Symposium Organizers
John Heron, University of Michigan
Satoshi Okamoto, Oak Ridge National Laboratory
Morgan Trassin, ETH Zürich
Pu Yu, Tsinghua University
Symposium Support
CrysTec Gmbh
Lake Shore Cryotronics Inc
NT-MDT America Inc.
Radiant Technologies, Inc
Twente Solid State Technology B.V.
ES10.1: Complex Oxides—Ferroelectric Domains and Domain Walls
Session Chairs
Julia Mundy
Morgan Trassin
Tuesday PM, April 18, 2017
PCC North, 200 Level, Room 222 A
11:30 AM - ES10.1.01
Domain Wall Architecture in Tetragonal Ferroelectric Thin Films
Gabriele De Luca 1 , Marta Rossell 2 , Jakob Schaab 1 , Natalie Viart 3 , Manfred Fiebig 1 , Morgan Trassin 1
1 Department of Materials, ETH Zurich, Zürich Switzerland, 2 Electron Microscopy Center, Empa, Dübendorf Switzerland, 3 , Institut de Physique et Chimie des Matériaux de Strasbourg, Strasbourg France
Show AbstractThe concept of functional oxide interfaces was fundamentally expanded by including domain walls, two-dimensional objects separating regions with a different orientation of the magnetic or electric order. These walls carry properties that do not exist in the bulk because of the resulting lowering of the local symmetry. Additionally they remain mobile after growth and external fields nucleate and annihilate them at will thus rendering them attractive for potential applications. The interplay of electrostatic, chemical, topological, and distortive inhomogeneities at the ferroelectric domain walls can be so complex, however, that this obstructs their technological performance.
In PbZrxTi1-xO3, for example in the context of ferroelectric memories, the desired out-of-plane-polarized c-domains are interspersed by in-plane-polarized a-domains that have to be avoided when 180° domain wall motion is aimed for. Indeed, the 90° domain walls of a-domains originating at surface dislocations are pinned and their immobility obstructs the controlled migration of 180° domain walls. Hence, for devices based on domain-wall motion in tetragonal ferroelectrics, understanding and controlling the distribution and morphologies of a- and c-domains is essential.
Combining scanning transmission electron microscopy and nonlinear optics we determine the relation between strain, film thickness, local electric fields and the resulting domain and domain-wall structure across the entire thickness of various PbZr0.2Ti0.8O3 films. We find that the voltage-induced c-domain walls are inclined and exhibit a mixed Ising-Néel-type rotation of polarization across the wall with a specific nonlinear optical response. The domain wall tilt leads to a macroscopic tail-to-tail polarization component with an expected accumulation of screening charges. The additional understanding of domain walls and their control thus acquired opens new avenues towards the investigation of the dynamics of such nano-scale conduction elements and their future use in nanoelectronic device building blocks.
11:45 AM - ES10.1.02
Emergent Chirality in Electrically Polar Vortex Superlattices
Padraic Shafer 1 , Pablo Garcia-Fernandez 2 , Pablo Aguado-Puente 3 , Anoop Rama Damodaran 4 , Ajay Yadav 5 , Christopher Nelson 4 6 , Shang-Lin Hsu 4 6 , Jacek Wojdel 7 , Jorge Iniguez 8 , Lane Martin 4 9 , Elke Arenholz 1 4 , Javier Junquera 2 , Ramamoorthy Ramesh 4 9 10
1 Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 2 Departamento de Ciencias de la Tierra y Física de la Materia Condensada, Universidad de Cantabria, Santander, Cantabria, Spain, 3 Centro de Física de Materiales, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 4 Department of Materials Science & Engineering, University of California, Berkeley, California, United States, 5 Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California, United States, 6 National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 7 , Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Bellaterra Spain, 8 Materials Research and Technology Department, Luxembourg Institute of Science and Technology (LIST), L-4362 Esch/Alzette Luxembourg, 9 Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 10 Energy Technologies, Lawrence Berkeley National Lab, Berkeley, California, United States
Show AbstractChiral interactions in complex oxides lead to exotic electronic and magnetic textures, such as cycloidal spin structures that couple to ferroelectric polarization, toroidal moment arrangements, chiral domain walls and skyrmions, and orbital currents. However, little is known about the possibility of chirality in complex dielectric or ferroelectric orders in which magnetic interactions are weak or absent. The so-called “polar vortices” in PbTiO3-SrTiO3 superlattices exhibit curled regions of ferroelectric polarization in the PbTiO3 layers that are stabilized by interfacial interactions and boundary conditions at the SrTiO3 interfaces [1]. Pairs of clockwise and counter-clockwise “vortex tubes”—having cross-sections with continuously rotating electric polarization—form as highly ordered arrays both laterally and out-of-plane. We leveraged this high degree of order to perform diffraction experiments investigating the complex structure of the polar vortex arrays and long-range chiral interactions.
