 have a possibility of three crystal structures; one polar (S.G. P63cm) and two nonpolar (S.G. P63/mmc and P-3c) structures. It is difficult to distinguish three structures by XRD measurement. In order to determine detail of crystal structure, we performed STEM observation. STEM observation revealed that the atomic displaced pattern of Re cations is up-up-down or down-down-up which is correspond to that of polar structure with S.G. P63cm. Therefore, we have succeeded in stabilization of polar h-ScFeO3 at first time.
Ferroelectricity of h-ScFeO3 film was evaluated through polarization vs electric filed (P-E) hysteresis loop using Pt/h-ScFeO3/LaSrMnO3 capacitor structure. The remanent polarization of ~3 μC/cm2 is observed at room temperature, which is comparable that of YMnO3.
Magnetism and ferroelectric domain structure in h-ScFeO3 film will be also discussed.
8:00 PM - EM02.03.19
Effect of Surfactants on Morphology and Physical Properties of BiFeO3 Synthesized by Microwave-Assisted Hydrothermal Method
Marcio Curvello 1 , Midilane Medina 1 , Alessandra Zenatti 1 , Marcia Escote 1
1 , University of ABC, Santo Andre Brazil
Show AbstractMultiferroic materials have been extensively studied due to their important physical properties. These compounds exhibit simultaneous electric and magnetic ordering when applied electric and/or magnetic fields. Among these materials, BiFeO3 (BFO) compound is one of the few known materials that present this effect at room temperature and is a very promising material to apply in multifunctional devices. Although, the amount of bismuth in such compounds can cause instability and create impurities that affect their electric conductivity, then, several works report the doping effect and alternative synthetic methods. A promising methodology is the hydrothermal techniques, which allowed synthesizing complex materials at lower processing temperature and time, with high purity. Microwave-assisted hydrothermal can also synthesized compounds in faster reaction with homogeneous nucleation of the particles. In this work, BiFeO3 nanostructures were synthesized under microwave hydrothermal condition with urea and cetyltrimetilammonium bromide (CTAB) as surfactant. We investigated the effect on the morphology and the structural properties on the samples synthesized by this method. The structural properties were analysed through X-ray powder diffraction (XRD) using a Bruker D8 X-ray Diffractometer. Images of Scanning arciElectron Microscopy (SEM) indicate that the urea and CTAB modify the shape and size of BFO particles to rods-like particles. The magnetic properties were characterized through magnetization measurements as a function of applied magnetic field and temperature. Such characterizations were carried out in MPMS SQUID VSM EverCool of Quantum Design. In addition, electrical properties have been characterizing through impedance spectroscopy in a Solartron system. The effect of the addition of CTAB and urea in the synthesis of BFO seems to modify the morphology of the samples and seems to affect their physical properties.
8:00 PM - EM02.03.20
Optimized Polymer-Based Magnetoelectric Materials for Magnetic and Current Sensing Devices
S Reis 1 , MP Silva 1 , V Correia 1 , P Martins 1 , Senentxu Lanceros-Mendez 1 2 3
1 , University of Minho, Braga Portugal, 2 , BC Materials, Bilbao Spain, 3 , Ikerbasque, Bilbao Spain
Show AbstractMagnetic sensors have become an essential measuring tool in a range of application areas including biomedicine, multimedia, automobile and military, just to mention some of them. The magnetoelectric (ME) effect is increasingly being considered an attractive alternative for magnetic field and current sensing, being able to sense static and dynamic magnetic fields.
In contrast with ceramic-based ME composites, polymer-based ME composites can be easily fabricated by conventional low temperature processing into a variety of forms, such as thin sheets or molded shapes and can exhibit improved mechanical properties, meeting the latest magnetic sensing market demands.
This work reports on the development and applicability of these materials as magnetic and current sensors, not only revealing and optimizing their magnetoelectric coupling, but also demonstrating their practical characteristics as magnetic field and current sensors. The sensors are developed based on PVDF/Metglas composites and the full scale input (FS), hysteresis, sensitivity, linearity and resolution of the sensors will be demonstrated and discussed. Further, the main characteristics and potential applicability of polymer composites based on isotropic and anisotropic magentostrictive magnetic nanoparticles within a piezoelectric polymer will be discussed.
Acknowledgements
The authors thank the FCT- Fundação para a Ciência e Tecnologia- for financial support in the framework of the Strategic Funding UID/FIS/04650/2013 and under project PTDC/EEI-SII/5582/2014. P.M., V.C., S.R. and M.S. acknowledges also support from FCT (SFRH/BPD/96227/2013, SFRH/BPD/97739/2013, SFRH/BDE/406 and SFRH/BD/70303/2010 grants respectively). Financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) (including the FEDER financial support) and from the Basque Government Industry Department under the ELKARTEK Program is also acknowledged.
Symposium Organizers
Nian Sun, Northeastern University
Franz Faupel, Kiel University
Cewen Nan, Tsinghua University
Ramamoorthy Ramesh, University of California, Berkeley
EM02.04: Magnetoelectrics II
Session Chairs
Jiamian Hu
Yayoi Takamura
Tuesday AM, November 28, 2017
Hynes, Level 1, Room 107
8:00 AM - *EM02.04.01
Mechano-Magneto-Electric (MME) Energy Harvesting
Shashank Priya 1 , Deepam Maurya 1 , Haribabu Palneedi 2 , Jungho Ryu 2
1 , Virginia Tech, Blacksburg, Virginia, United States, 2 , Korea Institute of Materials Science, Changwon Korea (the Republic of)
Show AbstractEnergy harvester design is platform dependent and requires considerable integration efforts. In the case of vibration energy harvesting, various forms of piezoelectric transducer structures have been fabricated to capture the mechanical energy with high efficiency. At micro-to-nanoscale, the design of transducer becomes challenging as the size reduction is accompanied by enhancement in the resonance frequency. We will review the solution to the problem of low frequency resonant transducer structures and demonstrate novel magnetoelectric harvesters that can capture mechanical energy and magnetic energy at the same time over a wide frequency regime. The mechano-magneto-electric energy harvester consisting of a magnetostrictive/ piezoelectric/ magnetostrictive laminate structure utilizes two mechanisms simultaneously: 1. magnetoelectric effect, where external magnetic field H can excite longitudinal strain through magnetostricitve phase and transfer to piezoelectric phase; 2. Piezoelectric effect, where induced mechanical vibration can create strain and generate charge. The presentation will cover recent advances made in synthesis of magnetoelectric laminate composites through combination of aerosol deposition and laser sintering. Interface design through controlled laser annealing has opened the opportunity to achieve high coupling factors responsible for high power density under dual field excitation. The results show that matching the interface mechanical impedance and imposing self-biased response is critical towards achieving high volumetric and power density.
8:30 AM - EM02.04.02
Ultra-Sensitive NEMS Magnetoelectric Sensor for Picotesla DC Magnetic Field Detection
Alexei Matyushov 1 , Menghui Li 1 , Cunzheng Dong 1 , Huaihao Chen 1 , Hwaider Lin 1 , Tianxiang Nan 1 2 , Zhenyun Qian 1 , Matteo Rinaldi 1 , Nian Sun 1
1 , Northeastern University, Boston, Massachusetts, United States, 2 , University of Wisconsin–Madison, Madison, Wisconsin, United States
Show AbstractWe report a highly sensitive NEMS DC/low frequency magnetic field sensor consisting of an AlN/FeGaB resonator, with a delta-E effect-based sensing principle. Unlike previously reported magnetic field detection schemes, such as monitoring impedance, or the voltage induced by the magnetoelectric effect, we designed a system to take advantage of the delta-E effect by measuring reflected output voltage from the sensor as a function of magnetic field. The AlN/FeGaB resonator shows a resonance frequency shift of 3.19 MHz (1.44%), which leads to a high DC magnetic field sensitivity of 2.8 Hz/nT and a limit of detection of 800pT in an unshielded, room temperature and pressure, lab environment.
8:45 AM - *EM02.04.03
The Influence of Shear on Strain-Mediated Magnetoelectric Effects
Neil Mathur 1
1 Materials Science, University of Cambridge, Cambridge United Kingdom
Show AbstractFerroelectric domain switching in PMN-PT substrates affects ferromagnetic films that are either grown or placed on top, but the effect of the shear strain associated with this switching has been hitherto overlooked. I will reveal the effect of this shear strain via magnetic XMCD-PEEM images from Diamond Light Source (UK).
9:15 AM - EM02.04.04
Magnetic Field Measurements by Surface Acoustic Wave Sensors
Anne Kittmann 1 , Sebastian Zabel 2 , Phillip Durdaut 3 , Erdem Yarar 1 , Dirk Meyners 1 , Michael Höft 3 , Reinhard Knöchel 3 , Franz Faupel 2 , Eckhard Quandt 1
1 Inorganic Functional Materials, Institute for Materials Science, Kiel Germany, 2 Multicomponent Materials, Institute for Materials Science, Kiel Germany, 3 Microwave Engineering, Institute of Electrical Engineering and Information Technology, Kiel Germany
Show AbstractLove-wave surface acoustic wave sensors are mainly used for measurements in liquids [1]. This type of surface acoustic wave sensors is based on shear waves instead of Rayleigh waves. Another application of these sensors can be the magnetic field measurement. A shear wave delay line configuration using magnetostrictive layers like FeCoSiB [2] on top of the delay line is demonstrated. The magnetic field changes the elastic coefficients of the magnetostrictive layer, and thus, has an effect on the wave propagation velocity of the surface acoustic wave. The altered velocity results in a magnetic field dependent relative phase change between a reference signal and the output signal of the delay line. A sensitivity of 600 °/mT is reached leading to a limit of detection of 250 pT/Hz1/2 at 10 Hz and 80 pT/Hz1/2 at 100 Hz. Typical for surface acoustic wave sensors the sensor shows a broad bandwidth above 1 MHz, which opens a wide range of application possibilities. The influences of different piezoelectric substrates and different magnetostrictive materials are discussed. The presented sensor concept is eminently suitable to measure weak magnetic fields with high bandwidth.
Funding by DFG (SFB 1261) and DARPA (BAA-15-19 MATRIX) is gratefully acknowledged.
[1] M. D. Schlensog, T. M. A. Gronewold, M. Tewes, M. Famulok, and E. Quandt, “A Love-wave biosensor using nucleic acids as ligands,” Sensors Actuators, B Chem., vol. 101, no. 3, pp. 308–315, 2004.
[2] H. Greve, E. Woltermann, H.-J. Quenzer, B. Wagner, and E. Quandt, “Giant magnetoelectric coefficients in (Fe90Co10)78Si12B10-AlN thin film composites,” Appl. Phys. Lett., vol. 96, no. 18, p. 182501, 2010.
9:30 AM - *EM02.04.05
Electric-Field Control of Tri-State Phase Transformation with Selective Dual-Ion Switch
Pu Yu 1
1 , Tsinghua University, Beijing China
Show AbstractElectric-field control of phase transformation with ion transfer is of great interest in materials science with enormous and important practical applications, such as batteries, smart windows, fuel cells, etc. Although increasing the number of the transport ion species and the corresponding controllable crystalline phases can greatly enrich the material functionalities, studies have so far targeted mainly on the evolution of only single ionic species (e.g. O2-, H+ or Li+, etc.). In this talk, I will present our recent progress on the reversible and nonvolatile electric-field control of dual-ion (O2 and H+) phase transformation associated with the discovery of the exotic tri-state electrochromic and magnetoelectric effects. These findings open up new opportunities for the electric-field control of multi-state phase transformation with novel crystalline structures and rich functionalities.
10:30 AM - *EM02.04.06
Next Generation Frequency Agile Electronic Materials Processing Tools Newly Developed at AFRL
Brandon Howe 1
1 , Air Force Research Laboratory, Wpafb, Ohio, United States
Show AbstractNext-generation warfighter electronics rely on the development of truly disruptive and robust electronic materials in order to enable game-changing advancements in RF/microwave performance and frequency-agility. The introduction of magnetic materials and voltage-tunable magnetic materials in RF/microwave systems is the most promising route to achieving such functionality. The general scientific community if extremely materials limited - both in the absolute number of materials to choose from as well as materials quality - and the major scientific challenge lies in the creation of novel materials and heterostructures with exceptionally high crystalline quality in order to unlock and explore unique and interesting properties. In order to accomplish this, one must create novel processing schemes in order to access never-before-achieved synthesis space, thus unlocking the ability to grow materials with properties far beyond conventional materials. Recently, at the Materials and Manufacturing Directorate at AFRL, we have built up a state-of-the-art PVD epitaxy suite capable of quickly scanning through an enlarged processing space in order to rapidly assess and identify novel materials with enhanced physical properties towards AF application. This talk will focus on the buildup and characterization of both a fully automated UHV pulsed laser epitaxy tool for the growth of high quality ferromagnetic oxides and oxide heterostructures as well as a truly one-of-a-kind and fully automated multifunctional epitaxial growth system (MEGS) capable of applying magnetic fields during both magnetron sputter epitaxy and pulsed laser deposition for creating complex metal/metal nitride/oxide heterostructures never before achieve. I will show how these systems are creating exceptionally high quality and novel magnetic oxides with record magnetic (magnetostriction) and microwave performance and transition metal nitrides for electrode interlayers necessary to provide robust alternatives for seeding the growth of high quality magnetic oxide overlayers. The nitrides grown by sputtering demonstrate properties among the best reported as well as reveal incredibly low roughness values and evidence of step-flow growth, while our novel AlNiZnFerrite material demonstrates record high magnetostriction while mitigating prohibitively large losses (microwave damping) and discuss how these properties can be controllably manipulated through strain engineering.
11:00 AM - EM02.04.07
Magnetoelectric Vibrational Energy Harvesters Utilizing a Phase Transitional Approach
Margo Staruch 1 , Jin-Hyeong Yoo 2 , Nicholas Jones 2 , Peter Finkel 1
1 , U.S. Naval Research Lab, Washington, District of Columbia, United States, 2 , Naval Surface Warfare Center Carderock, West Bethesda, Maryland, United States
Show AbstractMagnetoelectric hybrid energy harvesters, consisting of magnetostrictive FeGa (Galfenol) and single crystal relaxor ferroelectric Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT), have been studied and designed. An oscillating magnetic field produced from either vibrational or rotational motion is translated into a strain in the Galfenol. This strain is then transmitted to the piezocrystal, triggering an induced rhombohedral to orthorhombic phase transition in the (011) domain engineered PIN-PMN-PT crystal. Since this is a threshold phenomenon, the large jump in polarization produces an output voltage that is independent of frequency making this broadband energy harvesting device of interest for a wide range of non-resonant applications. A combination of modeling and component testing was performed, and a final device was realized. The modeling and testing results, as well as the performance of the composite harvester, will be presented.
11:15 AM - *EM02.04.08
Critical Role of Interface Strain in Physical Properties of Epitaxial Nanoscaffolding Ferroic Films
Aiping Chen 2 , OonJew Lee 4 , Jiamian Hu 3 , Ping Lu 5 , Wenrui Zhang 6 , Haiyan Wang 6 , Judith MacManus-Driscoll 4 , Long-Qing Chen 3 , Quanxi Jia 1
2 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 4 , University of Cambridge, Cambridge United Kingdom, 3 , The Pennsylvania State University, University Park, Pennsylvania, United States, 5 , Sandia National Laboratories, Albuquerque, New Mexico, United States, 6 , Purdue University, West Lafayette, Indiana, United States, 1 , State University of New York at Buffalo, Buffalo, New York, United States
Show AbstractStrain engineering provides a powerful approach to manipulating and/or enhancing the desired functionalities in a range of electronic materials, where the lattice strain in the interested film is most commonly introduced through heteroepitaxy. In correlated complex metal oxide films, however, an incorporation of a large lattice strain in a relatively thick film has been quite challenging. In this presentation, we will show that a large lattice strain in complex metal oxides could be accomplished in a much thicker film by using a configuration of epitaxial nanoscaffolding nanocomposites. Using both ferroelectric and ferromagnetic oxides as model systems, we have demonstrated that a lattice strain up to 2% could be achieved in films with thickness well above the critical film thickness. Importantly, we have illustrated that certain physical properties of the materials could be systematically tuned by controlling the strain state of the epitaxial nanoscaffolding films. Our phase field simulations have suggested that the ultimate strain in the interested phase is related to the vertical interfacial area and interfacial dislocation density of the epitaxial nanoscaffolding nanocomposite films.
11:45 AM - EM02.04.09
Huge Magnetostrictive Properties of SmFe and SmFeB Thin Films at Low Fields
Xianfeng Liang 1 , Cunzheng Dong 1
1 , Northeastern University, Boston, Massachusetts, United States
Show AbstractPiezomagnetic materials with large saturation magnetostriction constant at low saturation field, can lead to strong ME coupling in magnetoelectric heterostructures, which can be applied in various devices including ultra-high sensitive magnetic sensors, voltage tunable RF/microwave magnetic devices [1-2], etc. It is well known that rare-earth (R)-Fe based alloys exhibit very large magnetostriction at room temperature, referred to as giant magnetostriction [3-4]. The alloy TbFe2 is known to exhibit the largest positive magnetostriction, while SmFe2 has the largest negative magnetostriction [5]. In our work, the magnetostriction and the magnetic properties of amorphous Sm-Fe and Sm-Fe-B thin films were systematically investigated over a wide composition range from 19.3 to 90 at% Sm. In the case of Sm-Fe-B thin films, the power of B is varied from 30w to 180w. Good magnetostrictive characteristics, particularly at low magnetic fields, are achieved in both Sm-Fe and Sm-Fe-B thin films, although better properties are observed in Sm-Fe rather than Sm-Fe-B thin films. The properties of Sm-Fe-B films are decreased a little due to too much addition of B. At a magnetic field of 200 Oe, for example, the magnitude of magnetostriction is around 700 ppm in a Sm-Fe thin film and the piezomagnetic coefficient is up to 10 ppm/Oe, which is even larger than FeGaB of 8 ppm/Oe. With their excellent magnetostrictive characteristics, the present Sm-Fe and Sm-Fe-B thin films are considered to be potential candidates for tunable magnetoelectric microwave devices.
1. J. Lou, et al. Applied Physics Letters, 91,182504 (2007).
2. J. Lou, et al. Advanced Materials, 21, 4711 (2009).
3. M.I. Bichurin, et al. Physical Review B, 68, 054402 (2003).
4. N.C. Koon, et al. Physics Letters A, 37, 413 (1971).
5. A.E. Clark, et al. Ferromagnetic Materials, vol. 1, chap. 7 (1980).
EM02.05: Multiferroics II
Session Chairs
Lane Martin
Nicola Spaldin
Tuesday PM, November 28, 2017
Hynes, Level 1, Room 107
1:30 PM - *EM02.05.01
Strain, Defects and Alloying in BiFeO3 Thin Films—Towards Structure, Transport and Magnetism Control
Lane Martin 1
1 , University of California, Berkeley, Berkeley, California, United States
Show AbstractMaterials such as BiFeO3 have motivated a generation of scientists to dream of the exciting applications that could be realized by the further development of multiferroic and magnetoelectric materials. But, despite tireless efforts in the community to understand, manipulate, and, ultimately, utilize the innate properties of what has become the most widely studied multiferroic today, countless questions as to the fundamental nature of BiFeO3 remain. In turn, few materials can offer the paradigmatic combination of vast potential and excitement with a frustrating lack of utility and overall complexity that BiFeO3 can provide. Ultimately, such complex materials as BiFeO3 remain ensconced in our minds because they challenge our ability to exert control on materials as we desire.
In this talk, we will address up to three different aspects associated with controlling this complex material. First, application of BiFeO3 has been has been limited by its poor electrical resistivity. We have explored both chemical and defect-based routes to control the electrical properties of this system. We will highlight insights related to cation and anion non-stoichoimetry and defect-engineering approaches that can provide for improved electrical resistance and explore their effects on ferroelectric switching. Second, BiFeO3, which exhibits strong coupling between ferroelectric and antiferromagnetic order, has attracted significant attention due to its room-temperature multiferroism and potential for magnetoelectric effects. To achieve such functionality, it is critical to be able to control the antiferromagnetic spin structure in BiFeO3. Despite this critical need and sustained interest in this topic, there are few studies on the strain evolution of the antiferromagnetic structure in BiFeO3 thin films. Here, X-ray linear dichroism and first-principles calculations will reveal that epitaxial strain can be used to continuously tune the antiferromagnetic spin-axis orientation in BiFeO3 films across a wide angular space and thus control the magnetic anisotropy of an exchange-coupled ferromagnetic layer. We highlight an unexpected deviation of the classical perpendicular relationship between the antiferromagnetic axis and the polarization vector. First-principles calculations suggest that the magnetic anisotropy in is tunable with strain by leveraging the interplay between Dzyaloshinsky-Moriya interactions and single-ion-anisotropy. Finally, we will explore the potential of cation-alloying (namely with La) as a way to further manipulate and control the structural and magnetic order of BiFeO3. Early observations suggest the potential for structural competition and exotic magnetic order at high La-alloying levels.
2:00 PM - EM02.05.02
Room-Temperature Control of Magnetization and Non-Reciprocal Microwave Response Using Magnetoelectric Effect in Multiferroic Y-Type Hexaferrite
Sakyo Hirose 1 , Yusuke Iguchi 2 , Yoichi Nii 2 , Toru Asaka 3 , Tsuyoshi Kimura 4 , Yoshinori Onose 2
1 , Murata Manufacturing Co. Ltd, Nagaokakyo Japan, 2 Department of Basic Science, The University of Tokyo, Tokyo Japan, 3 Department of Materials Science and Engineering, Nagoya Institute of Technology, Nagoya Japan, 4 Department of Advanced Materials Science, The University of Tokyo, Kashiwa, Chiba, Japan
Show AbstractRecently, some ferrites including hexaferrites with magnetoplumbite-related hexagonal structures have been attracting considerable attention due to their magnetoelectric (ME) properties [1]. Such ME materials are very promising for realizing new functional devices with low energy consumption, such as a magnetization switch, non-volatile random access memory, and a microwave device controlled by an electric field. Although several materials were found to exhibit the ME effect, the operational temperatures of most materials were limited to temperatures far below room temperature (RT). In addition, the ME effect at RT is not large enough to induce a large modulation of electric polarization and magnetization. Therefore, interesting and useful properties via ME coupling, such as large magnetization switching induced by an electric field [2] and control of the non-reciprocal terahertz and microwave response [3,4] were demonstrated only at low temperature.
Here, we report the improvement of ME effects and the ME control of the non-reciprocal microwave response at RT in Y-type BaSrCo2Fe11AlO22 hexaferrite. BaSrCo2Fe11AlO22 was demonstrated to exhibit the ME effect even at RT after appropriate thermal treatment, which improves its electrical insulation property, and the RT mutual control of electric polarization and magnetization at RT has also been successfully realized by the application of magnetic and electric fields [5]. By fabricating highly c-axis oriented ceramics, we significantly improved the magnetic-field induced electric polarization and ME coefficient to ~52 μC/m2 and ~6000 ps/m at RT, respectively. A significant improvement in ME coupling between ferroelectricity and ferromagnetism enables the ME control of the microwave non-reciprocity at RT. These results open up the path for electronic devices controlled by an electric field and are useful for application in communications.
References
[1] T. Kimura, Annual Review of Condensed Matter Physics, 3, 93-110 (2012)
[2] YS. Chai et al., Nature Communications 5, 4208 (2014)
[3] S. Kibayashi et al., Nature Communications 5, 4583 (2014)
[4] Y. Iguchi et al., Nature Communications 8, 15252 (2017)
[5] Sakyo Hirose et al., Applied Physics Letter 104, 022907 (2014)
2:15 PM - *EM02.05.03
MID-CAREER RESEARCHER AWARD TALK: Dynamical Multiferroicity
Nicola Spaldin 1
1 , ETH Zurich, Zurich Switzerland
Show Abstract
An appealing mechanism for inducing multiferroicity in materials is the generation of electric polarization by a spatially varying magnetization that is coupled to the lattice through the spin-orbit interaction. Here we describe the reciprocal effect, in which a time-dependent electric polarization induces magnetization with no prerequisite of existing spin structures. We develop a formalism for this dynamical multiferroic effect for phonons that is feasible for computation from first principles. We show that the phonon Zeeman effect, which is the solid-state equivalent of the well-established vibrational Zeeman effect in molecules, derives straightforwardly from this theory. We further show that a recently observed behavior – the resonant excitation of a magnon by optically driven phonons – is described by the formalism. Finally, we illustrate examples that are not related to lattice dynamics and interpret the excitation of Dzyaloshinskii-Moriya electromagnons and the inverse Faraday effect from the viewpoint of dynamical multiferroicity.
2:45 PM - EM02.05.04
Optical Control of Multiferroicity in BiFeO3 Thin Films
Yu-You Chiu 1 , Yi-De Liou 1 , Ye Cao 3 , Yi-Chun Chen 1 , Sergei Kalinin 3 , Ying-Hao Chu 2 , Jan-Chi Yang 1
1 Department of Physics, National Cheng Kung University, Tainan Taiwan, 3 Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu Taiwan
Show AbstractComplex oxides have caught great attention in the past decades. The interplays of lattice, charge, orbital, and spin degrees of freedom in strongly correlated oxides result in a broad spectrum of intriguing functionalities, such as multiferroicity, high-temperature superconductivity, colossal magneto-resistance and so on, offering tremendous potential for next-generation functional devices. Researchers have been enthusiastically devoted to effective modulation of these intriguing phenomena among complex oxides via external stimuli. Due to the inherent correlations between intrinsic degrees of freedom and external stimuli, the electrical and magnetic fields are the most conventional ways to gain external control on the correlated phenomena. In order to enrich the tunability of functional oxides, the development of additional controlling parameters is on demand along with the existing approaches.
In this work, we demonstrate the optical control of both ferroelectric and antiferromagnetic orders of multiferroic BiFeO3 thin film at room temperature through laser illumination. This approach relies on the intriguing coupling between ferroelectricity and antiferromagnetism in the multiferroic BiFeO3. High quality BiFeO3 thin film samples are grown by pulsed laser deposition, while the optical control features are revealed by a combination of scanning probe microscopy (AFM and PFM modes), Raman spectroscopy, and phase field simulation. With well-tuned laser illumination, the local temperature of illuminated region increases (~ 100 oC), resulting in a significant flexoelectric field at the shedding boundary. This flexoelectric field is then adopted to modulate the local ferroelectricity of BiFeO3 thin film, generating a wide spectrum of tunable domain structures. Due to the fact that BiFeO3 thin film has its ferroelectricity coupled strongly with inherent antiferromagnetism/ferromagnetism, the optical modulation of ferroelectric order gives rise to corresponding alteration of the antiferromagnetism/ferromagnetism as well. Furthermore, we show that the domain conductivity could also be turned on and off via laser illumination. Such demonstrations pave a new pathway to control the intriguing physical properties through the communication between optical stimulus and different order parameters in materials, which leads to new-generation multifunctional devices and applications.
3:30 PM - *EM02.05.05
Imaging, Controlling and Harnessing Non-Collinear Magnetism in Perovskite Oxides
Manuel Bibes 1
1 , CNRS/Thales, Palaiseau France
Show AbstractIn magnetic perovskite oxides ABO3, first-neighbour antiferromagnetic super-exchange interactions usually dominate, but may coexist with other terms such as ferromagnetic double-exchange or Dzyaloshinskii-Moriya interactions at B-O-B and A-O-A bonds. This often produces non-collinear spin configurations leading to weak ferromagnetism or to spatially modulated spin structures. A prototypical non-collinear magnetic oxide is multiferroic BiFeO3 that shows a cycloidal order with a 64 nm period in the bulk. In this talk, I will show how epitaxial strain can be used to tailor the magnetic order of BiFeO3 thin films and present real-space images of the cycloidal structure, as well as its manipulation by an electric field. In a second part I will discuss how magnetic spin texture can influence the Hall response in conducting oxide thin films.
4:00 PM - EM02.05.06
Room Temperature Magnetoelectric Coupling in Amorphous Ferromagnetic Oxide/ BiFeO3 Heterostructures
Humaira Taz 4 , Bhagwati Prasad 1 , Liv Dedon 1 , Jeremy Turcaud 1 , Nikita Gaur 1 , Sahar Saremi 1 , Zuhuang Chen 1 , Charles Henri-Lambert 2 , Ajay Yadav 2 , Tamil Sakthivel 3 , Sudipta Seal 3 , Ramamoorthy Ramesh 1 , Ramki Kalyanaraman 5 6 4
4 Bredesen Center, University of Tennessee, Knoxville, Knoxville, Tennessee, United States, 1 Materials Science and Engineering, University of California, Berkeley, California, United States, 2 Electrical Engineering and Computer Sciences, University of California, Berkeley, California, United States, 3 Materials Science and Engineering, University of Central Florida, Orlando, Florida, United States, 5 Materials Science and Engineering, University of Tennessee, Knoxville, Knoxville, Tennessee, United States, 6 Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, Knoxville, Tennessee, United States
Show AbstractMagnetoelectric (ME) coupling in multiferroic heterostructures at room temperature is a topic of active research due to its potential applications for memory devices. Heterostructures comprising ferromagnetic metallic CoFe layer on top of ferroelectric BiFeO3 (BFO) has recently shown evidence of strong ME coupling at room temperature where the anisotropic magnetoresistance signature of CoFe was modulated by applying an electric field across the BFO [1]. However, these devices suffer from limited switching cycles due to CoFe/BFO interface distortion [1]. This problem can be countered by using an oxide, such as Fe3O4, that has room temperature ferro/ferri-magnetism and high conductivity. However, epitaxial Fe3O4 is difficult to grow on top of BFO due to lattice mismatch, and in the amorphous state Fe3O4 loses the much-desired room temperature ferrimagnetism, becoming superparamagnetic [2].
In this work, we investigate an amorphous Fe-Dy-Tb oxide (FDTO) thin film as the ferromagnetic layer to couple to the underlying BFO. Amorphous FDTO has been shown to possess a combination of low sheet resistance (<200 ohm/sq) and room temperature magnetism with coercivity of around 40 Oe [3, 4]. The FDTO films were deposited by pulsed laser deposition on top of epitaxially grown BFO films at room temperature, in the presence of an in-plane and out-of-plane magnetic field, under varying oxygen pressures ranging from 5e-06 to 2e-06 Torr. The amorphous microstructure was evidenced from grazing incidence x-ray diffraction while x-ray photoelectron spectroscopy confirmed a large degree of surface oxidation. The magnetic measurements demonstrated an increase in the coercive field of FDTO from about 200 Oe on quartz substrate to 1300 Oe on BFO films. The ferroelectric property of BFO was found to be retained for many switching cycles with the FDTO as a top electrode, a major outcome of this research. Various spintronic device structures are being investigated to provide evidence for ME coupling in FDTO/BFO heterostructures. Besides providing an alternative material for the ME coupling in multiferroic devices, FDTO could also be an innovative material for various spintronic applications.
References:
[1] Heron et al. Nature Letters (2014), doi: 10.1038/nature14004
[2] Tang et al. Trans. Nonferrous Met. Soc. China (2006), s249-s252
[3] Malasi et al. Scientific Reports (2015) https://www.nature.com/articles/srep18157
[4] Taz et al. Scientific reports (2016) www.nature.com/articles/srep27869
4:15 PM - EM02.05.07
Magneto-Ionic ON/OFF Switching of Magnetization in FeOx/Fe Nanostructures
Jonas Zehner 1 , Kenny Duschek 1 , Nicolas Perez 1 , Andreas Petr 1 , Rudolf Schafer 1 , Kornelius Nielsch 1 , Karin Leistner 1
1 , IFW Dresden, Dresden Germany
Show AbstractVoltage - induced ion migration and electrochemical oxidation/reduction was recently discovered as a novel route for low-power voltage-control of magnetism in oxide/metal films [1,2]. The term magneto-ionic has been introduced to distinguish it from other magneto-electric effects in multiferroics, magnetic semiconductors or by capacitive charging [1,3]. A key advantage of magneto-ionic effects, especially in comparison to capacitive electronic charging of metal surfaces, is that non-volatile voltage-programming of magnetic properties becomes possible [2,3]. In all-solid magneto-ionic architectures significant effects are obtained at elevated temperatures, when thermal activation facilitates ion migration.
We present large voltage-induced magnetic changes within several nanometers of FeOx/Fe films at room temperature. The voltage is applied via a liquid alkaline electrolyte [4] (KOH or LiOH solution), which, in comparison to solid oxide gate barrier layers, yields an enhanced electric field and a higher ion mobility at the electrode surface. The magnetic changes are proven by two independent methods: in situ anomalous Hall effect and in situ ferromagnetic resonance measurements. Nearly complete and reversible voltage-induced ON/OFF switching of magnetization (up to 90 %) is observed in granular FeOx/Fe thin films for a voltage change of 1 V. The combination of such a tunable Fe layer with an underlying layer exhibiting perpendicular magnetic anisotropy like in our case L10-FePt (001) allows the additional achievement of large magneto-ionic changes of the effective anisotropy [4]. An in situ Kerr microscope set-up has been developed that resolves for the first time magnetic domains through a liquid alkaline electrolyte. Thereby, for the first time, the study of the local impact of electrochemical reactions on the magnetic domain characteristics becomes possible for solid/liquid magneto-ionic systems.
[1] C. Song, B. Cui, F. Li, X. Zhou, F. Pan: Recent progress in voltage control of magnetism: Materials, mechanisms, and performance, Progress in Materials Science 87, 33-82, 2017
DOI: 10.1016/j.pmatsci.2017.02.002
[2] K. Leistner, J. Wunderwald, N. Lange, S. Oswald, M. Richter, H. Zhang, L. Schultz, S. Fähler: Electric-field control of magnetism by reversible surface reduction and oxidation reactions, Physical Review B 87, 224411, 2013
DOI: 10.1103/PhysRevB.87.224411
[3] U. Bauer, L. Yao, A. J. Tan, P. Agrawal, S. Emori, H. L. Tuller, S. van Dijken, G.S.D. Beach: Magneto-ionic control of interfacial magnetism, Nature Materials 14, 174-181, 2015
DOI: 10.1038/nmat4134
[4] K. Duschek, D. Pohl, S. Fähler, K. Nielsch, K. Leistner: Research Update: Magnetoionic control of magnetization and anisotropy in layered oxide/metal heterostructures, APL Materials 4, 032301, 2016
DOI: 10.1063/1.4942636
4:30 PM - EM02.05.08
Origin of the Photo-Induced Current of Strongly Correlated YMnO3 Ferroelectric Epitaxial Films
Norifumi Fujimura 1 , Kohei Miura 1 , Takeshi Yoshimura 1 , Daisuke Kiriya 1 , Atsushi Ashida 1
1 Physics and Electronics, Osaka Prefecture University, Sakai, Osaka, Japan
Show AbstractWe have studied the photo-induced carrier generation and the carrier emission resulted in a photo-induced current using strongly correlated YMnO3 ferroelectric thin films. Unipolar material YMnO3 are suitable for studying the effect of the ferroelectric polarization on the photo-induced current. The clear relationship between the direction of the polarization and the photo-induced current was recognized using (0001) YMnO3 epitaxial films. The current switching corresponding to the polarization switching is also observed under the illumination of white light. To study the origin of the photo-induced current originated from the photo-induced carrier generation, the light energy dependence of the photo-induced current was investigated. The small peak at 1.75 eV and broad peak at around 2.5 eV are observed at room temperature. The peak at 1.75 eV corresponds to the optical absorption at 1.7 eV that generated by the electron transition between Mn 3d (xy,x2-y2)(e2g state)/O 2p hybridized band and upper Mn 3d (3z2-r2)(a1g state) orbital [1]. The broad peak of photo-induced current corresponds to the broad photoluminescence excitation spectrum at around 2.5 eV, which is never observed in absorption measurement but reported as the hidden optical channel. The origin of photo-induced current of YMnO3 is discussed associated with the carrier generation and the emission process.
[1]M. Nakayama et al., Appl. Phys. Express, 7, 023002 (2014)
4:45 PM - EM02.05.09
Nanoscale Cross-Sectional Imaging of Functional Properties in Multiferroic Thin Films
James Steffes 1 , Ramamoorthy Ramesh 2 , Bryan Huey 1
1 , University of Connecticut, Storrs Mansfield, Connecticut, United States, 2 , University of California, Berkeley, California, United States
Show AbstractAtomic force microscopy (AFM) is employed to map functional properties through the thickness of multiferroic thin films. High-resolution piezoresponse force microscopy (PFM) and conductive AFM (CAFM) data reveals ferroelectric and multiferroic properties in Pb(Zr0.2Ti0.8)O3 and BiFeO3 films, as well as BaTiO3/SrTiO3 superlattices. This uniquely allows structure-property relationships to be directly assessed as a function of thickness between one and several hundred nanometers, including the ferroelectric coercive field, polarization reversal dynamics, and conductivity of multiferroic domain walls. Switchable ferroelectricity and coercive field scaling that follows Kay-Dunn behavior are demonstrated to less than 5 nm film thickness in BiFeO3. Such cross-sectional AFM also allows for imaging and analysis of otherwise inaccessible buried features, including charged domain walls, superlattice layers, and sub-surface defects. Along with complementary transmission electron microscopy (TEM) analysis, this work provides new insights into the relationship between strain and ferroelectricity in heteroepitaxial multiferroics and multilayer structures.
EM02.06: Poster Session II: Multiferroics
Session Chairs
Xianfeng Liang
Guolong Tan
Wednesday AM, November 29, 2017
Hynes, Level 1, Hall B
8:00 PM - EM02.06.01
Observation of Re-Entrant Spin Reorientation and Magnetocaloric Effect in TbFe1-xMnxO3 Oxide
Yifei Fang 1 , Fei Chen 1 , Jinyan Ning 1 , Jincang Zhang 1
1 , Materials Genome Institute, Shanghai University, Shanghai, Shanghai, China
Show AbstractWe report a spin reorientation from Γ4(Gx, Ay, Fz) to Γ1(Ax, Gy, Cz) magnetic configuration near room temperature and a re-entrant transition from Γ1(Ax, Gy, Cz) to Γ4(Gx, Ay, Fz)at low temperature in TbFe1-xMnxO3 single crystals by performing both magnetization and neutron diffraction measurements. The Γ4-Γ1 spin reorientation temperature can be enhanced to room temperature when x is around 0.5~0.6. These new transitions are distinct from the well-known Γ4-Γ2 transition observed in TbFeO3, and the sinusoidal antiferromagnetism to complex spiral magnetism transition observed in multiferroic TbMnO3. We further study the evolution of magnetic entropy change (-△S) versus Mn concentration to reveal the mechanism of the re-entrant spin reorientation behavior and the complex magnetic phase at low temperature. The variation of -△S between a and c axes indicates the significant change of magnetocrystalline anisotropy energy in the TbFe1-xMnxO3 system. Furthermore, as Jahn-Teller inactive Fe3+ ions coexist with Jahn-Teller active Mn3+ ions, various anisotropy interactions, compete with each other, giving rise to a rich magnetic phase diagram. The large magnetocaloric effect reveals that the studied material could be a potential magnetic refrigerant. These findings expand our knowledge of spin reorientation phenomena and offer the alternative realization of spin-switching devices at room temperature in the rare-earth orthoferrites.
8:00 PM - EM02.06.02
Magnetic Structure and Spin Wave Excitations in the Multiferroic Magnetic Metal Organic Framework (CD3)2ND2[Mn(DCO2)3]
Helen Walker 1 , Helen Duncan 2 3 , Duc Le 1 , David Keen 1 , David Voneshen 1 , Anthony Phillips 3
1 ISIS Neutron and Muon Source, Rutherford Appleton Laboratory, Didcot United Kingdom, 2 Centre for Science at Extreme Conditions, University of Edinburgh, Edinburgh United Kingdom, 3 School of Physics and Astronomy, Queen Mary University of London, London United Kingdom
Show AbstractFor the past fifteen years there has been considerable interest in magnetoelectric multiferroics, both from the fundamental viewpoint and driven by the desire to create functional systems for modern technologies [1]. The search for optimal systems has revealed that traditional magnetic compounds are currently limited in providing the flexibility and complex functionality required. This has resulted in attention now being turned to dense metal organic frameworks (MOFs), which present a versatile platform for the realization of complex magnets due to the high tailorability and tunability arising from their discrete molecular building-block nature [2]. However, the magnetic properties of such materials depend on their precise magnetic interactions, which are often poorly understood. In particular, while bulk magnetometry is routinely performed on newly reported materials, magnetic diffraction measurements are far less often reported, and magnetic spectroscopy is rarer still. If we are to develop multiferroic MOFs for future applications it is vital that we rectify this situation, and obtain a greater understanding of the origin of their properties.