Resonant soft x-ray diffraction studies of the PbTiO3-SrTiO3 superlattices reveal diffraction peaks from the vortex arrays that exhibit strong x-ray circular dichroism (XCD) near the titanium L3 resonance. The origin of these peaks is attributed to the anisotropic dielectric susceptibility [2] of the Ti ions enhancing sensitivity to changes in the local electronic environment, such as rotation of the TiO6 octahedra. Theoretical [3] and experimental [4] reports show that such rotations can lead to XCD in chiral crystals, and are consistent with the signature of XCD we observe in PbTiO3-SrTiO3—anti-symmetric with respect to the lateral direction. Ab initio calculations of the vortex arrays suggest that the chiral XCD signal may be linked to an additional axial component of electric polarization. Chirality in such a polar structure is intriguing, especially when coupled to other functional materials that produce new pathways for multiferroic interactions.
References
1. A. K. Yadav et al., Nature 530, 198 (2016).
2. D. H. Templeton & L. K. Templeton, Acta Cryst A 38, 62-67 (1982).
3. V. E. Dmitrienko, Acta Cryst. A 39, 29 (1983).
4. J.-I. Igarashi and M. Takahashi, Phys. Rev. B 86, 104116 (2012).
12:00 PM - *ES10.1.03
Imaging Complex Oxides with Electrons and Photons on Nano- to Picometer Length Scales
Venkatraman Gopalan 1 , Yakun Yuan 1 , Shiming Lei 1 , Greg Stone 1 , Hua Zhou 2 , Nasim Alem 1 , Turan Birol 3 , Darrell Schlom 4 , Bernd Kabius 1 , Colin Ophus 5 , Jim Ciston 5 , Zhiqiang Mao 6
1 , Pennsylvania State University, University Park, Pennsylvania, United States, 2 , Argonne National Laboratory, Argonne, Illinois, United States, 3 , University of Minnesota, Minneapolis, Minnesota, United States, 4 , Cornell University, Ithaca, New York, United States, 5 , Lawrence Berkeley Laboratory, Berkeley, California, United States, 6 , Tulane University, Tulane, Louisiana, United States
Show AbstractWith recent advances in Transmssion Electron Microscopy, Coherent Xray diffraction techniques, and Nonlinear Optical imaging, one can gather unprecedented insights into a wide range of materials. This talk will present examples of the structure of ferroelectric domain walls in ferroelectrics, multiferroics, and correlated oxides using these techniques. Three examples will be presented: First, Competing polar phases in layered ferroelectrics, where structure down to 5pm is quantitatively measured using scanning transmission electron microscopy, and an exceptional agreement is shown with density functional theory. Secondly, a three dimensional reconstruction of the atomic positions and the electronic density of a low symmetry oxide interface is shown with coherent xray techniques. Third, a combination of nonlinear optics and electron microscopy is used to probe domain walls in a polar metal.