The dimethylammonium transition metal formates (DMMF) are one such family of magnetic MOFs displaying intriguing properties. These materials may exhibit both electric and magnetic ordering, and their properties can be tuned by preparing solid solutions with substitution of either the metal or the organic cation. Understanding the origins of these materials' electric and magnetic properties would allow this tunability to be exploited to design materials with targeted functionalities.
DMMnF is the first reported perovskite metal-organic multiferroic [3]. It is a Type-I single phase multiferroic, since the magnetic ordering comes from the interactions of the Mn2+ ions mediated by the formate linkers, while the electric ordering comes from rotation of the (CH3)2NH2+ ions within the framework. A Curie-Weiss fit to the inverse magnetic susceptibility gives an effective paramagnetic moment of 5.94μB consistent with that expected for S = 5/2 Mn2+ and a negative Curie-Weiss constant of -16.3 K, confirming the presence of antiferromagnetic interactions. Based on molecular field theory, this temperature can be converted into an estimate for the exchange interaction of -0.0397 meV.
I will present the results of our powder elastic and inelastic neutron scattering study of perdeuterated dimethylammonium manganese formate. Results will be compared with simulations for different exchange interaction models and with literature magnetometry data. While powder inelastic neutron scattering has proven to be a highly effective technique to probe magnetism in the inorganic perovskites; I will show that it is equally effective at revealing the behaviour of their metal-organic analogues.
[1] J. Scott, Nat. Mat., 6, 256 (2007).
[2] M. Kurmoo, Chem. Soc. Rev., 38, 1353 (2009).
[3] P. Jain et al., J. Am. Chem. Soc., 131, 13625, (2009)
8:00 PM - EM02.06.03
High-Pressure Synthesis and Magnetic and Dielectric Properties of B-Site Ordered and Disordered LiNbO3-Type Oxide Mn(Fe1/2Ta1/2)O3 and Mn(Fe1/2Nb1/2)O3
Akihisa Aimi 1 , Daisuke Mori 2 , Yoshiyuki Inaguma 3 , Kenjiro Fujimoto 1
1 , Tokyo University of Science, Noda-shi Japan, 2 , Mie University, Tsu-shi, Mie, Japan, 3 , Gakushuin University, Toshima-ku, Tokyo, Japan
Show AbstractPolar LiNbO3-type oxides containing magnetic transition metal cations are promising multiferroic materials. For example, LiNbO3-type MnMO3 (M = Ti, Sn) exhibits the correlation between magnetic and dielectric properties1. Recently, LiNbO3-type oxide with multiple B-site cations Mn(Fe1/2M1/2)O3 (M = Nb, Ta) have been synthesized and its magnetic properties have been studied2. The magnetic phases of both the compounds are weak-ferromagnetic(WFM) around 200 K, but show different behaviors at low temperature. The magnetic phases for Mn(Fe1/2Ta1/2)O3 and Mn(Fe1/2Nb1/2)O3 are anti-ferromagnetic(AFM) and frustrated AFM, respectively. In this study, we successfully synthesized Mn(Fe1/2Ta1/2)O3 with rock-salt-type ordering of the Fe and Ta and studied the relationship between crystal structures and magnetic properties.
Mn(Fe1/2M1/2)O3 (M = Nb, Ta) were synthesized by high-pressure method. Stoichiometric amounts of MnO, Fe2O3 and M2O5 (M = Nb, Ta) were ground and then heated for 1073 K - 1473 K at 7.5 GPa. Phase identifications were performed by the powder X-ray diffraction (XRD) method. Structure refinements were performed by Rietveld method for synchrotron powder XRD data using RIETAN-FP software. Magnetic properties were measured in the temperature range of 5 K – 300 K in applied magnetic field up to 10 kOe. Dielectric properties were measured in the temperature range of 10 K - 300 K.
Single phase of LiNbO3-type (space group R3c) Mn(Fe1/2Nb1/2)O3 was synthesized at 1473 K under 7.5 GPa. In contrast, structure of Mn(Fe1/2Ta1/2)O3 varied with synthesized temperature. The R3c phase crystallized at 1173 K and 1473 K, and R3 phase crystallized at 1273 K under a pressure of 7.5 GPa. The structure refinement of these samples revealed that in R3 phase, Fe and Ta ordered with rock-salt-type arrangement in B-site of LiNbO3-type structure, and degree of ordering is about 74 %.
Both of the Mn(Fe1/2Nb1/2)O3 and R3c Mn(Fe1/2Ta1/2)O3 exhibited WFM transition around 160 K and AFM transition around 100 K. The magnetic phase transition sequence of these compounds is similar to Morin transition of hematite3. R3 Mn(Fe1/2Ta1/2)O3 exhibit AFM transition around 240 K, indicating that B-site cation disordering is responsible to the WFM interaction in Mn(Fe1/2M1/2)O3 (M = Nb, Ta) system.
Broad peaks were observed in dielectric loss at AFM transition temperature for R3c Mn(Fe1/2M1/2)O3, implying existence of correlation between magnetic phase and dielectric properties.
Acknowledgment
The synchrotron XRD experiment was conducted at BL02B2 of SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (JASRI) (Proposal No. 2013A1697, 2012B1678).
This work was supported by JSPS KAKENHI Grant Numbers 21360325, 24360275 and 15H04128.
Reference
[1] Aimi, A. et al., Inorg. Chem. 2011, 50 (13), 6392-6398. [2] Li, M. R. et al., Angew. Chem. Int. Ed. 2013, 52 (32), 8406-8410. [3] Morin, F. J., Phys. Rev. 1950, 78 (6), 819-820.
8:00 PM - EM02.06.04
Study of Multiferroic Properties of BaTiO3 Nanocrystals by Dynamic Piezoresponse Force Microscopy (D-PFM) and Vibrating Sample Magnetometer (VSM)
Tommaso Costanzo 1 , Gabriel Caruntu 2
1 Science of Advanced Materials, Central Michigan University, Mount Pleasant, Michigan, United States, 2 Department of Chemistry and Biochemistry, Central Michigan University, Mount Pleasant, Michigan, United States
Show AbstractMultiferroic materials are characterized by the coexistence of two or more ferroic properties, such as ferroelectricity, ferromagnetism and ferroelasticity. Exploiting the coupling between various ferroic order parameters in multiferroics holds great promise for the development of high performance memories, energy harvesting/storage and sensing devices. As nanostructuring is an efficient way to improve the performance characteristics of materials, the strict control over size and shape of nanoparticles is key for the integration of nanoscale multiferroics into functional devices. Here, we report on the characterization of single crystalline, monodiperse BaFe1-xTixO3 colloidal cube-like nanocrystals (with x between 0 and 0.6) with sizes varying from 15 nm to 65 nm. The VSM measurements have shown that the magnetic moment increases up to a 4% of Fe content, which however, starts decreasing when the concentration increases past 4% due to the antiferromagnetic coupling of nearest Fe3+ ions.1 The analysis of PFM data revealed a strong dependency of the tip response to the size of the nanocrystals. Specifically, when the edge length of the nanocubes increases from 15 to 25 nm, the hysteresis loop becomes sharper (e.g. switching in a narrow range of voltages) and showing higher remanent responses, indicative of better ferroelectric properties. In contrast, in nanocrystals with sizes of 45 and 65 nm the PFM response shows anomalous hysteresis loops. These results suggest that multiferroism can be achieved only in BaFe1-xTixO3 (with x between 0 and 0.2) nanocrystals with size below 45 nm. These findings unambiguously demonstrate that the control of the nanocrystals size is crucial for the development of room temperature multiferroic BaTiO3.
1 L. Yang, H. Qiu, L. Pan, Z. Guo, M. Xu, J. Yin and X. Zhao, J. Magn. Magn. Mater., 2014, 350, 1–5.
8:00 PM - EM02.06.05
Ordered and Disordered Sr2CrReO6—Structures and Properties
Miguel Angel Alario-Franco 1 , Rebecca Smaha 1 , Paola Ramos-Alvarez 1 , Elena Solana-Madruga 1 , Esteban Urones-Garrrote 1 , Regino Saez-Puche 1 , Susana Garcia-Martin 1
1 , Univ Complutense, Madrid Spain
Show AbstractWe are revisiting here the synthesis and characterization of both the disordered and the ordered phases of the double perovskite Sr2CrReO6. The structural differences between these two phases are elucidated by X-ray diffraction and transmission electron microscopy. These two phases show significant differences in their magnetic properties related to the different oxidation states of Cr and Re: Ordered Sr2ReCrO6 is a canted antiferromagnet with a Tn of ~300 K, while disordered Sr2ReO6 is also antiferromagnetic with an ordering temperature well above room T. We will discuss these results within the context of magnetic double perovskites
8:00 PM - EM02.06.06
Multiple Anomalies in the Temperature Evolution of SmFeO3 Single Crystals
Mads Weber 2 1 3 , Mael Guennou 1 , Michael Carpenter 4 , Wei Ren 5 , Brahim Dkhil 6 , Jens Kreisel 1 3
2 , ETH Zürich, Zürich Switzerland, 1 , Luxembourg Institute of Science and Technology, Belvaux Luxembourg, 3 , University of Luxembourg, Belvaux Luxembourg, 4 , University of Cambridge, Cambridge United Kingdom, 5 Department of Physics, Shanghai University, Shanghai China, 6 , Ecole Centrale-Supélec, Chatenay-Malabry France
Show AbstractSamarium ferrite SmFeO3 is a member of the family of rare-earth orthoferrites RFeO3, which have been under investigation for some time for their rich magnetic properties including non-collinear magnetism and spin reorientation transitions [1]. Recently, it has been shown that the interplay between the iron and rare-earth magnetic sublattices may break inversion symmetry – even with collinear magnetic orders, giving rise to polar phases, or in other words type-II multiferroics [2]. This is notably expected to happen in SmFeO3, but, in spite of considerable experimental attention and claims of ferroelectric properties at low or even ambient temperatures, its polar character remains to date controversial [3,4].
In this work, we report temperature studies of SmFeO3 single crystals by a variety of experimental techniques (Raman spectroscopy, resonance ultrasound spectroscopy – RUS, birefringence measurements) over a broad temperature range from liquid helium to 800 K. We discuss the sensitivity and complementarity of those techniques as probes for the different transitions and discuss the possible scenarii for the low-temperature behavior of SmFeO3 in the light of the various anomalies observed.
[1] E. Bousquet and A. Cano, J. Phys.: Cond. Matter, 28, 123001 (2016).
[2] H.-J. Zhao et al., Nature Comm., 8, 14025 (2017).
[3] J.-H. Lee et al., Phys. Rev. Letters, 107, 117201 (2011).
[4] C.-Y. Kuo et al., Phys. Rev. Letters, 113, 217203 (2014).
8:00 PM - EM02.06.07
Synthesis and Optimization of Nickel Ferrite (NiFe2O4) Nanoparticles Using Hydrothermal Method at Different Parameters
Mukesh Kumari 1 , Mukesh Chander 1
1 , IIT Delhi, New Delhi India
Show AbstractNickel ferrite (NiFe2O4) nanoparticles have promising electrical and magnetic properties and have many applications. Magnetic nanoparticles can be synthesized by various techniques including co-precipitation, hydrothermal synthesis, thermal decomposition, microemulsion and sol-gel, etc.In this paper, we have been synthesized NiFe2O4 nanoparticles by hydrothermal method to studied the effect of variation of volume of sodium hydroxide (NaOH) solution and synthesis temperature on the structural, morphological and magnetic properties of NiFe2O4 nanoparticles. We have been synthesized NiFe2O4 nanoparticles by taking a solution of nickel nitrate and ferric nitrate in 1:2 molar ratios mixed with different volume of 3M NaOH solution at 160°C temperature. Further, NiFe2O4 nanoparticles were prepared at fixed 3M NaOH volume by varying temperatures 140°C, 160°C, 180°C, 200°C and 220°C. The structural optimization of prepared samples was done by X-ray diffraction (XRD) and Raman spectroscopy. Scanning electron microscopy (SEM) technique was used for morphological study and magnetic properties were analyzed by physical property measurement system (PPMS) characterization technique. XRD and Raman analysis confirmed the single phase formation of NiFe2O4 nanoparticles except for sample grown at temperature 140°C where some undesirable peaks have been seen. Crystallite size of nanoparticles calculated by scherrer’s formula was found to lie in range 35 to 45nm. SEM images revealed the formation of nano-octahedrons. Study of magnetic properties at room temperature shows that the saturation magnetization (Ms) increases with volume of NaOH solution in range 37 to 56 emu/gm. Coercivity (Hc) decreases from 88 to30 Oe with rise in volume of 3M NaOH solution and remains constant onwards. There is no regular trend was found in the magnetic properties of samples prepared with the variation of temperature. Sample prepared at temperature 160°C has highest Hc .
Symposium Organizers
Nian Sun, Northeastern University
Franz Faupel, Kiel University
Cewen Nan, Tsinghua University
Ramamoorthy Ramesh, University of California, Berkeley
EM02.07: Magnetoelectrics III
Session Chairs
Jiamian Hu
Yayoi Takamura
Wednesday AM, November 29, 2017
Hynes, Level 1, Room 107
8:00 AM - EM02.07.01
Probing the Emergence of Polarization in Improper Ferroelectric Thin Films During Growth
Johanna Nordlander 1 , Marta Rossell 2 , Nives Bonačić 1 , Gabriele De Luca 1 , Morgan Trassin 1 , Manfred Fiebig 1
1 Department of Materials, ETH Zurich, Zürich Switzerland, 2 , Electron Microscopy Center, Empa, Swiss Federal Laboratories for Materials Science and Technology, Dübendorf Switzerland
Show AbstractImproper ferroelectrics are materials whose ferroelectricity is driven by a non-polar order parameter. This type of ferroelectricity can lead to exotic properties that do not exist in standard ferroelectrics. In the case of bulk hexagonal manganites, the structural trimerization results in a topologically protected vortex domain structure. Due to their potential for complex functional properties, there has been a revival in the growth of hexagonal manganite thin films. Only recently, there were demonstrations of thin films showing bulk-like properties, and domain vortices were also reported in thin epitaxial layers. Here we demonstrate the growth of highly oriented, epitaxial hexagonal YMnO3 thin films using pulsed laser deposition. We use in-situ optical second harmonic generation (SHG) to non-invasively probe the ferroic state of hexagonal manganite YMnO3 thin films. We monitor, in real time, the emergence of the polar state in hexagonal YMnO3 thin films during the pulsed laser deposition process. With the simultaneous use of SHG and reflection high-energy electron diffraction (RHEED), the emerging polarization of YMnO3 is resolved with mono-layer accuracy. The characteristic improper ferroelectric domain pattern in the ultrathin YMnO3 films is investigated using scanning transmission electron microscopy. This work provides new insights in the early stage of the ferroelectricity and domain state in YMnO3 – determined by topology rather than electrostatics. Ultimately, we show how the appearance of polarization in this improper ferroelectric fundamentally differs from that of conventional ferroelectrics, such as BaTiO3.
8:15 AM - EM02.07.02
The Effect of Seed Layers on the Perpendicular Magnetic Anisotropy in Tetragonal D022 Mn3Ge Epitaxial Films
Yuyi Wei 1 , Mingmin Zhu 1 2 , Gregory Stephen 3 , Ming Liu 2 , Wei Ren 2 , Don Heiman 3 , Nian Sun 1
1 Electrical and Computer Engineering Department, Northeastern University, Boston, Massachusetts, United States, 2 Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, Xi’an Jiaotong University, Xi'an, Shaanxi, China, 3 Department of Physics, Northeastern University, Boston, Massachusetts, United States
Show AbstractThe increasing research interest in the spin transfer torque magnetic random access memory (STT-MRAM) has required a perpendicularly magnetized thin film with low saturation magnetization, low Gilbert damping constant, high uniaxial anisotropy constant and high spin polarization being used in magnetic tunnel junctions(MTJs). Tetragonally distorted Heusler compounds meet these criteria and Mn3Ge is one of the attractive Heusler systems for exploring its potential application in the STT-MRAM devices. However, due to the tetragonal lattice distortion the strong perpendicular magnetic anisotropy(PMA) only occurs in the D022 phase of Mn3Ge, with the easy axis along the c direction. Therefore, the epitaxial growth of D022-Mn3Ge with (001) orientation is very critical for obtaining strong PMA, which can be significantly affected by the seed layers between Mn3Ge film and the substrates.
A systematic study of sputtered Mn3Ge films on MgO substrates with various seed layers, including Cr(40nm), Cr(20nm)/Pt(10nm) and Fe(2nm)/Pt(10nm), has been investigated. The Mn3Ge (004) peak, a signature of the film crystallization in the tetragonal D022 phase, can be observed in the XRD patterns of all films. The strongest peak is observed in the Mn3Ge film with Fe/Pt as the seed layer, in which the Mn3Ge (002) peak also occurs with Pt thickness optimization, showing the best c-axis crystallization. The magnetic anisotropy properties of all films were performed by the SQUID-VSM system, shown in Figure (b-d). The lowest coercivity of about 1T is achieved in the Mn3Ge film with Fe(2)/Pt(15) as the buffer layer, which also shows lower saturation magnetization of 98.5 emu/cm3. These dependences of crystallization and magnetic properties on the seed layers can make the tetragonal Mn3Ge thin films as a candidate for optimal STT applications.
Key Words: perpendicular magnetic anisotropy, Mn3Ge, epitaxial film
8:30 AM - *EM02.07.03
Strain and Charge-Mediated Magnetoelectric Effects in Complex Oxide Heterostructures
Rajesh Chopdekar 1 , Yayoi Takamura 1
1 , University of California, Davis, Davis, California, United States
Show AbstractAn intense research effort towards the study of room-temperature magnetoelectric interactions in artificial multiferroic systems is underway to circumvent the limitations found in single-phase multiferroic materials. Epitaxial manganite heterostructures offer a rich combination of functional properties at or near room temperature with the ability to tune such properties through lattice, charge, spin, and orbital degrees of freedom.1 Recent work has shown that a (011)-oriented relaxor ferroelectric substrate (e.g. Pb(Mg,Nb,Ti)O3) in combination with a manganite film (e.g. (La,Sr)MnO3) can show significant changes in magnetization upon poling of the ferroelectric substrate, due to strain-driven changes in both eg electron itinerancy and the magnetoelastic anisotropy energy landscape.2,3 Both strain magnitude and film-interface charge can significantly affect resistive and magnetic properties of this model manganite-titanate heterostructure. For film thicknesses ranging from 4-40 nm, a change in the orientation of the ferroelectric domains from out-of-plane to in-plane results in a large, anisotropic, and nonvolatile change in tensile strain by 0.2% as well as a transition from large twofold to weak fourfold magnetic anisotropy. The region of the film near the manganite-titanate interface is susceptible to electrostatic doping, and by varying the film thickness, the relative contribution of strain- and charge-based magnetoelectric interactions can be modulated. Electrostatic doping set by the polarity of the out-of-plane ferroelectric domains results in a 6% nonvolatile change in resistivity at room temperature for a 5 nm thick film. At this film thickness, photoinjection of carriers induced by a 405 nm laser diode at 50 mW/cm2 effectively screens the ferroelectric interface charge and modulates the electrostatic doping effect by 30%, whereas a negligible change is observed in the strain-modulated resistivity of a 15 nm thick film. These results demonstrate that artificial multiferroic heterostructures formed from complex oxides can show large and robust changes in resistive and magnetic properties at room temperature through strain- and charge-based magnetoelectric effects with tunability using applied magnetic and electric fields as well as visible-light illumination.
1. Vaz et al., J. Phys.: Condens. Matter 27, 123001 (2015)
2. Heidler, Chopdekar et al., Phys. Rev. B 91, 024406 (2015)
3. Chopdekar, Takamura et al., Sci. Rep. 6, 27501 (2016)
9:00 AM - EM02.07.04
Fully Suspended Thin Film Magnetoelectric Heterostructures as Micro-Beam Resonators for High Sensitivity Magnetic Sensing in Large Background Magnetic Fields
Steven Bennett 1 , Margo Staruch 1 , Jeffrey Baldwin 1 , Bernard Matis 1 , Konrad Bussmann 1 , William Zappone 2 , Ronald LaComb 2 , Peter Finkel 1
1 , The U.S. Naval Research Laboratory, Washington, District of Columbia, United States, 2 , Naval Undersea Warfare Center (NUWC), Middletown, Rhode Island, United States
Show AbstractIt’s becoming more and more crucial to develop cryogen-free, chip based, high sensitivity magnetic sensors which can operate in large background magnetic fields. This new generation of sensors must perform at very low power consumption, ruling out most of our current-hungry technologies (i.e. search-coil, Hall effect, flux gate, fiber optic, superconducting quantum interference device (SQUID) etc…). Recent advances in our understanding of strain sensitivity of multiferroic magnetoelctric (ME) heterostructures have opened the door to novel micron-scale magnetic field tunable resonator devices [1,2,3]. Here we show how a high moment magnetostrictive metal (FeCo/FeCo(V,B))) can be grown in-situ on a piezoelectric (AlN/PZT) micro-beam with coupled heterostructural strain. By tuning deposition and processing conditions for stress mitigation we have been able to fully remove the substrate material and create a completely suspended double clamped thin film ME micro-beam heterostructure. The sensing concept is based on measuring a magnetic field change using the first harmonic mode resonance frequency shift due to the field induced magnetoelastic effect which is proportional to the applied magnetic field [3]. We reveal here the signal captured by the piezoelectric layer following a non-saturating trend out to large magnetic fields (>1500G); making it an ideal candidate for the close to zero power high relative sensitivity detection of a small time variable magnetic field, hidden in a large background magnetic field.
[1] E. Lage, et. Al., Nature Materials 11 (2012)
[2] Y. Wang, et. Al., Materials Today 17 (2014)
[3] S.P. Bennett, et. Al., Sci. Rep. 6 (2016)
[3] M. Staruch, et. Al., Appl. Phys. Lett. 107 (2015)
9:15 AM - *EM02.07.05
Flexible Multiferroic Bulk Heterojunction with Giant Magnetoelectric Coupling via van der Waals Heteroepitaxy
Ying-Hao Chu 1
1 , National Chiao Tung University, Hsinchu Taiwan
Show AbstractMagnetoelectric nanocomposites have been a topic of intense research due to their profound potential in the applications of magnetic sensors. In spite of significant progress made in the growth of high-quality nanocomposites via thin film deposition, the substrate clamping effect still remains a major hurdle in the realization of ultimate magnetoelectric coupling. To overcome this obstacle, an alternative strategy of fabricating self-assembled ferroelectric-ferrimagnetic bulk heterojunction on flexible muscovite via the van der Waals epitaxy is adopted. We investigated the magnetoelectric coupling in self-assembled BiFeO3 (BFO)-CoFe2O4 (CFO) bulk heteroepitaxy on muscovite wherein BFO nanopillars embedded in CFO matrix exhibit an incoherent growth with minimal substrate clamping due to the weak interaction between the substrate and bulk heterojunction. The magnetic and electrical characterizations highlight the improvement in magnetoelectric coupling of BFO-CFO bulk heterojunction. A large magnetoelectric coupling coefficient of 74 mV/cmOe desirable for the applications of highly sensitive magnetic sensor is achieved. Moreover, the fabricated heteroepitaxy on muscovite offers the additional advantage of being flexible. Therefore, this study delivers a viable route of fabricating highly-sensitive and yet flexible magnetoelectric sensors that are robust against extreme conditions with optimized performance.
9:45 AM - EM02.07.06
Integrated Voltage Tunable RF Magnetoelectric Inductors
Huaihao Chen 1 , Xinjun Wang 1 , Xiaoling Shi 2 , Yuan Gao 2 , Nian Sun 1
1 , Northeastern University, Boston, Massachusetts, United States, 2 , Winchester Technology, Winchester, Massachusetts, United States
Show AbstractAbstract—At present, most designs of integrated inductors in radio frequency integrated circuits (RFIC) consist of a spiral coil without magnetic material, leading to quite limit values of 1-10 nH in terms of inductances, while quality factors are usually below 10. Moreover, these inductors typically have low areal density, resulting in large inductor area and strong electromagnetic interference that limit the RFIC performance. The integrated inductors with magnetic cores show a great potential for RF application, which can promote the inductance and quality factor with smaller size. However, due to the intrinsic magnetic losses and the fundamental tradeoffs of the magnetic materials, the usefulness of the magnetic inductor is severely constrained at GHz frequency range.
In our work, a novel inductor based on solenoid structure with FeGaB/Al2O3 multilayer as magnetic core is designed. A flat inductance of 0.68 nH and a peak quality factor of ~23 have been achieved in a wide operation frequency range 0.5-2 GHz. Magnetic field tunablility of >40% is achieved, under a magnetic field changing from 0 Oe to 300 Oe. Then, voltage tunable magnetoelectric inductors are realized by attaching PMN-PT to the backside of inductor. A tunability of >200% can be achieved while an electric field ranging from 0 kV/cm to 10 kV/cm is applied. Such high quality factor and high inductance density together with giant electrical tunability greatly improved the integration level and performance of radio frequency integrated circuits, while reducing their power consumption and cost.
Keywords—magnetic solenoid inductor, RF inductor, high tunability, high Q, FeGaB multilayer film
10:30 AM - *EM02.07.07
A Flexible, High-Performance Magnetoelectric Heterostructure of (001) Oriented Pb(Zr0.52Ti0.48)O3 Film Grown on Ni Foil
Susan Trolier-McKinstry 1 , Jungho Ryu 2 , Hong Goo Yeo 1 , Haribabu Palneedi 2
1 , The Pennsylvania State University, University Park, Pennsylvania, United States, 2 Functional Ceramics Group, Korea Institute of Materials Science, Changwon Korea (the Republic of)
Show AbstractMultifunctional magnetoelectric (ME) composites consisting of piezoelectric films deposited on magnetostrictive flexible metal foil substrates have potential applications in sensors, energy harvesters, and wearable electronics. In this study, a flexible ME heterostructure of PZT/Ni was fabricated by depositing a (001) oriented Pb(Zr0.52Ti0.48)O3 (PZT) film on a thin, flexible Ni foil buffered with LaNiO3/HfO2. By tailoring the domain state of the PZT film to be predominantly c-domain, excellent ferroelectric properties together with a strong ME coupling of 3.2 V/cmOe were realized. The high performance of the PZT/Ni composite is attributed to the strong texturing of the PZT film under compressive stress and the film on foil architecture of the composite. The large ME output obtained herein is the best reported yet for ME film composites based on either PZT/Ni or textured PZT films deposited on other magnetostrictive substrates.
11:00 AM - EM02.07.08
Strain Control of Magnetic Spin Reconstructions at the (111)-Oriented La0.7Sr0.3MnO3/LaFeO3 Interface
Ingrid Hallsteinsen 1 2 , Kristoffer Kjaernes 1 , Alexander Grutter 3 , Dustin Gilbert 3 , Torstein Bolstad 1 , Magnus Nord 1 , Randi Holmestad 1 , Brian Kirby 3 , Elke Arenholz 2 , Thomas Tybell 1
1 , Norwegian University of Science and Technology, Trondheim Norway, 2 Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 3 Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland, United States
Show AbstractInterfacial magnetism in epitaxial oxide heterostructures can be controlled by strain, for example by modifying structural reconstructions at oxide interfaces resulting in emerging magnetic phases at the interface. As a model system we investigate epitaxial heterostructures consisting of antiferromagnetic LaFeO3 (LFO) and ferromagnetic La0.7Sr0.3MnO3 (LSMO) grown in the (111)-interface orientation, a system showing no charge transfer. Epitaxial single crystalline thin films are synthesized by pulsed laser deposition, and the magnetic and atomic structure is characterized using a combination of soft x-ray spectroscopy, neutron reflectometry and electron microscopy. For LSMO/LFO synthesized on SrTiO3 an induced ferromagnetic moment, ~1.6-2.0 µB/Fe –atom, is found antiparallel to the ferromagnetic moments of LSMO for LFO thicknesses less than 4nm (1). The effect spans 2-4 monolayers into the LFO from the LSMO interface, while the rest of the LFO is antiferromagnetically ordered with an out-of-plane component of the antiferromagnetic axis. The depth of the magnetic reconstruction coincides with a region of structural interface reconstructions due to the different octahedral tilt pattern of LFO and LSMO. By relying on substrates with different symmetry, e.g. rhombohedral and orthorhombic, we show that it is possible to control the magnetic spin texture at the interface, albeit all LSMO/LFO interfaces investigated exhibit a magnetic interface reconstruction of the Fe magnetic order. Hence the data strongly points towards the possibility to rely on structural reconstructions to induce and control interface magnetism by tuning the interface octahedral structure based on strain.
1 I. Hallsteinsen, M. Moreau, A. Grutter, M. Nord, P. E. Vullum, D. A. Gilbert, T. Bolstad, J. K. Grepstad, R. Holmestad, S. M. Selbach, A. T. N’Diaye, B. J. Kirby, E. Arenholz, and T. Tybell, Phys. Rev. B 94 (20), 201115 (2016).
11:15 AM - EM02.07.09
Elastomagnetoresistance of La0.7Sr0.3MnO3/Muscovite Heteroepitaxy
Min Yen 1 , Ying-Hao Chu 1
1 , National Chiao Tung University, Hsinchu City Taiwan
Show AbstractFlexible function attracts much attention on each research field in the last decade. Based on flexibility, we can directly apply elastic strain on the system and study the interaction which is induced by strain, unlike the way that we only can exert strain by the mismatch between film and hard substrate in the past. At the same time, La0.7Sr0.3MnO3(LSMO) which is a material with colossal magnetoresistance(CMR) property in perovskite structure, is believed that CMR performance is tunable by strain. However, there was a limitation that we can not apply strain arbitrarily. In this study, we choose muscovite as a flexible substrate to deposit LSMO thin film and utilize the advantage of flexibility that we can easily observe the coupling between elastic strain and magnetoresistance. To achieve high quality LSMO thin film on flexible muscovite, we deposit by pulsed laser deposition process and then Xray diffraction as well as the transmission electron microscopy will use to characterize the structures. Bending test is performed to demonstrate the tunability of functionalities by strain through bending. Magnetic and electrical measurements are performed using Superconducting Quantum Interference Device (SQUID) and Physical Properties Measurement System (PPMS) respectively. This system truly exhibits excellent magnetic and electrical properties with flexible characteristics and offers a pathway to fabricate flexible functional devices.
11:30 AM - *EM02.07.10
Ionic Liquid Gating of Fe3O4 with Giant Magnetoelectric Effect
Le Zhang 1 , Ziyao Zhou 1 , Weixiao Hou 1 , Guohua Dong 1 , Shishun Zhao 1 , Xu Xue 1 , Yijun Zhang 1 , Bin Peng 1 , Zhongqiang Hu 1 , Wei Ren 1 , Zuo-Guang Ye 1 2 , Ming Liu 1
1 , Xi’an Jiaotong University, Xi'an, Shaanxi, China, 2 , Simon Fraser University, Burnaby, British Columbia, Canada
Show AbstractVoltage controlling of magnetism via ionic liquid (IL) gating is of great importance in spintronics with both scientific interest and practical application potential due to the intriguing chemical, electronic and magnetic phenomenon at the interface[1, 2]. Numerous researches of IL gating on magnetism, particularly transportation properties, are reviewed, yet direct evidence and precise determination of magnetic anisotropy switching via voltages are crucial. Here we demonstrate a giant, reversible 922 Oe ferromagnetic resonance (FMR) field shift of Fe3O4 thin film induced by small gating voltage (Vg, +1.5 V, within the chemical window of IL) through IL gating structure Au/[DEME]+[TFSI]−/Fe3O4, referring to a record high magnetoelectric (ME) coefficient of 615 Oe/V. Under a larger Vg of 3 V (out the chemical window of IL), a much greater out-of-plane FMR field shift of 1572 Oe has been achieved with an enormous ME coefficient up to 524 Oe/V. These tremendous reversible and irreversible ME coupling tunabilities under Vg within or without chemical window were attributed to the decrease of Fe2+ and the increase of Fe3+ at the interface induced by electrostatic doping and electrochemical reaction correspondingly, as confirmed by EELS and XPS analysis. Moreover, the capacitance of the IL with the same DC bias as the Vg during the gating process gave directly proof of the relationship between charge density at the interface and the tunability. Interestingly, the Verwey transition temperature shows a strong dependence of Vg bias, revealing the potential of IL gating for controlling the intrinsic spin ordering of magnetic thin films. These findings prove that the IL gating structure is a very powerful tool in tuning magnetism of spinel ferrite thin film and its related applications.
Reference:
1. Zhao, S. S. et al., Quantitative Determination on Ionic-Liquid-Gating Control of Interfacial Magnetism, Adv.Mater. 2017 29 1606478.
2. Lu, N, P. et al., Electric-field control of tri-state phase transformation with a selective dual-ion switch, Nature 2017 doi:10.1038/nature22389.
3. Jeong, J. et al., Suppression of metal-insulator transition in VO2 by electric field-induced oxygen vacancy formation. Science 2013 339 1402–1405.
4. Li, H. P. et al., Polyfluorinated Electrolyte for Fully Printed Carbon Nanotube Electronics, Adv. Func. Mater. 2016 26 6914-6920.
EM02.08: Multiferroics III
Session Chairs
Wednesday PM, November 29, 2017
Hynes, Level 1, Room 107
1:30 PM - *EM02.08.01
Domain Dynamics in Multiferroics
Manfred Fiebig 1
1 Materials Department, ETH Zurich, Zurich Switzerland
Show AbstractThe functionality of any ferroic material depends on its domains. Consequently, their shape and manipulation are of major interest. In compounds uniting magnetic and electric order in the same phase, the magnetoelectric coupling on the level of the domains is, however, largely unexplored. For such so-called multiferroics it is therefore not known how exactly electric or magnetic fields or other external perturbations affect the multiferroic domains. Moreover, the coexistence of several multidimensional order parameters in multiferroics opens up unprecedented routes towards domain control that have not been discussed (or even realized) at all. In my talk, I will present examples for such domain dynamics in multiferroics and discuss their technological value. My examples will include: (1) Inversion of a ferromagnetic or ferroelectric domain pattern. Locally, the magnetization or polarization is reversed while leaving the domain pattern as such untouched. This can be regarded as ferroic NOT operation, or a ferroic analogue to "anti-noise". (2) Dynamics in the formation of improper ferroelectric domains in the hexagonal multiferroic manganites. Dynamic contributions I will identify are their topological nature, the cooling speed through the ordering temperature, and fundamental differences between bulk crystals and epitaxial thin films. Additional technological value arises from the coupling of the ferroelectric to the magnetic domain walls in the hexagonal manganites.
2:00 PM - EM02.08.02
Strain and Size Induced Effects in Thin Nickelate Films by Raman Spectroscopy
Alexander Schober 1 2 , Sara Catalano 3 , Mael Guennou 1 , Jean-Marc Triscone 3 , Hongjian Zhao 1 , Jorge Iniguez 1 , Jens Kreisel 1
1 Materials Research and Technology, Luxembourg Institute of Science and Technology, Esch-sur-Alzette Luxembourg, 2 , University of Luxembourg, Luxembourg Luxembourg, 3 Department of Quantum Matter Physics, University of Geneva, Geneva Switzerland
Show AbstractThe metal-to-insulator transition (MIT) of RNiO3 rare-earth nickelates has attracted the attention of various scientific communities in the past decades. It is closely controlled by the angles formed by the octahedra network in the perovskite structure, which makes it sensitive to the size of the rare-earth cation, but also to epitaxial strain, to size effects, or substrate orientation. Vibrational analysis through Raman spectroscopy is a classical and well adapted tool to track tilt angles and crystal structure in general, although signals can be weak for ultrathin films with very small scattering volume. In this work we show how Raman spectroscopy can be used to reveal changes in structure even for ultrathin films on two systems with different behaviours: Neodymium nickel oxide (NdNiO3) deposited on Neodymium gallium oxide (NdGaO3) and LaNiO3 deposited on Lanthanum aluminium oxide (LaAlO3).
We first analyze the phase transitions in a NdNiO3 thin film deposited epitaxially onto [111]pc pseudo-cubic oriented NdGaO3. The aim is to investigate the reported upward shift of the MIT temperature from 200K to 335K[1], and the dissociation of the MIT from the magnetic transition. We analyse the Raman signatures of both transitions and discuss them in relation with the phase diagram. This reported transition temperature would yield an O-Ni-O bonding angle equal to 158.8° according to the Nickelates phase diagram [2]. This is remarkably close to the tilts characterizing SmNiO3 [1] and therefore allows us to discuss on how strongly the structural transition governs MIT transition.
We also show evidence for size effects from the Raman spectra of LaNiO3 films ranging from 16 to 3 pseudo-cubic unit cells (~1.2 nm), obtained by an original procedure combining depth profile measurements with Principle component analysis. Bulk LaNiO3 is metallic at all temperatures, but when deposited on LaAlO3, it enters a resistive regime in the limit of ultrathin films, below 7 unit cells [3]. We extract the Raman signature of this ultrathin regime, and analyze it in combination it with first-principle calculations of the structural and vibrational properties of the films.
[1] S. Catalano, APL Materials, 3, 062506 (2015).
[2] G. Catalan, Phase Transitions, 81 (7-8), 729 (2008).
[3] J. Fowlie, Adv. Mat., 29(18), 1605197–5 ,(2017).
2:15 PM - EM02.08.03
Single Ferroelectric Transition of Weak First-Order in Multiferroic Hexagonal Manganite RMnO3
Hasung Sim 1 , Jaehong Jeong 1 , Sang Wook Cheong 2 , Je-Geun Park 1
1 Physics and Astronomy, Seoul National University, Seoul Korea (the Republic of), 2 , Rutgers, The State University of New Jersey, New Brunswick, New Jersey, United States
Show AbstractHexagonal manganite materials are multiferroic materials with two highly-dissimilar phase transitions: a ferroelectric transition (from P63/mmc to P63cm) at a temperature as high as 1450 °C and an antiferromagnetic transition at TN~75 K. Despite its critical relevance to the intriguing ferroelectric domain physics, the details of the ferroelectric transition are yet not well known to date primarily because of the ultra-high transition temperature. Here using high-resolution & high-temperature X-ray diffraction experiments we show that the ferroelectric transition is a single transition of weak first order and R-Op displacement is the primary order parameter. This structural transition is then simultaneously accompanied by MnO5 tilting and the subsequent development of polarization. Our work clarifies the question about the nature of the ferroelectric transition of hexagonal manganites, and shed light on the intriguing mechanism behind the domain physics of this material.
3:30 PM - *EM02.08.04
Coupled Multiple Order Parameters and Their Domain Switching in Magnetoelectrics
Tsuyoshi Kimura 1
1 , University of Tokyo, Chiba Japan
Show AbstractOne of the most important concepts in condensed matter physics is the spontaneous breakdown of symmetry in a solid, which bears the ordered phase and domains in its consequence. In magnetoelectric multiferroics, multiple order parameters coexist in a system, sometimes couple with each other, and exhibit nontrivial crossed phenomena. In this presentation, we deal with magnetoelectric multiferroics in which a symmetry breaking due to the orderings of various order parameters such as electric dipole, magnetic dipole, and magnetic quadrupole moments as well as chirality originating from these multipole moments. We show our recent research activity on exploration for new magnetoelectrics and manipulations of their multiple order parameters as well as domains. This work has been done in collaboration with T. Honda, J. S. White, M. Kenzelmann, A. B. Harris, K. Kimura, K. Yamauchi, M. Toyoda, P. Babkevich, H. M. Rønnow.
4:00 PM - *EM02.08.05
Ferroelectric Control of Ferrimagnetism Mediated by Charge Ordering
Shuai Dong 1
1 , Southeast University, Nanjing China
Show AbstractDespite various types of magnetoelectric coupling revealed in the past decade, a practical route to obtain electric-control-magnetism seems to be the carrier driven one, which occurs at the ferroelectric-magnet interfaces or multiferroic domain walls. In ferroelectric-manganite heterostructures, the magnetization of magnanite can be tuned by flipping the ferroelectric polarization. In this talk, I will introduce our theoretical designs to enhance this magnetoelectric effect, namely to control magnetization using electric field more efficiently. First, the magnitude of magnetization can be fully switched on/off in the manganite bilayer. Second, the inversion of magnetization can also been obtained in the [111]-oriented BiFeO3 few layers. Third, the inversion of magnetization can also been obtained in strained fluoride film.
4:30 PM - EM02.08.06
Multiferroic Oxide Nanocomposites with Rhombohedral and Tetragonal Bismuth Ferrite
Shuchi Ojha 1 , Shuai Ning 1 , C. A. Ross 1
1 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractVertically aligned two phase multiferroic nanocomposites have been widely studied for their potential application in future memory and logic devices since they enable control of both electric and magnetic order parameters. These nanocomposites exhibit strong room temperature magnetoelectric (ME) coupling mediated through strain at the interface between the ferri/ferromagnetic pillar phase (e.g. CoFe2O4 (CFO)) and the ferroelectric matrix phase (e.g. BiFeO3 (BFO) or BaTiO3). Several studies report magneto-electric coupling coefficients from the change in magnetic properties (coercivity or remanence) vs. electric field or the change in ferroelectric properties vs. magnetic field.