12:30 PM - ES10.1.04
Unravelling Elastic Anomalies during Morphotropic Phase Transitions
Pankaj Sharma 1 , Kyungrok Kang 2 , Byung-Kweon Jang 2 , Chan-Ho Yang 2 3 , Jan Seidel 1
1 , The University of New South Wales, Sydney, New South Wales, Australia, 2 , Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of), 3 , Institute for the NanoCentury, KAIST, Daejeon Korea (the Republic of)
Show AbstractIn science, some of the most unique physical phenomena, anomalies and enhancements in the functional physical properties occur at or near the structural phase transformations. The structural phase transformation driven enhanced piezoelectricity at morphotropic phase boundaries (MPB’s) is a prominent example of such behavior. As a result, in piezoelectrics, MPB’s are highly sought after interfaces and form the basis of their applications in high-frequency electrostrictive actuators and sensors. Understanding and detecting external stimuli-caused structural phase transformations at MPB’s with the highest possible resolution is of paramount importance both from a fundamental and technological standpoint. However, the unambiguous detection of structural transformations and the associated elastic properties during transitions at the nanoscale especially in morphotropic piezoelectric thin films is a challenge, which yet remains to be addressed.
In this study, external field-induced reversible structural phase transformations and the associated elastic anomalies are dynamically probed and detected precisely in a nanoscopic volume via contact-resonance based spectroscopic piezoresponse techniques in the strain-engineered multiferroic morphotropic BiFeO3 (BFO) thin films [1,2]. The experimentally observed acoustic change unambiguously detects reversible morphotropic Tetragonal-Rhombohedral (T-R) structural phase transformation, and signifies modulation in elastic properties of the probed nanoscopic volume during such transitions. The experimentally observed nanoscale softening behaviour has been quantified using a model developed for the dynamics of the atomic force microscopy cantilever and a Hertzian model of contact mechanics [1].
Aided by activated kinetics of structural phase boundaries, a significant mechanical softening of about 6-10% occurs during nanoscale morphotropic phase transformations, and plays a critical role in the enhanced piezoelectricity of the strain-engineered BFO thin films. Moreover, the enhanced piezoelectricity during such morphotropic transitions arises primarily from intrinsic lattice contributions such as softening of the lattice and the activated morphotropic phase boundary kinetics as opposed to extrinsic contributions due to polarization switching and ferroelectric domain wall motion [1].
References
[1] P. Sharma, K. Kang, B.-K. Jang, C.-H. Yang, and J. Seidel, Advanced Electronic Materials (accepted-2016).
[2] P. Sharma, Y. Heo, B.-K. Jang, Y. Y. Liu, J. Y. Li, C.-H. Yang, and J. Seidel, Scientific Reports 6, 32347 (2016).
12:45 PM - ES10.1.05
Structure of Ferroelectric Vortices in a Single Layer PbTiO3 Thin Film
Shang-Lin Hsu 1 , Christopher Nelson 1 , Margaret McCarter 4 , Zijian Hong 2 , Anoop Rama Damodaran 1 , Julia Mundy 1 , Javier Junquera 3 , Long-Qing Chen 2 , Lane Martin 1 , Ramamoorthy Ramesh 1 4
1 Materials Science and Engineering, University of California, Berkeley, Berkeley, California, United States, 4 Physics, University of California, Berkeley, Berkeley, California, United States, 2 , The Pennsylvania State University, University Park, California, United States, 3 , Universidad de Cantabria, Avenida de los Castros s/n Spain
Show AbstractThe manipulation of charge and lattice boundary conditions of atomically precise low-dimensional complex oxide multilayers can stabilize ferroelectric polar vortices[1] with the potential for emergent chirality and resulting optical activity. The key outstanding question is the distribution, if any, of a polarization component along the axial direction of such vortices. The transverse components are well known from Transmission Electron Microscopy (TEM); however, similar characterization of the axial component is hampered by the non-uniform structure if projecting through a non-axial direction. This includes viewing multiple overlapping vortices and for directions normal to the substrate, low symmetry DyScO3 which includes its own large A-site and oxygen rotation antiferrodistortive structure. In this work we reduce the complexity of the ferroelectric / paraelectric superlattice to the study of a model system of a single confined PbTiO3 layer. Using TEM, we characterize the 3-D structure of the PbTiO3 layer and, combined with Resonant Soft X-ray Diffraction, Piezoresponse Force Microscopy and modeling by first principles and phase field, find confirmatory evidence of an axial component.