Here we show the growth of nanocomposites with a graded change in magnetic anisotropy, a key contributor to the magnetoelectric effect. The nanocomposites consist of BFO with pillars of (CoxNi1-x)Fe2O4, where x ranges from 0 to 1, grown by combinatorial pulsed laser deposition from three targets. The structure of the nanocomposites was similar but the anisotropy field varied from 8.6 kOe at x=1 to 3.5 kOe at x=0 due mainly to the high magnetostriction in CFO. Further, by modulating the epitaxial strain on BFO by utilizing different crystalline substrates LaAlO3, LSAT and SrTiO3, and underlayers LSMO and SrRuO3, we obtained different structures of BFO, rhombohedral (BFO-R) with c/a = 1 and tetragonal (BFO-T) with c/a = 1.2 and higher polarization. The changing structure of BFO affects not only the ferroelectric response of the material, but due to the large difference in c/a ratio, results in different interface strains and hence magnetoelastic anisotropy in the CFO.
We quantify the ME coupling coefficient to correlate it to specific changes in materials properties such as magnetic anisotropy, ferroelectric response and interface strain. The coupling is quantified at the local scale by measuring the ferroelectric response of the films while applying in-situ magnetic fields ranging from 0 to 2000 Oe, by using a variable field module attachment for piezoresponse microscopy (PFM). The measurements are done in dual AC resonance tracking mode, to enhance the sensitivity of the measurements by tracking the resonance frequency of the cantilever. The coupling coefficient can be quantified by extracting the d33 coefficient of the films from the amplitude curves obtained from switching spectroscopy PFM measurements. The ME coupling coefficient can then be calculated as a change in the d33 coefficient divided by change in magnetic field. Qualitative changes in ferroelectric domain structure can be observed by looking at PFM scans before and after the application of magnetic fields.
EM02.09: Poster Session III: Multiferroics
Session Chairs
Tommaso Costanzo
Alexander Schober
Thursday AM, November 30, 2017
Hynes, Level 1, Hall B
8:00 PM - EM02.09.01
Unconventional Charge Ordering in 3D Metallic Single Crystal of Na2.7Ru4O9
Arvind Yogi 1 2 , C. I. Sathish 1 2 , Hasung Sim 1 2 , Yukio Noda 3 , Je-Geun Park 1 2
1 , Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul Korea (the Republic of), 2 , Department of Physics and Astronomy, Seoul National University, Seoul Korea (the Republic of), 3 , Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai Japan
Show AbstractWe report a comprehensive investigation of the structural, electric transport, magnetic, and thermodynamic properties of Na2.7Ru4O9 single crystals. Na2.7Ru4O9 crystalize in monoclinic structure with P 21/m space group. We observed a first-order phase transition in the electrical resistivity with two consecutive transitions at Tc (1) = 365 K and Tc (2) = 345 K for Na2.7Ru4O9, which is supported by magnetization and heat-capacity results. The electron–phonon mediated scattering mechanism is involved in the resistivity of Ru-based metallic system. The evidence of metal-like electronic contribution was also observed in the low-temperature heat capacity. The electronic contribution to the specific heat (γ) for Na2.7Ru4O9 was determined to be 26.91 mJ/mol K2. Magnetic susceptibility c(T) = M/H curve shows a broad hump near the first order phase transition for Na2.7Ru4O9, indicating the coexistence of short range correlations. The temperature-dependent SC-XRD results shows superlattice-peaks q1(0, 1/2, 0) and q2(1/3, 1/3, 0), which get substantially suppressed at higher temperatures. The suppression of the superlattice peaks is viewed as a Na+ ion motion in the Na2.7Ru4O9 lattice, which is responsible for increased localization of 4d Ru4+ (S = 0) low spin state t2g (2) ↑ t2g (2) ↓ without the loss of metallicity.
8:00 PM - EM02.09.02
The Effect of Oxygenation on the Ferroelectric Performances of Bismuth Ferrite Thin Films
Bahadir Can Kocaoglu 1 , Ahmet Macit Ozenbas 1
1 , Orta Dogu Teknik University, Ankara Turkey
Show AbstractA novel precursor solution enabling excellent coating thickness, stoichiometry and oxygenation control on bismuth ferrite (BFO) coatings on fluorine doped tin oxide (FTO)/glass and Pt/Ti/SiO2/Si using chemical solution deposition method was optimized. The oxygen vacancy concentration and/or exact stoichiometry of BFO coatings were adjusted precisely using secondary heat treatment at 600 oC for a few minutes to 4 hours and UV-Ozone treatment. XPS analysis exhibited the change in the oxygen content depending on the heat treatment and/or UV-Ozone treatment duration, while XRD analysis confirmed the absence of secondary or formerly precipitated phases, indicating almost total purity. The coating thickness, morphology and homogeneity of the coatings were analyzed via SEM analysis such that the coating thickness and homogeneity of the coatings were confirmed to exhibit extreme precision on the order of a few nm to 500 nm. Depending on the oxygen content and the substrate-coating interaction nature, the ferroelectric performances were investigated. The change in the polarization and remnant polarization values were measured for the coatings heat treated at distinct durations and enhancements on maximum polarization values and hysteresis curves were observed while decrease in the leakage was denoted as well. The maximum polarization values were enhanced from 0.03 and 0.05 µC/cm2 to 0.1 and 0.13 µC/cm2 at around 40 kV/cm2 for the coatings on FTO/Glass and Pt/Ti/SiO2/Si substrates, respectively.
8:00 PM - EM02.09.03
Multifunctional Properties of Epitaxial LaNiO3/LaCoO3 Thin Films Fabricated by Pulsed Laser Deposition
Rambabu Angalakurthi 1 , Krupanidhi S. B 1 , Sundaresan Athinarayanan 2
1 , Indian Institute of Science, Bangalore, KA, India, 2 , Jawaharlal Nehru centre for Advanced Scientific Research, Bangalore, Karnataka, India
Show AbstractThin films, multilayers and the phenomena associated to their interfaces have attracted the interest of scientific community due to the possibility of tunning their magnetic/electronic properties by epitaxial strain or by the electronic reconstruction induced at the contact between two different materials. Nowadays, the electronic reconstruction at oxides interface is a topic of intense investigation, due to the appearance of unexpected properties in layered structures. R. Pentcheva et.al.[1] showed that besides extrinsic factors as oxygen vacancies and strains, the effect of charge re-accommodation in the atomic layers close to interfaces needs to be taken into account to understand some of the properties of oxide based heterostructures. The observation of exchange bias effect at the ferromagnetic/antiferromagnetic oxide-based super lattices was first reported a few years ago. However, there are still many open questions to solve in this matter. The interest in this effect and the exploration of the leading mechanism has been renewed in the last decades. The possibility of building artificial structure with controlled interfaces has allowed researchers to get a deeper insight in the characteristics and origin of the phenomena [2-3].
We report the synthesis of individual and multilayer of epitaxial LaNiO3/LaCoO3 (LNO/LCO) on (100) LaAlO3 by pulsed laser deposition. Their structural and morphological studies were examined by XRD and FESEM respectively. It was observed that bilayer/multilayer of LNO/LCO showed increase in magnetic properties compared to individual LCO or LNO films. The magnetoresistance was varying from negative to positive as the temperature varies from 20-300K. Interestingly, bilayer/multilayer films exhibited the improved magnetic and transport properties. We suggest that the origin of this effect is a strong Ni3+-O-Co3+ exchange interaction at the interface. Our result demonstrates that bilayer/multilayer of LNO/LCO is able to produce multifunctional properties which can be useful in spintronic applications.
Reference:
R. Pentcheva, W. E. Pickett, Phys. Rev. 78, 205106, (2008).
J. Nogues, I. K. Schuller, J. Magn. Magn. Mater. 192, 203 (1999).
M. Kiwi, J. Magn. Magn. Mater. 234, 584, (2001).
8:00 PM - EM02.09.04
Novel Engineered Ferroelectric Thin Films for Energy Storage Applications
Sita Dugu 1 , Alvaro Instan Ballesteros 1 , Dhiren Pradhan 2 , Mohan Bhattarai 1 , Ram Katiyar 1
1 , University of Puerto Rico, San Juan, Puerto Rico, United States, 2 , Geophysical Laboratory, Washington, District of Columbia, United States
Show AbstractRecently ferroelectric nanostructures have attracted attention to the scientific community owing to both fundamental scientific interest as well as the possibility of well regulated energy and information storage. The slim hysteresis of relaxor ferroelectrics provides high electric displacement or charge density, a large area to store the energy and fast discharge capacity. Zn doped BTO thin films were grown on commercially available platinized silicon substrates utilizing optimized pulsed laser deposition (PLD) with an excimer laser (KrF, 248 nm). Zn doped BTO thin films were deposited at an optimized temperature of 700°C under an oxygen pressure of 100 mTorr, having a laser energy density ~ 1.5 J/cm2 with a frequency of 5 Hz. Then the thin films were annealed at same growth temperature in an oxygen atmosphere of 300 Torr for 30 minutes and later cooled down to room temperature slowly. The θ-2θ large angle x-ray scans (20° to 80°) showed only diffraction peaks from the substrate and pseudocubic reflections from the material confirms that these films are polycrystalline in nature. The AFM studies revealed that the surfaces of all the thin films are observed to be smooth and very homogeneous, free of microcracks, pores or holes with average surface roughness around 2-3 nm. The existence of ferroelectricity at the nanoscale has been confirmed by PFM measurement. This thin film exhibits saturation polarization of 43µC/cm2, remanent of 7 µC/cm2 and 0.06MV/cm coercive field. Temperature dependence of ferrolectric hysteretic behavior has also been studied. The nanostructures show well saturated large polarization, low loss tangent, good recoverable energy storage densities and energy storage efficiencies well above the room temperature which may be useful for nanoscale multifunctional device applications.
8:00 PM - EM02.09.05
Mechine Learning of Polar Vortices in Ferroelectric Superlattices
Qian Li 1 , Christopher Nelson 2 , Lane Martin 2 , Ramamoorthy Ramesh 2 , Sergei Kalinin 1
1 Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, California, United States
Show AbstractFlexoelectricity refers to electric polarization generated by heterogeneous mechanical strains (namely, strain gradient) in a material of arbitrary crystal structure symmetries. Despite over 50 years’ recognition of this effect, an accurate identification of its coupling strength remains a challenge. Here, we use machine vision approaches applied to the atomically resolved scanning transmission electron microscopy (STEM) data set of PbTiO3/SrTiO3 polar vortex superlattices, a recently discover system showing exotic polarization topology and mesoscopic ordering [Nature 530, 198 (2016)]. From this analysis, we extract the maximum global characteristics of the vortex structure which hints at flexoelectricity. Phenomenological phase-field modeling has then been performed to systematically survey the influence of flexocoupling on the vortex structure. Furthermore, we match the modeling and experiment results via direct correlative analysis, thus making a clear-cut determination of the flexoelectric coefficients for PbTiO3 and SrTiO3. Our findings highlight the inherent, nontrivial role of flexoelectricity in the generation of emergent complex polarization topologies of condensed matters. The approach we have developed here also illustrates how high-veracity atomically-resolved images of materials can be harnessed for elucidating physical parameters at a continuum theory level via computer vision methodologies, and potentially can be applied to other mesoscopically ordered systems including vacancy dynamics, chemical reactions, etc.
Ref. Qian Li et al, submitted (2017)
8:00 PM - EM02.09.06
Determining Phase Transitions in Ferroic Materials via Machine Learning of Dynamic Responses
Linglong Li 1 2 , Zuo-Guang Ye 3 , Stephen Jesse 1 , Sergei Kalinin 1 , Rama Vasudevan 1
1 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi'an, Shaanxi, China, 3 Department of Chemistry and 4D LABS, Simon Fraser University, Burnaby, British Columbia, Canada
Show AbstractThe detection of phase transitions and mapping phase diagrams of structural, electronic, topological and other phases constitutes a major portion of modern condensed matter physics. For multiferroic materials where the order parameters are known, these provide a method to determine the onset and boundaries of the phase diagram; however in many situations the order parameters are difficult to measure, unknown, or non-local, complicating the situation. Moreover, in local measurements most of the degrees of freedom are hidden, underlying mechanisms are unknown, and thus determining phase transitions is more troublesome. Here, we present a method to determine phase transitions and map phase diagrams via exploring the collective dynamics of the system using piezoresponse force microscopy. We apply the technique experimentally to a relaxor ferroelectric system 0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 under electrical and thermal stresses. Subsequently, basic machine learning analysis of the relaxation dynamics, including principal component analysis and k-means clustering, allows us to recreate the temperature-bias structural phase diagram. Thus, the use of machine learning allows us to construct the phase diagram without the need for physics-based labeling or knowledge of the Hamiltonian, using only local measurements which serve as proxies to dynamics of the hidden structural phases through which the system transitions. This research was sponsored by the Division of Materials Sciences and Engineering, BES, DOE (RKV, SVK). This research was conducted at and partially supported (SJ) the Center for Nanophase Materials Sciences, which is a US DOE Office of Science User Facility. L. L. acknowledges financial support from Chinese Scholarship Council. Z.-G.Y. acknowledges the support from the U.S. Office of Naval Research (ONR Grants No. N00014-12-1-1045 and N00014-16-1-6301) and the Natural Sciences and Engineering Research Council of Canada (NSERC, Grant No. 203773).
8:00 PM - EM02.09.07
Ultrafast Dynamics of Photoexcited Quasiparticles in Correlated Polar Metal Ca3Ru2O7
Yakun Yuan 1 , Peter Kissin 2 , Shiming Lei 1 , Richard Averitt 2 , Venkatraman Gopalan 1
1 , The Pennsylvania State University, University Park, Pennsylvania, United States, 2 Physics, University of California, San Diego, La Jolla, California, United States
Show AbstractPolar metals [1] are exotic materials where two contradictory properties, metallicity and ferroelectric-like distortions, coexists inside one material, providing a unique platform for exploring quasiparticles dynamics within an intrinsic polar lattice. As a member of the rare polar metal family, Ca3Ru2O7 also exhibits a rich range of phenomena, such as two metal insulator transitions, two magnetic transitions and ferroelectric-like lattice distortion. In this work, we focused on understanding the electronic structures near fermi level, as well as the dynamics of quasiparticles in correlated Ca3Ru2O7.
By optically exciting a non-thermal electron distribution using a femtosecond laser pulse and probing optical reflectivity, one can learn the electronic structure and the coupling between electrons, phonons and magnons in a material. [2] We performed systematic temperature dependent time-resolved photo-induced reflectivity from 300K down to 10K. An intriguing slow rise dynamics starting from 70K indicates the emerging of pseudogap at this temperature, which is higher than previous reported ~48K measured by IR reflectivity [3]. This suggests the antiferromagnetic and structural transitions at 48K is possibly driven by this electronic transition. We also observed a three-stage relaxation process with decay time constants of 0.1-10ps, ~50ps and >500ps, which respectively correspond to electron-phonon scattering, electron-magnon scattering and phonon dissipation. A number of physical quantities, such as the size of the pseudogap, heat capacity and thermal conductivity, are extracted from modeling the dynamic behavior of Ca3Ru2O7.
This work is supported by DOE DE-SC 00012375 and DMR 1420620.
1. Nature 533, 68-72 (2016)
2. J. Phys.: Condens. Matter 18 (2006) R281–R314
3. PRL 98, 097403 (2007)
8:00 PM - EM02.09.08
Annealing of YIG/Pt Heterostructures—Structural Changes Induced by Post Deposition Processing
Kevin Geishendorf 1 , Andy Thomas 1 , Stephan Geprägs 2 , Sebastian Goennenwein 2 3 , Kornelius Nielsch 1 3
1 , Leibniz Institute for Solid State and Materials Research, Dresden Germany, 2 , Walther-Meißner-Institute, Garching Germany, 3 , Technische Universität Dresden, Dresden Germany
Show AbstractYttrium-Iron-Garnet (YIG) based heterostructures provide a model system of ferromagnetic/non- magnetic bilayers, widely used to study spin injection processes, influencing the magnetodynamics of a ferromagnetic layer. Measurements of the spin Hall magnetoresistance or magnon mediated magnetoresistance are powerful tools to study the correlation between magnetodynamics and the voltage applied to the nonmagnetic layer. Superlattice structures consisting of several repeating YIG/Pt bilayers could reveal fascinating phenomena deriving from interference effects. The growth of such multilayered systems indispensably requires annealing of YIG in contact with Pt. In this work YIG/Pt heterostructure were deposited and subsequently annealed to investigate the influence of annealing on the bilayers. Different X-ray techniques, atomic force microscopy and transport measurements were carried out to compare the as deposited with the annealed state. With increasing temperatures structural changes of the platinum layer occur. Recrystallization, island formation and most important the formation of an intermetallic Fe-Pt phase at the interface were observed. The spin injection properties of the heterostructures were qualitatively determined with measurements of the spin Hall magnetoresistance. The effect decreased almost one order of magnitude after the annealing process, pointing out the sensitivity of spin injection properties against structural changes. Overall, this work supplied valuable insights on the optimization of multilayered ferromagnet/non-magnetic structures with respect to the interfacial and thin film quality.
Symposium Organizers
Nian Sun, Northeastern University
Franz Faupel, Kiel University
Cewen Nan, Tsinghua University
Ramamoorthy Ramesh, University of California, Berkeley
EM02.10: Magnetoelectrics IV
Session Chairs
Thursday AM, November 30, 2017
Hynes, Level 1, Room 107
8:00 AM - *EM02.10.01
Atomic Engineering of Ferroic Layers to Create a Room-Temperature Magnetoelectric Multiferroic
Julia Mundy 1 , Charles Brooks 2 , Megan Holtz 1 , Jarrett Moyer 3 , H. Das 1 , Alejandro Rebola 1 , Elizabeth Nowadnick 1 , R. Steinhardt 2 , John Heron 2 , James Clarkson 4 , Steve Disseler 5 , Z. Liu 6 , Alan Farhan 7 , R. Held 2 , Robert Hovden 1 , Elliot Padgett 1 , Q. Mao 1 , Hanjong Paik 2 , R. Misra 8 , Lena F Kourkoutis 1 9 , Elke Arenholz 7 , Andreas Scholl 7 , Julie Borchers 5 , William Ratcliff 5 , Ramamoorthy Ramesh 4 , Craig Fennie 1 , Peter Schiffer 3 , David Muller 1 9 , Darrell Schlom 2 9
1 School of Applied and Engineering Physics, Cornell University, Ithaca, New York, United States, 2 Department of Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 3 Department of Physics and Frederick Seitz Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 4 Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, California, United States, 5 Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland, United States, 6 Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania, United States, 7 Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 8 Department of Physics, Pennsylvania State University, University Park, Pennsylvania, United States, 9 , Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York, United States
Show AbstractMaterials that exhibit simultaneous order in their electric and magnetic ground states hold tremendous promise for use in next-generation memory devices in which electric fields control magnetism. Such materials are exceedingly rare, however, due to competing requirements for displacive ferroelectricity and magnetism. Despite the identification of a number of novel multiferroic materials and magnetoelectric mechanisms recently, known single-phase multiferroics remain limited by antiferromagnetic or weak ferromagnetic alignments, lack of coupling between the order parameters, or have properties that only emerge well below room-temperature, stymieing device applications. We present a new methodology for the construction of single-phase multiferroic materials where ferroelectricity and strong magnetic ordering are coupled near room-temperature [1]. Starting with hexagonal LuFeO3, a geometric ferroelectric with the greatest known planar rumpling, we introduce individual extra monolayers of FeO during growth to construct formula-unit-thick syntactic layers of ferrimagnetic LuFe2O4 within the LuFeO3 matrix, i.e., (LuFeO3)m/(LuFe2O4)1 superlattices [1]. The severe rumpling imposed by the neighbouring LuFeO3 drives the ferrimagnetic LuFe2O4 into a simultaneously ferroelectric state, while also reducing the LuFe2O4 spin frustration. This increases the magnetic transition temperature significantly—from 240 K for LuFe2O4 to 281 K for (LuFeO3)9/(LuFe2O4)1. Moreover, the ferroelectric order couples to the ferrimagnetism, enabling direct electric field control of magnetism at 200 K. Our results demonstrate a design methodology for creating higher-temperature magnetoelectric multiferroics by exploiting a combination of geometric frustration, lattice distortions, and epitaxial engineering [1].
[1] J.A. Mundy, C.M. Brooks, M.E. Holtz, J.A. Moyer, H. Das, A.F. Rébola, J.T. Heron, J.D. Clarkson, S.M. Disseler, Z. Liu, A. Farhan, R. Held, R. Hovden, E. Padgett, Q. Mao, H. Paik, R. Misra, L.F. Kourkoutis, E. Arenholz, A. Scholl, J.A. Borchers, W.D. Ratcliff, R. Ramesh, C.J. Fennie, P. Schiffer, D.A. Muller, and D.G. Schlom, “Atomically Engineered Ferroic Layers Yield a Room-Temperature Magnetoelectric Multiferroic,” Nature 537 (2016) 523–527.
8:30 AM - *EM02.10.02
Magneto-Electric Interactions in Ferrite-Ferroelectric Coaxial Nanofibers and Superstructures Assembled in Magnetic Fields
Gollapudi Sreenivasulu 1 , Ru Zhang 1 , Maksym Popov 1 , Jitao Zhang 1 , Gopalan Srinivasan 1
1 , Oakland University, Rochester, Michigan, United States
Show AbstractThis report is on the synthesis of nickel ferrite (NFO) -barium titanate (BTO) and NFO-lead zirconate titanate (PZT) core-shell nano-fibers, assembly into films in a magnetic field, and studies on magneto-electric interactions (ME) interactions. Electrospinning techniques were used to prepare coaxial fibers of 0.5-2 micron in diameter. The core-shell structure of annealed fibers was confirmed by scanning electron microscopy and scanning probe microscopy. The fibers were assembled into discs and films in a uniform magnetic field or a field gradient.1,2 Studies on ME coupling in the assembled films and discs were done by magnetic field H induced polarization, magneto-dielectric effects at low frequencies and at 16-24 GHz, and low frequency ME voltage coefficients (MEVC). We measured 7-33 % change in remnant polarization for H = 7 kOe, 2- 7 % change in magnetic field induced change in the permittivity, and a low-frequency MEVC of 0.4 mV/cm Oe at 30 Hz. Models for the magneto-dielectric effect and low-frequency ME effects have been developed and estimates of strength of ME coupling are compared with the data. These results indicate strong ME coupling in the magnetic field assembled superstructures of the core-shell fibers.
- Research supported by a grant from the NSF.
1. G. Sreenivasulu, Maksym Popov, Ru Zhang, K. Sharma, C. Janes, A. Mukundan, and G. Srinivasan, Appl. Phys. Lett. 104, 052910 (2014).
2. M. Lorenz, M. S. Ramachandra Rao, T Venkatesan, et. al., J. Phys.D: Appl. Phys. 49, 433001 (2016).
9:00 AM - EM02.10.03
Ferroelectric Phase Transition Induced a Large FMR Tuning in Self-Assembled BaTiO3:Y3Fe5O12 Multiferroic Composites
Guohua Dong 1 , Ziyao Zhou 1 , Xu Xue 1 , Yijun Zhang 1 , Bin Peng 1 , Mengmeng Guan 1 , Shishun Zhao 1 , Zhongqiang Hu 1 , Wei Ren 1 , Zuo-Guang Ye 2 , Ming Liu 1
1 , Xi'an Jiaotong University, Xi'an China, 2 , Simon Fraser University, Burnaby, British Columbia, Canada
Show AbstractFor decades, although a great deal of research has been done in spinel ferrite based multiferroic [1, 2], the high loss and energy consuming lead to limiting their application in GHz frequency devices. Therefore, tuning of Y3Fe5O12 (YIG) based multiferroics is of great importance for its low loss, low linewidth and large band gap[3], yet, it is very challenge due to its near zero magnetostriction and the difficulty of building epitaxial interface between ferromagnetic garnet and ferroelectric phases. Therefore, few works have been done due to this fundamental challenge.
In this work, we initialed to construct a self-assembled YIG garnet and BaTiO3 (BTO) perovskite vertically aligned composite structure by PLD. The single crystal, cubic shape of BTO nano-pillars are embedded into YIG matrix, confirming by scanning transmission electron microscopy and energy dispersive spectrometer, which behaves differently from the majority of spinel and perovskite composite films. These 1-3 type composites - vertical aligned nanocomposite multiferroic thin films exhibit a much greater magnetoelectric (ME) coupling coefficient for its negligible clamping constraints from the substrate and the larger interfacial area between the two phases. [4] Most interestingly, local epitaxial interfaces between ferromagnetic garnet and ferroelectric perovskite phases were discovered and studied by atomic-scale STEM. Large ME coupling that drives FMR shift up to 512 Oe and 333 Oe are obtained through BTO phase transition at 295K and 193 K, respectively, breaking the state of the art YIG tunability [5] with 1-2 order magnification. Giant ME coupling coefficients during transition are calculated as 256 Oe/K and 166 Oe/K, correspondingly. This novel YIG:BTO vertical local epitaxial growth multiferroic heterostructure enables the tunable YIG based microwave devices, where the FMR can be modulated by small thermal variation near the room temperature.
Reference
1. Lu, S. Z., et al., Epitaxial growth of Ni0.5Zn0.5Fe2O4+BiFeO3 composite films on SrTiO3 substrates. J. Alloys Compd. 2017, 708, 194-201.
2. Amrillah, T., et al., Tuning the magnetic properties of self-assembled BiFeO3-CoFe2O4 heteroepitaxy by magneto-structural coupling. Nanoscale 2016, 8, 8847-8854.
3. Yang, X., et al., Recent advances in multiferroic oxide heterostructures and devices. J. Mater. Chem. C 2016, 4, 234-243.
4. Zhang, W., et al., Interfacial coupling in heteroepitaxial vertically aligned nanocomposite thin films: From lateral to vertical control. Curr. Opin. Solid St. M. 2014, 18, 6-18.
5. Das, J., et al., Electric-Field-Tunable Low Loss Multiferroic Ferrimagnetic-Ferroelectric Heterostructures. Adv. Mater. 2009, 21, 2045-2049.
9:15 AM - *EM02.10.04
Integrated Magnetics and Multiferroics for Compact and Power Efficient Sensing, Power, RF, Microwave and mm-Wave Tunable Electronics
Hwaider Lin 1 , Nian Sun 1
1 , Northeastern University, Boston, Massachusetts, United States
Show AbstractThe coexistence of electric polarization and magnetization in multiferroic materials provides great opportunities for realizing magnetoelectric coupling, including electric field control of magnetism, or vice versa, through a strain mediated magnetoelectric coupling in layered magnetic/ferroelectric multiferroic heterostructures [1-9]. Strong magnetoelectric coupling has been the enabling factor for different multiferroic devices, which however has been elusive, particularly at RF/microwave frequencies. In this presentation, we will cover the most recent progress on new integrated multiferroic materials and devices for sensing, and from power to mm-wave electronics. Specifically, we will introduce magnetoelectric multiferroic materials, and their applications in different devices, including: (1) ultra-sensitive magnetometers based on RF NEMS magnetoelectric sensors with picoTesla sensitivity for DC and AC magnetic fields, which are the best room temperature nano-scale magnetometers; (2) novel ultra-compact multiferroic antennas immune from ground plane effect with Φ200µm × 1µm or λ/600 in size, -18dBi gain, self-biased operation and 1~2% voltage tunable operation frequency; and (3) novel GHz magnetic and multiferroic inductors with a wide operation frequency range of 0.3~3GHz, and a high quality factor of close to 20, and a voltage tunable inductance of 50%~150%. At the same time, I will also demonstrate other voltage tunable multiferroic devices, including tunable isolating bandpass filters, tunable bandstop filters, tunable phase shifters, etc. These novel integrated multiferroic devices show great promise for applications in compact, lightweight and power efficient sensing, power, RF, microwave and mm-wave integrated electronics.
Reference: 1. N.X. Sun and G. Srinivasan, SPIN, 02, 1240004 (2012); 2. J. Lou, et al., Advanced Materials, 21, 4711 (2009); 3. J. Lou, et al. Appl. Phys. Lett. 94, 112508 (2009); 4. M. Liu, et al. Advanced Functional Materials, 21, 2593 (2011); 5. T. Nan, et al. Scientific Reports, 3, 1985 (2013); 6. M. Liu, et al. Advanced Materials, 25, 1435 (2013); 7. M. Liu, et al. Advanced Functional Materials, 19, 1826 (2009); 8. Ziyao Zhou, et al. Nature Communications, 6, 6082 (2015). 9. T. Nan, et al. Nature Communications. in press.
9:45 AM - EM02.10.05
Room Temperature Spin-Orbit Torque Switching Induced by a Topological Insulator
Jiahao Han 1 , Anthony Richardella 2 , Saima Siddiqui 1 , Joseph Finley 1 , Nitin Samarth 2 , Luqiao Liu 1
1 Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 , The Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractRecent studies on the magneto-transport properties of topological insulators (TI) have attracted great attention due to the rich spin-orbit physics and promising applications in spintronic devices. Particularly, the strongly spin-moment coupled electronic states have been extensively pursued to realize efficient spin-orbit torque (SOT) switching. However, so far current-induced magnetic switching with TI has only been observed at cryogenic temperatures. Moreover, very controversial results of calibrating the figure of merit for charge-spin conversion, i.e., the effective spin Hall angle, have been reported using different methods. It remains unclear whether topologically protected electronic states in TI could be robust enough to benefit spintronic applications at room temperature.
Here we report full SOT switching in a TI/ferromagnet heterostructure with perpendicular magnetic anisotropy (PMA) at room temperature. The ferrimagnetic cobalt-terbium (CoTb) alloy with robust bulk PMA, which overcomes the difficulty of achieving perpendicular anisotropy with large interfacial lattice mismatch, is directly grown on the TI material Bi2Se3. The switching curve changes its polarity when the in-plane bias field is inversed, which is a typical characteristic of the SOT switching of PMA films. The low switching current density (~ 3 × 106 A/cm2) provides definitive proof of the high SOT efficiency from TI and suggests the topological spin-momentum locking even if it is neighbored by a strong ferromagnet. The SOT efficiency is measured by the current-induced shift of the Hall resistance-vs-magnetic field hysteresis loops with various in-plane bias fields. The SOT efficiency grows linearly in magnitude for small bias fields and reaches saturation at a critical value, which is consistent with the model of the current-induced Néel domain wall expansion. Accordingly, the effective spin Hall angle in our studied TI is determined to be 0.16, much higher than the values obtained from control samples of Ta and Pt using the same experimental techniques (0.16, 0.017, and – 0.031, respectively). And the opposite sign of the spin Hall angles of Bi2Se3 and Ta rules out the possibility that the spin-orbit coupling from the heavy element Tb plays the dominant role in the SOT switching Furthermore, we calculate the power consumption for switching a ferromagnetic layer with Bi2Se3, Pt, and Ta, and find that the magnetization switching with TI presents much higher energy efficiency than the heavy metals. We note that to minimize the electrical shunting effects of the ferromagnetic layer and fully exploit the efficiency of TI, magnetic semiconductors/insulators such as rare earth iron garnet or barium ferrite with PMA would be favorable. Our results demonstrate the robustness of TI as an SOT switching material and provide an avenue towards applicable TI-based spintronic devices.
10:30 AM - *EM02.10.06
Giant Anisotropic Nonlinear Optical Responses in 2D Multiferroic Materials
Hua Wang 1 , Xiaofeng Qian 1
1 , Texas A&M University, College Station, Texas, United States
Show AbstractOwing to the absence of spatial inversion and/or time-reversal symmetry, multiferroic materials naturally hold nonlinear optical responses that are of crucial importance for many technologically important applications such as lasers, frequency conversion, electro-optic modulators, and nonlinear optical sensing. The strength of their nonlinear response is essentially governed by intrinsic crystal symmetry, microscopic transition dipole moments, and local physical and chemical environment, while dimensionality reduction could dramatically impact all these factors. Here we present our first-principles theoretical discovery and microscopic understanding of giant ferroelectric-ferroelastic multiferroicity and extraordinary second harmonic generation (SHG) in two-dimensional monolayer group IV monochalcogenides whose 3D bulk is centrosymmetric with vanishing second order optical response. Remarkably, the strength of their SHG susceptibility is much higher than that in monolayer MoS2 and hexagonal BN, and the corresponding polarization anisotropy is intrinsically correlated with the strongly coupled ferroelastic and ferroelectric orders. More importantly, we will also present the microscopic mechanisms of the large multiferroicity and nonlinear responses at the first-principles theory level, which will be particularly vabluable for discovering and designing new ferroelectric-ferroelastic multiferroic materials with large nonlinear responses. Our present findings not only provide a fundamental understanding of the large nonlinear susceptibility in these 2D group IV monochalcogenides and the corresponding materials design rules, but also open up a variety of new avenues for ultrathin ferroelectrics, multiferroics, and optoelectronics with coupled nonlinear multiphysical responses. (References: 1. Two-dimensional multiferroics in monolayer group IV monochalcogenides. 2D Materials 4, 015042 (2017). 2. Hua Wang and Xiaofeng Qian. Giant Optical Second Harmonic Generation in 2D Multiferroics (2017, submitted).)
11:00 AM - EM02.10.07
Flexible Co-Based Heusler Alloy/Muscovite Heteroepitaxy
Yi-Cheng Chen 1 2 , Min Yen 1 , Anastasios Markou 2 , Benedikt Ernst 2 , Claudia Felser 2 , Ying-Hao Chu 1
1 Materials Science and Engineering, National Chiao Tung University, Hsinchu Taiwan, 2 , Max Planck Institute for Chemical Physics of Solids, Dresden Germany
Show AbstractCo-based ferromagnetic Heusler alloys show spin polarization up to 60% with a high Curie temperature of ~700K [1]. This feature provides the spin current which is usually applied to the ferromagnetic electrode in spintronic devices. In this study, we demonstrate the epitaxy of Co2MnGa Heusler alloy on flexible muscovite substrate, which paves a way toward flexible spintronic devices. The epitaxial Co2MnGa Heusler/muscovite heterostructure was prepared by magnetron sputtering. We applied three targets (Co, Mn, and MnGa) as the deposition sources to manipulate this composition-sensitive thin film. Muscovite is chosen as the flexible substrate for Heusler alloy since its high melting point meets growth condition for epitaxy. The epitaxy is characterized by X-ray diffraction with the epitaxial relationship of [110] Mica||[1-10]Co2MnGa. The lattice parameter of the film is 5.761A (Bulk: 5.770A) which shows nearly no strain exerted on the film. The composition was determined by Energy-dispersive X-ray spectroscopy (EDX). The in-plane magnetic hysteresis loops measured by SQUID show the saturated magnetization is ~755 emu/cc and coercivity field is ~102 Oe at room temperature. Compare to FePt (1140 emu/cc), the saturated magnetization is relatively low. This relatively small value causes lower energy consumption during the magnetization switch process. After characterizing the physical properties, we apply various bending test to investigate the performance of the film. The bending result shows the magnetization and transport properties of the thin film were modulated. The saturated magnetization is 7.6% higher under bending condition. The electrical resistance was measured on a custom bending stage which could vary the bending radius of the sample. The resistance is changed while the bending radius is decreasing, and it goes back to the original state after releasing the sample. The demonstration of Co2MnGa/muscovite heteropeitaxy provides a new perspective on developing the spintronic devices and a huge potential for application of next-generation spintronic devices.
[1] B.S.D.C.S. Varaprasad, A. Srinivasan, Y.K. Takahashi, M. Hayashi, A. Rajanikanth, K. Hono,
Acta Mater. 60, 6257 (2012)
11:15 AM - EM02.10.08
Stabilization of a Néel Skyrmion Lattice in Iridate-Manganite Heterostructures
John Nichols 1 , Satoshi Okamoto 1 , Thomas Farmer 1 , Ho Nyung Lee 1
1 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractRecent studies have revealed novel magnetic properties at 3d-5d oxide heterointerfaces between iridates and manganites. Examples of such states include charge transfer induced magnetism at both Ir and Mn sites that originates from the formation of molecular orbitals; the emergence of a magnetism driven anomalous Hall effect; and control of both the magnetic easy axis and relative orientation of the magnetization by engineering the sample geometry. To further advance the fundamental understanding of strongly spin-orbit entangled interfaces, we have investigated a series of (LaMnO3)m(SrIrO3)n superlattices grown on (001) SrTiO3 substrates by pulsed laser epitaxy. We have studied the structural, magnetic, and electronic properties of these superlattices utilizing numerous experimental and theoretical techniques and observed a variety of novel physical properties. From investigations of the physical properties through transport and Hall measurements, we discovered the anomalous Hall effect (AHE) in all samples below and near the Curie temperature (TC). However, for samples with intermediately thick sublayer thicknesses, we observed a large deviation from the standard AHE behavior at high magnetic fields. This strong deviation arises as a consequence of the topological Hall effect owing to the presence of a noncollinear spin texture. Through both model Hamiltonian calculations and simulations of the micro magnetic structure utilizing the object oriented micro magnetic framework, we conclude that the observation of the topological Hall effect originates from the formation of a lattice of Néel skyrmions. Thus, this unprecedented observation of a robust skyrmion lattice in an all oxide system demonstrates the great potential of SrIrO3 for the development of novel quantum materials and spintronic devices.
This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.
11:30 AM - EM02.10.09
Voltage Controlled Magnetic Anisotropy of Ultrathin Fe and Pt Characterized by X-Ray Magnetic Circular Dichroism Spectroscopy
Takuya Tsukahara 1 , Takeshi Kawabe 1 , Koki Shimose 1 , Taishi Furuta 1 , Risa Miyakaze 1 , Kohei Nawaoka 1 , Minori Goto 1 4 , Takayuki Nozaki 3 , Shinji Yuasa 3 , Yoshinori Kotani 2 , Kentaro Toyoki 2 , M. Suzuki 2 , Tetsuya Nakamura 2 , Yoshishige Suzuki 1 4 , Shinji Miwa 1 4
1 Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan, 4 Center for Spintronics Research Network, Osaka University, Toyonaka, Osaka, Japan, 3 Spintronics Research Center, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan, 2 , Japan Synchrotron Radiation Research Institute, Sayo, Hyogo, Japan
Show AbstractIn order to realize magetoresistive random access memory (MRAM), it is important to electrically control magnetization direction in nanomagnets. Aside from current-induced magnetic field and spin-transfer effect, voltage controlled magnetic anisotropy (VCMA) in ferromagnetic metal is a candidate [1]. However, it is necessary to enhance VCMA. The one method to enhance the VCMA is increasing the number of charge-transfer utilizing chemical reaction. For instance, in Co/GdOx system, a huge anisotropy change of 10,000 fJ/Vm has been reported [2, 3]. However, improving a response-speed and a write-duration is challenging. The other is utilizing charge redistribution. For instance, in L10-FePt/MgO system, it has been reported that voltage induction of magnetic dipole moment (Tz term) drastically changes the magnetic anisotropy due to spin-flip term of LS coupling [4]. In the present study, we study the FePt/MgO system in detail by employing Fe(0.5 nm)/Pt(0.2 nm)/MgO multilayer.
We first prepared a tunnel junction with Fe(0.5 nm)/MgO interface by molecular beam epitaxy, and characterized X-ray magnetic circular dichroism (XMCD) at Fe L-edge. We developed our experimental design of fluoresce yield XMCD with a precision 40 times greater than Ref. 5. XMCD of Fe was characterized while external voltages of ±2.6 V (±0.18 V/nm) were applied. As a result, the XMCD change induced by the external voltage was less than 0.2%. Note that no trace of electrochemical reaction was confirmed in Fe/MgO system, and VCMA should be caused by purely electronic effect [6].
Next, we prepared Fe(0.5 nm)/Pt(0.2 nm)/MgO(2 nm) multilayers, which had Pt monoatomic layer inserted at the Fe/MgO interface. XMCD at Pt L-edge under external voltages of ±2.6 V (±0.18 V/nm) was characterized. From magnetization hysteresis, the system shows VCMA of 140 fJ/Vm while that of Fe/MgO was 30 fJ/Vm. Then an extended X-ray absorption fine structure at Pt L3 edge was characterized. As a result, voltage induced lattice relaxation around Pt atom was less than ±1% [7]. Voltage-induced XMCD at Pt L-edge was also characterized and almost reproduced the results of L10-FePt/MgO system [4]. From the present study, note that Pt monatomic layer at the interface with MgO plays an important role for the VCMA in both L10-FePt/MgO and Fe/Pt/MgO systems. Moreover, the VCMA can be strongly correlated to voltage induction of electric quadrupole in Pt. This was not caused by lattice relaxation but by inhomogeneous electric field potential at Pt/MgO.