The study of a (SrTiO3)16 / (PbTiO3)16 / (SrTiO3)16 trilayer structure, grown by RHEED-assisted Pulsed Laser Deposition, using aberration corrected STEM and diffraction-contrast TEM is presented. Axial-view cross sections confirm that a single PbTiO3 film layer still exhibits ferroelectric vortices of ~10 nm periodicity. The 3-D macrostructure revealed by TEM along the film normal axis is a mixed-phase system consisting of vortices along both principle [100]pc and [010]pc directions, preferentially aligning to the [1-10]O orthorhombic direction of the DyScO3 substrate, as well as classic in-plane a1/a2 ferroelectric domains. Anti-phase type boundaries of the vortices are observed where clockwise and anti-clockwise rotations meet to form an axial domain wall, often punctuated with short segments of a-domains. This macrostructure matches closely with our phase-field simulations. Selected area diffraction and diffraction contrast TEM (dark field) of vortices along [1-10]o exhibit clear modulation of the axial planes across the vortices, consistent with the presence of a non-uniform axial polarization component. This meshes with PFM and RSXD results as well as first principles and phase field models. This study reveals both a rich macrostructure of vortices in a mixed phase system as well as the key microstructure of a topologically charged axial normal surface from the presence of an axial polarization.
[1] A. Yadav, C.T. Nelson, et al., Nature, 530, 198-201 (2016)
ES10.2: Multiferroics and Magnetoelectrics—Engineered Materials and Interfaces
Session Chairs
Venkatraman Gopalan
Pu Yu
Tuesday PM, April 18, 2017
PCC North, 200 Level, Room 222 A
2:30 PM - ES10.2.01
Recent Advances in Large Area Pulsed Laser Deposition—Epitaxial Growth of Complex Oxides on Silicon
Rik Groenen 1
1 Twente Solid State Technology, MESA+ Institute for Nanotechnology, University of Twente, Enschede Netherlands
Show AbstractPulsed Laser Deposition (PLD) has been established in recent years as a versatile thin film deposition technique for the near stoichiometric synthesis of materials including complex transition metal oxide thin films. These oxides offer a variety of exploitable properties, but despite this rich potential for use in electronics, actual industrial applications are relatively few as they rely on growth of films on substrate materials with sizes suitable for industrial applications, were silicon wafers define the standard of CMOS technology. This demands upscaling of the PLD process to grow high quality films on silicon wafers.
TSST has developed an PLD system with which oxide heterostructure growth on 4” silicon wafers is investigated and optimized, obtaining highly crystalline heterostructures with atomically sharp interfaces. Two important challenges in thin film growth on silicon wafers using PLD have been the focus of research in recent years. First, epitaxial growth of oxides on as-received silicon wafers is intrinsically prohibited by a native siliconoxide layer. Growth of YsZ buffer layers has proven to be an effective method to reduce and remove the native silicondioxide layer to form an epitaxial basis for oxide growth. Second, in PLD the dimension of the plasma plume is smaller than commonly used industrial wafer sizes, which is solved by scanning the plasma plume over the full wafer area. One final hurdle for full CMOS process compatibility remains: significantly lower process temperatures are required compared to small scale PLD growth experiments.
We present the results from this system on the growth of La0.67Sr0.33MnO3 (LSMO) thin films on high quality YsZ//CeO2//SrRuO3 buffer layers on 4'' silicon wafers. Film quality is investigated with X-Ray Diffraction and magnetic characterisation. Rocking curve measurements around the LSMO (002) Bragg reflection show values of ~1°, which is comparable to the quality of films grown in <1” substrate size small scale PLD experiments. A significant growth temperature dependence in the crystallinity and magnetic properties of LSMO is shown. With the introduction of the SRO layer LSMO films show single phase crystallinity and magnetic properties for temperatures as low as 250°C. When this SRO layer is lacking, fully amorphous film growth is observed at higher temperatures up to 550°C.
We speculate that the occurance of this LSMO high quality thin film growth at these lower growth temperatures could be understood by an improved surface diffusion induced by a changed crystal plane termination with the introduction of the SRO buffer layer. Recent work on BiFeO3 thin film growth shows qualitatively similar behaviour, where a dependence of growth kinetics and film characteristics on crystal plane termination is observed.