This work was supported by ImPACT program and JSPS KAKENHI (Nos. JP26103002, JP15H05420).
[1] Y. Shiota et al., Nat. Mater. 11, 39 (2012)
[2] B. Chong, et al., Phys. Rev. Lett. 113, 267202 (2014)
[3] U. Bauer et al., Nat. Mater. 14, 174 (2015)
[4] S. Miwa et al., Nat. Commun. 8, 15848 (2017)
[5] S. Miwa et al., Appl. Phys. Lett. 107, 162402 (2015)
[6] T. Tsukahara et al., Jpn. J. Appl. Phys. 56, 060304 (2017)
[7] M. Suzuki et al., Appl. Phys. Express 10, 063006 (2017)
11:45 AM - EM02.10.10
Piezoelectricity in Semiconducting Layer in Ferroelectric/Semiconductor Oxide Superlattice
Seung Hyun Hwang 1 , Hyeon Jun Lee 1 , Jaesun Song 1 , Hyejeong Lee 1 , Gopinathan Anoop 1 , Sanghan Lee 1 , Ji Young Jo 1
1 , GIST, Gwangju Korea (the Republic of)
Show AbstractSuperlattice thin film consisting of ferroelectric (FE) and non-ferroelectric (non-FE) oxides have been studied for functionality of individual layer different from those of bulk material due to depolarization field arising from discontinuity of polarization. Employing of semiconducting material as non-FE layer into the superlattice with FE layers can provide an opportunity to entangle between spontaneous polarization of FE layer and the unique functionalities of semiconductors such as electroresistance, optical bandgap, and/or photovoltaic behaviors. However, this model has not been investigated experimentally in FE/semiconducting non-FE oxides superlattice. In this study, we have successfully observed the piezoelectricity in semiconducting non-FE layer in the superlattice comprising of BiFeO3 (BFO) as FE oxide and La0.85Ce0.15MnO3 (LCMO) as semiconducting non-FE oxide. The piezoelectric response of individual layers was resolved using time-resolved X-ray microdiffraction experiment under an external electric field and comparing with kinematic diffraction calculation.
A 400 nm-thick BFO/LCMO superlattice thin film with 30 periods of the 29(BFO)/1(LCMO) repeating unit was deposited on a (001)-oriented SrTiO3 (STO) single crystal substrate using pulsed laser deposition. Time resolved X-ray microdiffraction experiment was conducted at the 9C beam line at the Pohang accelerator laboratory. An X-ray beam with energy of 8 keV was focused to a spot with a size of 10 μm onto a circular Pt top electrode with a diameter of 80 μm using a Fresnel zone plate. With an application of electric field, superlattice reflections were shifted to the lower qz values which indicates the piezoelectric expansion. The integrated intensity of superlattice reflections exhibited a small change with application of electric field, indicating that equal piezoelectric response of LCMO layer with that of BFO layer. In order to resolve piezoelectric expansion of semiconducting layer, intensity of superlattice reflection was numerically calculated and then compared with experimental results. Piezoelectric coefficient d33 of LCMO was estimated at approximately 27 pm/V, similar value with d33 of FE BFO layer.
EM02.11: Magnetoelectrics V
Session Chairs
Sakyo Hirose
Margo Staruch
Thursday PM, November 30, 2017
Hynes, Level 1, Room 107
1:30 PM - *EM02.11.01
Material Guidelines for Magneto-Electric Interactions on the Atomic Scale
Alexander Lou 2 , Elizabeth Dreyer 1 , Alexander Fisher 1 , Stephen Rand 1 , Apoorv Shanker 1 , Jinsang Kim 1 , Tobin Marks 2
2 Department of Chemistry and Materials Research Center, Northwestern University, Evanston, Illinois, United States, 1 Center for Dynamic Magneto-Optics, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractIn the past, magneto-electric interactions were analyzed at a macroscopic level and were viewed as complex properties of bulk media. Great effort has been expended on empirical studies to optimize bulk properties for specific applications, but the idea of realizing magneto-electric effects in individual atoms or molecules has remained merely a theoretical possibility. However recent work has shown both theoretically and experimentally that magneto-electric (M-E) response can arise in individual molecules driven jointly by the electric and magnetic fields of light, and can manifest itself either as nonlinear M-E magnetization or as M-E rectification phenomena. There is presently a limited understanding of how structural features of molecular materials impact M-E response. Here we report experimental comparisons of M-E response in a variety of materials to draw conclusions regarding key features of molecular design parameters that mediate strong, atomistic magnetic response. We also identify new relationships between M-E nonlinear coefficients and individual third-order electric susceptibility elements that serve as more general guidelines for M-E materials synthesis to support energy conversion applications.
Light scattering experiments were performed in a 90 degree geometry. Incident light pulses had a nominal duration of 150 fs and peak intensities at a repetition rate of 1 kHz were in the range of 10-1000 MW/cm2. Scattered light was detected in a polarization-sensitive fashion that permitted not only the separation of electric and magnetic dipole scattering but the complete mapping of their radiation patterns. It was therefore possible to record radiation patterns at different values of the incident intensity, confirm their dipolar nature, and to measure the intensity-dependence of magneto-electric response in various samples. Semiconductor-grade transparent liquids were selected for study in a series that varied the molecular moment of inertia systematically while avoiding chirality or polar compositions. More specifically, the series included the group IV tetrachlorides SnCl4, GeCl4, SiCl4, and CCl4. Relative intensities of cross-polarized scattering were then found to follow the proportionality to the transition moment of the first molecular resonance and an inverse dependence on rotation frequency predicted by quantum theory of a 2-photon process driven by E and H components of the driving field.
In addition we have shown that magneto-electric susceptibilities are directly related to two elements of the all-electric third–order susceptibility. M-E magnetization is governed by chi(xxxx) and M-E rectification by chi(zzxx) at the molecular level. This allows us to develop guidelines for synthesizing improved optical M-E materials using valence band theory and other models that are quite specific about desirable bonding structures and elemental composition.
2:00 PM - EM02.11.02
Low Frequency picoTesla Magnetic Field Detection Using Magnetoelectric Composite Based on Delta-E Effect
Menghui Li 1 , Cunzheng Dong 1 , Haomiao Zhou 2 , Zhiguang Wang 1 , Nian Sun 1
1 , Northeastern University, Boston, Massachusetts, United States, 2 , China Jiliang University, Hangzhou, Zhejiang, China
Show AbstractMagnetoelectric (ME) composites have shown their great potential for applications in AC or DC magnetic sensors. When detecting DC magnetic field, an excitation field at low frequency or the electromechanical resonance (EMR) frequency of the ME composite is required. This increase the size of the sensor unit, and might lead to interference with neighboring sensors. Here, we developed sensitive magnetic sensor by metglas/PZT composite, utilizing delta-E effect of metglas. The shift of resonant frequency under DC bias field led to the impedance change of the ME composite. The optimum structure in our composite was found to be different from ME sensor by using direct ME effect. The highest sensitivity was observed under a small bias field near EMR. Our sensor could detect magnetic field as low as 30 pT at 10 Hz and DC field of 100 pT. Higher space resolution could be achieved in ME sensor arrays.
2:15 PM - *EM02.11.03
Structural Evolution and Characteristics of Hexagonal Lu1-xInxFeO3 Multiferroic Ceramics
Xiang Ming Chen 1 , Juan Liu 1 , Xiao Qiang Liu 1
1 , Zhejiang University, Hangzhou China
Show AbstractThe hexagonal rare earth ferrites RFeO3 have attracted the increasing scientific interests as room-temperature multiferroic new candidates. However, at room-temperature, the central symmetric orthorhombic structure is generally stable while the hexagonal phase is only stable under some strict conditions. Therefore, it is the key issue to achieve the stable hexagonal symmetry in RFeO3 for creating room-temperature multiferroic new materials. In the present work, the symmetry of LuFeO3 has been tuned from orthorhombic to hexagonal by In-substitution for Fe. The hexagonal Lu1-xInxFeO3 solid solutions have been obtained for x≥0.4, while the bi-phase structure is determined for x<0.4. The XRD refinement results indicate the structure evolution from noncentrosymmetric P63cm (x=0.4~0.6) to centrosymmetric P63/mmc (x=0.75), and the SAED (selected area electron diffraction) patterns also confirm this structural evolution. Two magnetic transitions have been determined for all compositions: paramagnetic to antiferromagnetic transition at Néel temperature TN, and antiferromagnetic to weak-ferromagnetic transition at spin-reorientation temperature TSR. The spontaneous polarization has been determined by high angle annular dark field (HAADF) image of scanning transmission electron microscopy (STEM).
2:45 PM - EM02.11.04
Impact of Isovalent and Aliovalent Doping on Mechanical Properties of Mixed Phase BiFeO3
Yooun Heo 1 , Songbai Hu 1 , Pankaj Sharma 1 , Kwang-Eun KIm 2 , Byung-Kweon Jang 2 , Claudio Cazorla 1 , Chan-Ho Yang 2 , Jan Seidel 1
1 , UNSW, Sydney, New South Wales, Australia, 2 , KAIST, Daejeon Korea (the Republic of)
Show AbstractThe strain-induced morphotropic phase boundary (MPB) in BiFeO3 has attracted considerable interest to this material as a promising lead-free multiferroic with its pivotal development at the R-T interfaces such as enhanced electromechanical coupling, electrical conduction and strong magnetic moments. For this, strain gradient across the phase boundaries is considered a key factor. Recently, extraordinary soft behaviour has been reported in morphotropic BFO thin films including its correlated functional properties [1, 2]. In this study, we report the effect of doping in BFO thin films on mechanical properties, revealing variations in the elasticity across the competing phases and their boundaries [3]. Spectroscopic force-distance (F-D) curves AFM are used to characterise the structure and elastic properties of three BFO thin film candidates (pure-BFO, Ca-doped BFO, La-doped BFO). First-principles simulation methods are also employed to understand the observed mechanical properties in pure and doped BFO thin films and to provide microscopic insight on them. These results provide key insight into doping as an effective control parameter to tune nanomechanical properties and suggest an alternative framework to control coupled ferroic functionalities at the nanoscale.
[1] Y. Heo, et al., Advanced Materials 26, 7568 (2014).
[2] P.Sharma, et al., Advanced Materials Interfaces 3, 1600033 (2016).
[3] Y. Heo, et al., ACS Nano 11, 2805 (2017)
3:30 PM - *EM02.11.05
Enhancement of Magnetism in Perovskite Ferromagnetic Insulator LaMnO3 via Interface Engineering
Liang Wu 1 , Changjian Li 2 , Mingfeng Chen 1 , Jing Ma 1 , Xiao Wang 3 , Ce-Wen Nan 1
1 , Tsinghua University, Beijing China, 2 , National University of Singapore, Singapore Singapore, 3 , Nanyang Technological University, Singapore Singapore
Show AbstractEngineering ferromagnetism, by modulating its magnitude and anisotropy, is an important topic in the field of magnetism and spintronics. Among different types of engineering of magnetism, of particular interest is the modulating of magnetism in a ferromagnetic insulator (FMI) in which magnetic moment unusually coexist with localized electrons. In this field, the perovskite oxides are supposed to be natural and better choices for their chemical and structural compatibility. However, only a few perovskites have been known as FMIs, and their applications in spintronics are less investigated so far. Recently, a polar discontinuity interface of LaMnO3 (LMO)/SrTiO3 has been designed to trigger ferromagnetism in LMO thin film, indicating the property of an insulating state. In this talk, we validate the FMI behavior in LMO thin films down to a nanometer scale and demonstrate a simple way to enhance the ferromagnetism of LMO through interface engineering, e.g., an abrupt ferromagnetism enhancement in LMO emerges by capping or buffering even a mono-layer LaAlO3. The study demonstrates an effective and dramatic approach to modulate the functionality of ferromagnetic insulators, contributing to the arsenal of engineering techniques for future spintronics.
4:00 PM - EM02.11.06
Phase Field Modeling of Strain-Mediated Magnetoelectric Coupling in Multiferroic Composite Films Enhanced by Patterned Interfaces
Youness Alvandi-Tabrizi 1 , Justin Schwartz 1
1 Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina, United States
Show AbstractThe interfacial connectivity between the constituents plays a crucial role in the effectiveness of the strain-mediated magnetoelectric (ME) coupling in composite films. Two common approaches are multilayered thin films and nano-pillars embedded in a film matrix; each has advantages and challenges. On one hand, the in-plane strain coupling in layered structure is impacted by the constraint imposed by the substrate. On the other hand, the vertical interfaces of the nano-pillars span the entire thickness of the film, resulting in current leakage problems. Since the out-of-plane strain coupling is not affected by substrate clamping, one could expect the highest ME coupling for the vertical interfaces if the leakage problem is resolved. An ideal system for achieving high ME coupling through strain thereby would be one containing vertical interfaces that are not continuous in the field direction. To achieve this, a new design principle based on patterned interfaces is proposed. The patterning introduces three-dimensional interfaces, some of which are vertical, consistent with the ideal geometry for ME coupling, while the layered structure also eliminates the current leakage problem.
A three-dimensional meso-scale model based on the phase-field approach is developed and implemented in COMSOL Multiphysics to study the efficacy of the new design for improving strain-mediated ME coupling. The model employs an expression of free energy functional that relates magnetic moments and dielectric polarization to mechanical strain, magnetic field, and electric field. The Landau–Lifshitz–Gilbert and time-dependent Ginzburg-Landau equations are used to minimize the free energy functional and predict the temporal and spatial evolution of the magnetic moments and dielectric polarizations. Both equations fall into the category of Allen-Cahn type equations that are successfully used in phase-field methods for predicting the evolution of non-conserved fields. The model accounts for the substrate induced strain, crystallographic orientations, and polycrystallinity of the phases. It also takes the advantage of solving all equations simultaneously while using different discretization for each one of them to lower the computational cost.
The results for barium titanate and cobalt ferrite composite films indicate that patterned interfaces substantially enhance ME coupling. The converse ME effect (voltage control of magnetization) shows a much stronger effect than the direct ME effect (magnetic control of dielectric polarization).
4:15 PM - EM02.11.07
Ion-Gel-Gating Control of Magnetism on Flexible Polyimide Substrates
Hongjia Zhang 1 , Ziyao Zhou 1 , Xinger Zhao 1 , Le Zhang 1 , Xu Xue 1 , Shishun Zhao 1 , Ming Liu 1
1 , Xi'an Jiaotong University, Xi'an China
Show AbstractIn spite of recent rapid development of electronic systems on flexible substrate including integrated circuits, sensors and organic transistors [1-3], the research towards nonvolatile flexible memory is still a significant challenge. The past work focused primarily on field effect transistors with solid substrates, controlling the spin degree and magnetic states of materials and providing a new pathway to achieving novel memory [4].
To realize this flexible spintronics, the Pt (0.9 nm)/Fe (2 nm) ultra-thin films heterostructure is fabricated onto flexible polyimide substrates. After that, a network-forming polymer and a room temperature ionic liquid are combined to synthesize ion gel [5]. The modulation of magnetic anisotropy by applied gating voltage (Vg) across the ion gel is detected by in situ vibrating sample magnetometer (VSM) and electron spin resonance measurements (EPR). Here we demonstrate voltage control of magnetic anisotropy (VCMA) of the heterostructure via a circuit Vg (1.8 V). A reversible, non-volatile VCMA switching of about 100 Oe has been achieved. The similar tunable results of EPR is obtained while the substrates are under bending condition, proving the reliability and adaptability of IL gel gating control of flexible spintronics. Our work is the first demonstration of VCMA on flexible substrates and it is promising for next generation robust, flexible, low voltage tunable, non-volatile spintronics such as memories, sensors and logical devices.
Reference
1. Rogers, J.A., et al., Materials and Mechanics for Stretchable Electronics. Science. 2010, 327, 1603-1607.
2. Mcalpine, M.C., et al., Highly ordered nanowire arrays on plastic substrates for ultrasensitive flexible chemical sensors. Nature Materials. 2007, 6, 379–384.
3. Gelinck, G.H., et al., Flexible active-matrix displays and shift registers based on solution-processed organic transistors. Nature Materials. 2004, 3, 106–110
4. Liu, M., et al., Voltage Tuning of Ferromagnetic Resonance with Bistable Magnetization Switching in Energy-Efficient Magnetoelectric Composites. Adv. Mater. 2013, 25, 1435–1439
5. Lee, K.H., et al., “Cut and Stick” Rubbery Ion Gels as High Capacitance Gate Dielectrics. Adv. Mater. 2012, 24, 4457–4462
4:30 PM - EM02.11.08
Phase-Field Model of Ferroelectric Domain Dynamics under Ultrafast Stimuli
Tiannan Yang 1 , Zijian Hong 1 , Jiamian Hu 1 , Hirofumi Akamatsu 1 , Venkatraman Gopalan 1 , Long-Qing Chen 1
1 , Pennsylvania State Univ, University Park, Pennsylvania, United States
Show AbstractApplying an ultrafast stimulus to a ferroelectric material allows one to explore possible new transient phenomena or new metastable domain patterns that may emerge during the relaxation from its excited state to its original or a new equilibrium state. In this work, we develop a phase-field model for understanding and predicting the dynamical responses of both ferroelectric and ferroelastic domain patterns under ultrafast electric and mechanical stimuli. As an example, we studied the nanoscale domain dynamics of barium titanate crystals under high frequency stimuli. We successfully explained the experimentally observed phenomena with distinct responses determined by both the orientation and the location of the domains. Mesoscale mechanisms of ferroelectric domain and domain wall responses as well as intrinsic lattice vibrations are revealed. The theoretical insights on ultrafast domain dynamics will provide useful guidance for manipulating the dynamic functionalities of ferroelectric materials.
4:45 PM - EM02.11.09
Embedded Sensing of Damage in a Carbon Fiber Reinforce Polymer Using Magnetostrictive Particles
Asha Hall 1 , Michael Coatney 1 , Mulugeta Haile 1 , Jin Yoo 2
1 , U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland, United States, 2 Physical Metallurgy, Naval Surface Warfare Center, Bethesda, Maryland, United States
Show AbstractThe integrity of composite structures gradually degrades due to the onset of damage such as matrix cracking, fiber/matrix debonding, and delamination. Over the last two decades, great strides have been made in structural health monitoring (SHM) community using various sensing techniques such as acoustic emission, eddy current, strain gages, etc., to diagnose damage in aerospace, mechanical and civil infrastructures. Embedded sensing offers the prospects of proving for real-time, in-service monitoring of damage were weight savings is a major factor in Aerospace Industry. It also provides for a new paradigm in providing early stage damage detection in materials and structures through the integration of stimuli responsive approach to provide local indicators of a change of the materials properties. In this present work, magnetostrictive particles such as Terfenol-D were embedded in a composite structure, along with multiple SHM techniques, to capture the damage in an IM7-carbon fiber reinforced polymer composite system undergoing fatigue loading. As the internal stress state increases, the change in the magnetization flux intensity was captured using a non-contact magnetic field sensor. A damage diagnosis system was established along with an acoustic emissions technique to further validate the damage captured by the embedded system. Magnetization of the sample from before and after stress cycle test will be evaluated for verifying the stress effect on the magnetic status. It was confirmed through numerous tests that a change in materials properties served as an indicator of early stage damage detection.