2:45 PM - *ES10.2.02
Phase Competition by Design in R0.5Ba0.5MnO3
Elizabeth Nowadnick 1 , Jiangang He 1 , Craig Fennie 1
1 , Cornell University, Ithaca, New York, United States
Show AbstractPhase competition between distinct ground states can arise when there are interactions on similar energy scales between the spin, charge, lattice, and orbital degrees of freedom. This competition can result in large responses to small external perturbations, for example the colossal magnetoresistance effect in the rare-earth manganites R1-xAxMnO3 arising out of competing ferromagnetic metallic and charge/orbital-ordered antiferromagnetic insulating states. Furthermore, phase competition between polar and magnetic ground states is a promising strategy to realize polarization (magnetization) control with a magnetic (electric) field, which is major goal in multiferroics research. In this regard, the half-doped A-site ordered manganite Sm0.5Ba0.5MnO3 is of particular interest, because the charge/orbital-ordered antiferromagnetic insulating state in this material is polar. We use a combination of group theoretic methods and first-principles calculations to elucidate the origin of this polar state, and show that epitaxial strain can tune the material to a regime where there is a strong competition between the polar insulating state and the ferromagnetic metallic state. We then utilize our understanding of the polarization and its coupling to charge/orbital order, spin, and structural distortions to explore how to achieve electric and magnetic field control of the magnetic and polar order parameters
3:15 PM - ES10.2.03
Ferromagnetic and Ferroelectric BiFeO3 Interlayers in Ferrite-Manganite Superlattices
Michael Fitzsimmons 1 2 , Er-Jia Guo 1 , Jonathan Petrie 1 , Manuel Roldan 3 , Qian Li 1 , Ryan Desautels 1 , Timothy Charlton 1 , Andreas Herklotz 1 , John Nichols 1 , John Freeland 4 , Sergei Kalinin 1 , Ho Nyung Lee 1
1 , Oak Ridge National Laboratory, Knoxville, Tennessee, United States, 2 Physics and Astronomy, University of Tennessee, Knoxville, Tennessee, United States, 3 , King Abdullah University of Science and Technology (KAUST), Thuwal Saudi Arabia, 4 , Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractComplex interactions across heterostructure interfaces of transition metal oxides enable functionality that is often not present in the constituent components. We report the synthesis of high-quality [001] oriented BiFeO3/La0.7Sr0.3MnO3 (BFO/LSMO) superlattices with BFO and LSMO layer thicknesses of 5 and 20 unit cells, respectively. Piezoresponse force microscopy identifies excellent ferroelectric response in ultrathin BFO. We find a novel ferromagnetic state is formed in BFO and can be extended throughout the BFO film when sandwiched between ferromagnetic manganites. The net magnetization in BFO is aligned opposite to the magnetization of the manganite layers. A net magnetization of 275 kA/m in the BFO layer at 10 K was obtained. The observed ferromagnetic order in the BFO and LSMO layers persists to 200 K and 310 K, respectively. We also present recent results from the same system with [111] oriented BFO/LSMO layers.
3:30 PM - *ES10.2.04
Atomically Engineered Ferroic Layers Yield a Room-Temperature Magnetoelectric Multiferroic
Julia Mundy 1 , Charles Brooks 2 , Megan Holtz 2 , Jarrett Moyer 3 , Hena Das 1 , Alejandro Rebola 2 , John Heron 4 , James Clarkson 1 , Zhiqi Liu 1 , Steve Disseler 5 , Alan Farhan 6 , Elke Arenholz 6 , Andreas Scholl 6 , Julie Borchers 5 , William Ratcliff 5 , Ramamoorthy Ramesh 1 , Craig Fennie 2 , Peter Schiffer 3 , David Muller 2 , Darrell Schlom 2
1 , University of California, Berkeley, Berkeley, California, United States, 2 , Cornell University, Ithaca, New York, United States, 3 , University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 4 , University of Michigan, Ann Arbor, Michigan, United States, 5 , NIST Center for Neutron Research, Gaithersburg, Maryland, United States, 6 , Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractMaterials that exhibit simultaneous order in their electric and magnetic ground states hold promise for use in next-generation memory devices in which electric fields control magnetism. Such materials are exceedingly rare, however, owing to competing requirements for displacive ferroelectricity and magnetism. Despite the recent identification of several new multiferroic materials and magnetoelectric coupling mechanisms, known single-phase multiferroics remain limited by antiferromagnetic or weak ferromagnetic alignments, by a lack of coupling between the order parameters, or by having properties that emerge only well below room temperature, precluding device applications. Here we present a methodology for constructing single-phase multiferroic materials in which ferroelectricity and strong magnetic ordering are coupled near room temperature. Starting with hexagonal LuFeO3—the geometric ferroelectric with the greatest known planar rumpling—we introduce individual monolayers of FeO during growth to construct formula-unit-thick syntactic layers of ferrimagnetic LuFe2O4 within the LuFeO3 matrix, that is, (LuFeO3)m/(LuFe2O4)1 superlattices. 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 substantially—from 240 kelvin for LuFe2O4 to 281 kelvin for (LuFeO3)9/(LuFe2O4)1. Moreover, the ferroelectric order couples to the ferrimagnetism, enabling direct electric-field control of magnetism at 200 kelvin. Our results demonstrate a design methodology for creating higher-temperature magnetoelectric multiferroics by exploiting a combination of geometric frustration, lattice distortions and epitaxial engineering.
ES10.3: Correlated Oxides—Interfaces and Magnetism I
Session Chairs
John Heron
Satoshi Okamoto
Tuesday PM, April 18, 2017
PCC North, 200 Level, Room 222 A
4:30 PM - ES10.3.01
Electrostatic vs Electrochemical Doping and Control of Ferromagnetism in Ion-Gel-Gated Ultrathin La0.5Sr0.5CoO3-δ
Jeffery Walter 1 , Guichuan Yu 2 , Biqiong Yu 2 , Helin Wang 1 , Martin Greven 2 , C. Daniel Frisbie 1 , Chris Leighton 1
1 Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota, United States, 2 School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota, United States
Show AbstractThe recently developed ionic liquid/gel gating techniques have proven remarkably expedient in the study of charge density effects in a variety of conductors, ranging from organics to complex oxides. The ability to controllably and reversibly induce surface charge densities > 1014 cm-2 has led to their extensive use in the study of superconductivity and insulator-metal transitions, but fewer works have explored their use in voltage-controlled magnetism. Here we present electrolyte gate control of the magnetism of ultrathin (8 unit cell) La0.5Sr0.5CoO3-δ (LSCO) films, using ion gels in electric double layer transistors. The LSCO films are initially metallic and ferromagnetic (TC ≈ 170 K), with anomalous Hall conductivity up to 40 S/cm, and strong perpendicular magnetic anisotropy. Transport measurements reveal that negative gate biases lead to reversible hole accumulation (i.e., predominantly electrostatic operation) up to some threshold, whereas positive bias immediately induces irreversibility. Experiments in inert/O2 atmospheres directly implicate oxygen vacancies in this irreversibility, supported by atomic force microscopy, X-ray photoelectron spectroscopy, and in situ X-ray diffraction performed at the Advanced Photon Source. The results are thus of general importance, suggesting that hole- and electron-doped oxides may respond very differently to electrolyte gating. Following this we demonstrate clear voltage-control of resistivity, magnetoresistance, and TC. The large anomalous Hall coefficient and perpendicular anisotropy combine to provide an exceptionally useful probe of magnetization, enabling measurement of the magnetic order parameter in the gated surface region. A 12 K shift in TC is obtained, comparing favorably to the state-of-the-art. Preliminary measurements on thinner films, with lower effective doping, suggest much stronger gate response, from a clustered magnetic insulating state (TC ≈ 0 K) to a long-range ferromagnetic metallic one (TC ≈ 150 K), i.e., a voltage-induced magnetic percolation transition.