Symposium Organizers
Nian Sun, Northeastern University
Franz Faupel, Kiel University
Cewen Nan, Tsinghua University
Ramamoorthy Ramesh, University of California, Berkeley
EM02.12: Magnetoelectrics VI
Session Chairs
Kevin Geishendorf
Yuyi Wei
Friday AM, December 01, 2017
Hynes, Level 1, Room 107
8:00 AM - EM02.12.01
Ferroelectricity, Antiferroelectricity and Ultrathin 2D Electron/Hole Gas in Multifunctional Monolayer MXene
Anand Chandrasekaran 1 , Avanish Mishra 1 , Abhishek Singh 1
1 Materials Research Centre, Indian Institute of Science Bangalore, Bengaluru, KA, India
Show AbstractFerroelectric materials are of great technological importance and have also been subject to intense fundamental studies due to their multifaceted properties. In general, perovskite oxides have been the prime focus in the ferroelectrics field over the past few decades and materials such as PZT (lead zirconate titanate) have been utilized recently in nonvolatile memory applications (FeRAM). However, the ferroelectric properties of these materials disappear at the nanoscale due to a depolarizing field at the surface. We reported for the first time a monolayer of a 2-dimensional material oxygen-functionalized MXene (Sc2CO2), which possesses both ferroelectric and antiferroelectric low-energy configurations. By applying an electric field, one may switch from one ferroelectric configuration to another. The switching of polarization in this new class of ferroelectric materials occurs through a previously unknown intermediate antiferroelectric structure, with energy barrier for switching is sufficiently high to ensure the presence of three distinct states (+Pz, 0, −Pz) for nonvolatile memory applications even at room temperature. The so-called “domain-walls” in these materials are conductive in nature and act as atomic-scale charge transport pathways. Another interesting aspect of this material is the transition from insulator to a nondegenerate 2-dimensional electron gas system as we go from the monolayer to bilayer. The 2DEG is nondegenerate due to spin−orbit coupling, thus paving the way for spin−orbitronic devices. Usually the formation of a 2DEG in complex oxides requires careful preparation using molecular beam epitaxy, whereas in our case it can be produced by the simple stacking of polar 2D materials. The band gap of Sc2CO2 as revealed by the HSE06 calculations (2.92 eV) is within the visible spectra range. In the case of multilayer Sc2CO2, light which is incident on the insulating bulk of the material will result in the absorption of a photon and the creation of an electron−hole pair. However, due to the in-built electric field, the electron and hole are separated and transported to opposite surfaces of the multilayer which are conductive in nature. This material is thus an ideal candidate for novel polarization-driven photovoltaic devices that have been proposed very recently. The plethora of properties shown by this single material will very likely spur intense experimental and theoretical investigation in the direction of polar 2-D materials.
8:15 AM - EM02.12.02
Transparent Flexible Piezoelectric Thin Film for MEMS Based on van der Waals Heteroepitaxy
Chun-Hao Ma 1 2 , Po-Wen Chiu 1 , Ying-Hao Chu 2
1 Department of Electrical Engineering, National Tsing Hua University, Hsinchu Taiwan, 2 Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu Taiwan
Show AbstractOver the past decades, a quick rise of the Internet of Things is changing our daily life. Transparent flexible microelectromechanical systems (MEMS) with active piezoelectric layers offering integrated sensing, actuation and transduction are desirable for future portable and wearable devices in smart electronic applications. However, no reliable method to directly fabricate transparent flexible piezoelectric systems exists yet. As a promising technology for transparent flexible piezoelectric applications, we present a direct fabrication of transparent epitaxial lead lanthanum zirconate titanate (PLZT) on flexible mica substrate via van der Waals epitaxy. These single-crystalline transparent flexible piezoelectric PLZT films not only retain their performance, reliability, and thermal stability comparable to those on rigid counterparts but also exhibit remarkable mechanical properties. This study marks the technological advancement towards the realization of transparent flexible piezoelectric heterostructures for the design and development of next-generation smart devices with potential applications in ultrasound medical imaging, microfluidic control, mechanical sensing, and energy harvesting.
8:30 AM - *EM02.12.03
Voltage Control of Interfacial Magnetic Anisotropy, Dzyaloshinskii-Moriya Interaction and Exchange Coupling in Fe/MgO-Based Artificial Multilayers
Shinji Miwa 1 7 , Kohei Nawaoka 1 , Jaehun Cho 1 , Takayuki Nozaki 2 , M. Suzuki 3 , Masahito Tsujikawa 4 8 , Takuya Tsukahara 1 , Minori Goto 1 7 , Frederic Bonell 1 , Eiiti Tamura 1 , Hitoshi Kubota 2 , Shingo Tamaru 2 , Kay Yakushiji 2 , Akio Fukushima 2 , Yoshinori Kotani 3 , Tetsuya Nakamura 3 , Masafumi Shirai 4 8 , Tadakatsu Ohkubo 5 , Kazuhiro Hono 5 , Chun-Yeol You 6 , Shinji Yuasa 2 , Yoshishige Suzuki 1 2 7
1 Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan, 7 Center for Spintronics Research Network (CSRN), Osaka University, Toyonaka, Osaka, Japan, 2 Spintronics Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan, 3 , Japan Synchrotron Radiation Research Institute (JASRI), Sayo, Hyogo, Japan, 4 Research Institute of Electrical Communication, Tohoku University, Sendai, Miyagi, Japan, 8 Center for Spintronics Research Network (CSRN), Tohoku University, Sendai, Miyagi, Japan, 5 Research Center for Magnetic and Spintronic Materials, National Institute for Materials Science (NIMS), Tsukuba, Ibaraki, Japan, 6 Department of Emerging Materials Science, DGIST, Dalseong, Daegu, Korea (the Republic of)
Show AbstractSpin-transfer torque has surpassed current-induced magnetic fields as the preferred technology for switching magnetization directions in nanoscale magnets because of its low energy consumption and excellent scalability. However, spin-transfer switching exhibits Joule heating that remains too large to ignore. The energy required for magnetization switching is more than 107 times the Landauer limit of kBTln2. Thus, a novel method offering magnetization control without electric current is highly desirable. Voltage-controlled magnetic anisotropy (VCMA) in Fe|MgO-based tunnel junctions [1] has shown that magnetization of nanomagnets can be controlled in fast periods (down to 0.1 ns) by electric fields, as indicated by bi-stable precessional magnetization switching [2], and ferromagnetic resonance excitation [3,4]. Because the VCMA mechanism can be purely electronic, this is an ultimate technology for the operation of spintronics devices, such as nonvolatile random access memory, where high-speed operation with high writing endurance is indispensable.
In this talk, we will show our recent studies on voltage control of interfacial magnetic anisotropy, Dzyaloshinskii-Moriya interactioin, and exchange coupling. For VCMA, we show a new mechanism to enhance VCMA in Fe/Pt/MgO tunnel junction proved by X-ray absorption spectroscopy and first principles study. Electric field at metal/dielectric interface couples not only with an electric dipole but also a quadrupole of an electron shell in a metal layer. The induced electric quadrupole produces the intra-atomic magnetic dipole term (Tz) and influences magnetic anisotropy through spin-flip excitation [5]. Our finding enables the design of novel materials showing VCMA larger by more than a factor of 10. For voltage control of interfacial DMI, we show a voltage induction of large DMI in Fe/Pt/MgO multilayer, which is enough to stabilize and un-stabilize the skyrmion [6]. Moreover, we have recently established the technique to separately characterize voltage control of anisotropy, magnetization and exchange stiffness by spin-wave spectroscopy in magnetic tunnel junction. We will show how an external voltage influences the exchange stiffness constant in FeCoB/MgO tunnel junction [7].
This work was supported by the ImPACT Program of the Council for Science, Technology and Innovation. (Cabinet Office, Government of Japan), and also supported by JSPS KAKENHI (Nos. JP26103002 and 15H05420).
[1] T. Maruyama et al., Nat. Nanotechnol. 4, 158 (2009).
[2] Y. Shiota et al., Nat. Mater. 11,.39 (2012).
[3] T. Nozaki, SM et al., Nat. Phys. 8, 491 (2012).
[4] J. Zhu et al., Phys. Rev. Lett. 108, 197203 (2012).
[5] S. Miwa et al., Nat. Commun. 8, 15848 (2017).; M. Suzuki, SM et al., Appl. Phys. Express 10, 063006 (2017).
[6] K. Nawaoka, SM, et al., Appl. Phys. Express 8, 063004 (2015).; K. Nawaoka, SM, et al., submitted.
[7] J. Cho, SM et al., Phys. Rev. B 94, 184411 (2016).; J. Cho, SM et al., submitted.
9:00 AM - EM02.12.04
Nanoscale Imaging of Elastic Domain Walls in Fe-Ga Magnetic Alloys
Weibing Yang 1 , Ravini Chandrasena 1 , Marcus Forst 1 2 , James Boligitz 1 , Arian Arab 1 , Martin Holt 3 , Andreas Scholl 4 , Elke Arenholz 4 , Hubert Ebert 5 , Jan Minar 6 , Thomas Lograsso 7 8 , Harsh Chopra 2 , Alexander Gray 1
1 Department of Physics, Temple University, Philadelphia, Pennsylvania, United States, 2 Mechanical Engineering Department, Temple University, Philadelphia, Pennsylvania, United States, 3 Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois, United States, 4 Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 5 Department Chemie, Ludwig-Maximilians-Universität München, München Germany, 6 New Technologies Research Center, University of West Bohemia, Pilsen Czechia, 7 Division of Materials Science and Engineering, AMES Laboratory, Ames, Iowa, United States, 8 Department of Materials Science and Engineering, Iowa State University, Ames, Iowa, United States
Show AbstractHere we present the results of our recent investigations of non-Joulian magnetostrictive Fe-Ga alloys using a combination of nanoscale scanning x-ray diffraction microscopy and high-resolution polarization-dependent photoelectron microscopy. We show that an overwhelming volume of the crystal is occupied by long-wavelength (~270 nm) elastic domain walls, with domains as the narrow transition regions. It is found that the gradients inside the wall are accommodated by gradually increasing/decreasing inter-planar lattice spacing resembling a longitudinal wave. The magnetic structure modulates with a similar periodicity (~255 nm) and the resulting correspondence of these periodicities produces ‘giant’ magnetic-field-induced deformation equal to the self-strain of an elastic wall. The hallmark of this new type of ferroics is hysteresis-free, reversible actuation.
9:15 AM - *EM02.12.05
Electric-Field Control of Magnetism in Multiferroic Heterostructures
Yonggang Zhao 1
1 Department of Physics, Tsinghua University, Beijing China
Show Abstract
With the fast development of information storage, exploiting new concepts for dense, fast, and non-volatile random access memory with reduced energy consumption is a significant and challenging task. To realize this goal, electric-field control of magnetism is crucial. In this regard, multiferroic materials are important and have attracted much attention due to their interesting new physics and potentials for exploring novel multifunctional devices [1, 2]. In the multiferroic materials, electric polarization can be tuned by applying an external magnetic field or vice versa. This magnetoelectric (ME) effect originates from the coupling of the magnetic and ferroelectric orders. However, single-phase multiferroic materials are rare and the multiferroic heterostructures, composed of ferromagnetic (FM) and ferroelectric (FE) materials, provide an alternative way for exploring the ME coupling effect. One of the key issues in the study of the FM/FE heterostructures is the control of magnetism via electric fields, which is essential for the new generation information storage technology. We have combined ferroelectric Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (PMNT) with different materials and studied the electric-field control of magnetic and electronic transport properties of thin films grown and magnetic tunnel junctions grown on PMNT [3]. In this talk, I’ll present our recent progress in electric-field control of magnetism in magnetic thin films, multilayers and small islands grown on PMNT, involving some interesting behaviors as revealed by both macroscopic and spatially-resolved techniques [4]. Our work demonstrates the interesting new physics and potential applications of electric-field control of magnetism in multiferroic heterostructures.
References
1. W. Eerenstein, N. D. Mathur, and J. F. Scott, Nature 442,759 (2006).
2. R. Ramesh and N. A. Spaldin, Nature Mater. 6, 21 (2007).
3. S. Zhang et al., Phys. Rev. Lett. 108, 137203 (2012); S. Zhang et al., Scientific Reports 4, 3727 (2014); L. F. Yang et al., Scientific Reports 4, 4591 (2014); P. S. Li et al., Adv. Mater. 46, 2340 (2014); Z. Lin et al., Scientific Reports 5, 14133 (2015).
4. A. T. Chen et al., Adv. Mater. 28, 363 (2016); Y. Liu et al., ACS Appl. Mater. Interfaces 8, 3784 (2016); P. S. Li et al., ACS Appl. Mater. Interfaces, 9, 2642 (2017). Y. Sun et al., ACS Appl. Mater. Interfaces, 9, 10855(2017); B. You et al., to be submitted.
9:45 AM - EM02.12.06
Mottronics in Magnetic Domain Walls
Saeedeh Farokhipoor 2 1 , David Pesquera 2 , Massimo Ghidini 2 , Jing Wang 2 , Xavier Moya 2 , Francesco Maccherozzi 3 , Sarnjeet Dhesi 3 , Neil Mathur 2
2 Material Science, University of Cambridge, Cambridge United Kingdom, 1 , University of Groningen, Geroningen Netherlands, 3 , Diamond Light Source, Oxford United Kingdom
Show AbstractDomain walls (DWs) in complex oxides have attracted much interest in recent years due to the novel phenomena with which they are associated [1]. The magnetic DWs in mixed-valence manganites with different chemical compositions (and thus variable electron-lattice coupling) have been investigated, as the magnetic DWs in these manganites possess a large electrical resistance due to phase separation at the DW centres [2]. In this work, the creation and destruction of DW arrays in lithographically designed manganite tracks with contact pads at each end has been studied. The DWs have been manipulated magnetically rather than electrically. Photoemission electron microscopy with x-ray magnetic circular dichroism contrast (XMCD-PEEM) is employed to image the resulting magnetic changes while measuring the concomitant changes in track resistance. By combining the magnetoresistance measurements with the magnetic contrast images obtained using XMCD-PEEM, the DW resistance-area product for a range of DW compositions can reliably be quantified, in contrast with studies with no magnetic imaging [3-5]. This study falls into the category of reconfigurable nanopatterning [6], and the formation of insulating regions in a metallic background can be exploited in Mottronic devices for next-generation memory units and transistors with reduced energy consumption.
[1] S. Farokhipoor et al., Nature 515 (2014) 379.
[2] N. D. Mathur and P. B. Littlewood, Solid State Commun. 119 (2001) 271.
[3] N. D. Mathur et al., J. Appl. Phys. 86 (1999) 6287.
[4] J. Wolfman et al., J. Appl. Phys. 89 (2001) 6955.
[5] T. Arnal et al., Phys. Rev. B. 75 (2007) 220409.
[6] Neil Mathur and Peter Littlewood, Nat. Mater. 3 (2004) 207.
10:30 AM - *EM02.12.07
Design of Strain-Mediated Electrical Control of Non-Collinear Magnetism in Magnetoelectric Heterostructures by Phase-Field Simulations
Jiamian Hu 1 , Tiannan Yang 1 , Long-Qing Chen 1
1 , The Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractElectric field control of non-collinear magnetism represents an emerging topic in the field of multiferroics and magnetoelectrics. It is not only fundamentally interesting but also may lead to new concepts of low-power magnetic and spintronic devices. Computational studies on this topic, however, have remained scarce. In this talk, I will present our recent computational predictions on achieving the strain-mediated electrical control of non-collinear magnetism in magnetic/piezoelectric heterostructures. Examples include controlling the motion of magnetic domain-walls and the switching of magnetic skyrmions. In the former example, a fast (up to 550 m/s) and low-power (as low as 0.2 fJ) magnetic domain wall motion is computationally demonstrated in a magnetic nanoring. In the latter example, we demonstrated, for the first time, a non-volatile and repeatable switching between a non-collinear magnetic skyrmion and an almost uniform magnetization in a magnetic nanodisk. Both the nanoring and the nanodisk are on top of piezoelectric materials. Both designs are demonstrated by performing micromagnetic phase-field simulations through our newly released phase-field-based software package μ-Pro® Mag.
11:00 AM - EM02.12.08
Direct Observation of 'Ferroelectric-Like' Domain Structures in a Polar Metal
Shiming Lei 1 , Mingqiang Gu 2 , Danilo Puggioni 2 , Greg Stone 1 , Jin Peng 3 , Yakun Yuan 1 , Ke Wang 1 , Zhiqiang Mao 3 , James Rondinelli 2 , Venkatraman Gopalan 1
1 , The Pennsylvania State University, University Park, Pennsylvania, United States, 2 , Northwestern University, Evanston, Illinois, United States, 3 , Tulane University, New Orleans, Louisiana, United States
Show AbstractThe possible coexistence of polarity and metallicity in one material system has recently attracted intensive interest. It is not conclusive until recent observation that LiOsO3 undergoes a ferroelectric-like structural phase transition (inversion symmetry breaking) while the metallicity is maintained. The polar nature is uncommon since the conducting electrons are expected to screen out the long-range Coulomb interaction that favors the dipole-dipole cooperative ordering, thus against the formations of polar domains in a metal system. While domains/domain walls are important in the applications of ferroelectrics, their existence in a polar metal system are not clear; no observations were reported so far. Here by a combination of meso-scale optical second harmonic generation (SHG) imaging and atomic-scale high resolution scanning transmission electron microscopy (STEM), for the first time we achieve a direct observation of the polar domains in a polar metal Ca3Ru2O7 system, unveiling the existence of 90° “ferroelastic” and 180° “ferroelectric” domain twinnings. The hybrid improper mechanism, which has been proved to be a robust designing rule for high-temperature ferroelectrics and multiferroics, is found to be responsible for the observed complex domain structures in this polar metal. Using nonlinear optics as a sensitive tool, we also demonstrated the unique nonlinear property change across the isostructural polar transition in Ca3Ru2O7, which is found to be closely coupled to its polar mode instablility. The structural and chemical contributions to the nonlinear properties are discussed and compared to its isostructural ferroelectrics Ca3Ti2O7
11:15 AM - *EM02.12.09
Deterministic Reversal of Magnetic Vortex Circulation by an Electric Field
Jinxing Zhang 1
1 , Beijing Normal University, Beijing China
Show AbstractControl of magnetic vortex textures is highly desirable due to their potential applications in spintronic devices. Traditional methods including magnetic field, spin-polarized current etc. have been used to flip the vortex core and/or circulation. However, electric-field switching of the vortex textures with low-energy consumption is challenging in that such a spin structure has time-reversal broken symmetry and no planar magnetic anisotropy. Here, we report that a deterministic reversal of magnetic vortex circulation can be driven by a space- and time-varying strain in multiferroic heterostructures, which is controlled by using a bi-axial electric field. Phase-field simulation reveals the mechanism of the emerging magnetoelastic energy with the space/time variation and visualizes the switching pathway of the vortex. The reversible electric-field switching of the magnetic vortex circulation demonstrates a new approach to integrate the low-dimensional spin texture into the magnetoelectric thin film devices with low energy consumption.
11:45 AM - EM02.12.10
Weak Ferromagnetism from Magnetic Soliton in a Polar Ruthenate for Magnetoelectric Coupling
Shiming Lei 1 , Venkatraman Gopalan 1 , Jin Peng 4 , Zhiqiang Mao 4 , Shalinee Chikara 2 , Franziska Weickert 2 , Marcelo Jaime 2 , John Singleton 2 , Vivien Zapf 2 , Mengze Zhu 3 , Xianglin Ke 3 , Weiwei Zhao 1 , Mingqiang Gu 5 , Danilo Puggioni 5 , James Rondinelli 5
1 , The Pennsylvania State University, University Park, Pennsylvania, United States, 4 , Tulane University, New Orleans, Louisiana, United States, 2 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 3 , Michigan State University, East Lansing, Michigan, United States, 5 , Northwestern University, Evanston, Illinois, United States
Show AbstractMagnetoelectric (ME) effect describes the coupling between magnetic ordering and ferroelectricity, which provides good opportunities to achieve control of ferroelectric polarization by magnetic field, and control of magnetism by electric field, and eventually towards multifunctional devices1. ME coupling has been studied intensively in multiferroic materials, which is characterized by the coexistence of at least two simultaneous long-range orders such as (anti)ferromagnetism, ferroelectricity, and ferroelasticity.
Two types of multiferroics(MFs) have been under intensive study and they exhibit quite distinstive feature. In type I MFs, the ferroelectricity occurs regardless of magnetism due to their different origins, thus leading to relatively weak magnetoelectric coupling. In comparison, in Type II MFs the inversion symmetry breaking originates from magnetic orders, therefore it is also called spin-driven ferroelectricity. Due to its intimate coupling between ferroelectricity and magnetic order, a large ME effect is expected. Therefore, Type I and Type II MFs exhibit quite distinctive features. It is worthwhile to emphasize that the ferroelectric order can be proper or improper in Type I MFs. The recent proposed hybrid improper mechanism belongs to the latter case, where the inversion-symmetry breaking is unlocked by a combination of two nonpolar octahedron rotation modes of different symmetry, X2+ and X3-, thus it was termed as hybrid improper ferroelecticity. Since these octahedron rotation modes strongly couples electronic (spin and orbital) degrees of freedom, a weak ferromagnetism with linear ME effect could exist.
Here by providing a compressive experiment results from transport, second harmonic generation (SHG), neutron diffraction and magnetization, we report a material system in which the polar order comes from the hybrid improper mechanism, while the weak ferromagnetism comes from the metastable incommensurate structure. Importantly, we found a direct coupling between the polar displacement and the magnetic order from our magnetoelastic measurements. We further provide a microscopic spin model for understanding on the existence of the metastable phase and how the weak ferromagnetism develops.