4:45 PM - *ES10.3.02
Spin Orbit Torques and Proximity-Induced Magnetism in Thulium Iron Garnet Heterostructures
C. A. Ross 1
1 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractIron garnets with composition R3Fe5O12 are ferrimagnetic insulators (FMIs) whose magnetic properties can be modified by R-site substitution. Y3Fe5O12 (YIG) is the most widely studied magnetic garnet, but YIG films typically exhibit in-plane magnetization dominated by shape anisotropy. Here we describe the growth and spintronic properties of Tm3Fe5O12 (TmIG) films grown epitaxially on Gd3Ga5O12 (GGG) (111) substrates by pulsed laser deposition. TmIG (111) films exhibit perpendicular magnetic anisotropy (PMA) as a result of magnetocrystalline anisotropy plus a magnetoelastic contribution due to the in-plane tensile strain. MOKE, vibrating sample magnetometry and magnetic force microscopy confirm the presence of PMA, a near-bulk magnetization even for films as thin as 5.6 nm (5 unit cells), and coercivity as low as 18 Oe, and XMCD shows the ferrimagnetic configuration of the tetrahedral Fe and the Tm and octahedral Fe trivalent ions. Both anomalous Hall effect and charge-current-induced switching of the magnetization via spin orbit torque were demonstrated in heterostructures consisting of heavy metal/TmIG. Spin Hall magnetoresistance measurements indicate a high spin mixing conductance at the Pt/TmIG interface, and full bidirectional reversal of the magnetization of an 8 nm thick TmIG film was demonstrated at 1 – 2 x 1011 A/m2 current density in Pt in the presence of a modest fixed in-plane field. TmIG/(Bi,Sb)2Te3 topological insulator (TI) heterostructures were also fabricated in which proximity-induced magnetism was detected in the TI using polarized neutron reflectometry. These results demonstrate the potential of a PMA FMI in revealing spintronic phenomena relevant to low-dissipation electronics.
5:15 PM - ES10.3.03
Magneto-Optical Isolator Designs Inspired by Seedlayer-Free Terbium Iron Garnets with Opposite Chiralities
Prabesh Dulal 1 , Cui Zhang 2 , Thomas Gage 1 , Andrew Block 1 , Emiliana Cofell 3 , David Hutchings 2 , Bethanie Stadler 1
1 , University of Minnesota, Minneapolis, Minnesota, United States, 2 , University of Glasgow, Glasgow United Kingdom, 3 , Scripps College, Claremont, California, United States
Show AbstractCe- and Bi-doped yttrium iron garnets (Y3Fe5O12 / YIG) exhibit enhanced magneto-optical properties such as Faraday rotation (FR) and nonreciprocal phase shift (NRPS). These garnets have dominated the research in magneto-optical films for nonreciprocal photonics, imaging, recording, and spatial light modulators. However, monolithic integration of these thin films requires a two-step deposition method in which an ultrathin YIG seedlayer must be grown prior to the deposition of the doped garnet layer. Simulations of light travelling through garnet-cladded SOI (silicon-on-insulator) waveguides show that even a 20nm thin YIG seedlayer decreases the interaction of light with the doped YIG layer by 40%. Here, we present a novel material, terbium Iron garnet (Tb3Fe5O12 / TIG) that can be grown on semiconductor substrates without seedlayers and hence is much more efficient than the doped rare earth garnets that require seedlayers.
TIG, bismuth doped TIG (Bi:TIG) and cerium doped TIG (Ce:TIG) were grown on double-side polished Si, MgO and quartz substrates using metallic targets via reactive sputtering. X-ray diffraction (XRD) indicated that single phase, polycrystalline garnet was obtained after a rapid thermal anneal at 900°C for 2 min in oxygen. The magnetizations were measured using vibrating sample magnetometry (VSM). FR (TIG=500 ο/cm, Bi:TIG= -500 ο/cm and Ce:TIG= -2600 ο/cm) was measured at 1545.2 nm. Using similar sputtering and annealing parameters, single phase Ce:YIG thin films were grown on the YIG, TIG and Bi:TIG seedlayers. Mode solver simulations of SOI waveguides with garnet claddings show that the FR produced by Ce:TIG on SOI waveguides is 3 times better than that produced by Ce:YIG/YIG claddings. Simulations also show that the matching FR chirality of Bi:TIG and Ce:YIG (both negative) makes Bi:TIG a much better seedlayer for Ce:YIG than YIG (positive). Results show that the FR of an SOI waveguide with Ce:YIG grown on Bi:TIG seedlayer is almost 1.5 times greater than that produced by Ce:YIG grown on YIG seedlayer.
Finite Difference Time Domain (FDTD) simulations show that the opposite chiralities of TIG (+) & Bi:TIG/Ce:YIG (-) can be exploited to develop novel polarization diverse, push-pull, quasi-phase matched (QPM) waveguide optical isolators with significant reduction in device footprint, where the smallest waveguide device (0.8μmx1.6μmx 350μm) is obtained by alternating 3.85μm long segments of TIG and Ce:YIG films on a fused quartz substrate.
5:30 PM - *ES10.3.04
Controllable In-Plane Uniaxial Magnetic Anisotropy in Ni/NiO(110) Heterostructures
Yu-Jun Zhang 1 , Liang Wu 1 , Qinghua Zhang 1 , Atsushi Fujimori 2 , Jing Ma 1 , Yuan-Hua Lin 1 , Ce-Wen Nan 1
1 , Tsinghua University, Beijing China, 2 Department of Physics, University of Tokyo, Tokyo Japan
Show AbstractIn numerous heterostructures, novel physical phenomena could emerge at interfaces, for example, LaAlO3/SrTiO3 interfaces interface is electrically conductive under the specific conditions. In this talk, we will present a peculiar uniaxial magnetic anisotropy investigated in Ni(polycrystalline)/NiO(epitaxial)/(110)SrTiO3 heterostructure. It is demonstrated that antiferromagnetic ordering of NiO induced interface exchange coupling should not be responsible for the anisotropy according to the temperature dependence. And the soft X-ray linear dichroism results show a preferential occupation of orbital parallel to in-plane [100] at Ni/NiO interface. So it is speculated that the origin of this uniaxial anisotropy is closely related to the occupation of Ni 3d orbitals at the interface, and magnetocrystalline anisotropy in the Ni nor NiO layer plays an insignificant role. The magnetocrystalline anisotropy and piezoelectric strain may be utilized to manipulate this uniaxial anisotropy and realize controllable in-plane easy axis switching.
ES10.4: Poster Session I
Session Chairs
Wednesday AM, April 19, 2017
Sheraton, Third Level, Phoenix Ballroom
9:00 PM - ES10.4.01
Room Temperature Magnetocapacitance Effects in Multiferroic M-type Hexaferrites—Bulk and Thin Film
Rujun Tang 1 , Hao Zhou 1 , Hao Yang 2
1 School of Physics, Optoelectronics and Energy, Soochow University, Suzhou, Jiangsu, China, 2 School of Science, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu, China
Show AbstractThe multiferroic hexaferrites have aroused much intention in the recent years. Certain amount of Sc substitution in the M-type hexaferrite BaFe12-xScxO19 (BFSO) can lead to a conical magnetic structure and exhibit magnetoelectric (ME) effects [1]. However, the reported studies on the BFSO are focused on its ME coupling at low temperatures. The room temperature ME properties have not been well understood. In this work, the magnetocapacitance (MC) effects in M-type hexaferrite BaFe10.2Sc1.8O19 have been investigated in both bulk and thin film types of samples around the room temperature (240 K- 360 K). Results show that large MC effects are observed near room temperature in both polycrystalline bulk and epitaxial thin film samples. Frequency dependence analysis shows that in the low frequency region, the Maxwell-Wagner type magnetoresistance effect is the dominant mechanism for the MC effects in the polycrystalline bulk sample. In the epitaxial thin film sample, the electrode-sample interfaces contribute to the MC effects, but their contributions are very small. In the high frequency region, for both bulk and thin film samples, the inverse-Dzyaloshinskii-Moriya interaction induced ME-type spin-phonon coupling effect is the dominant factor for the MC effects. This work can help better application of BFSO in the novel ME devices.
[1] Y. Tokunaga et’al. Phys. Rev. Lett. 105, 257201 (2010).
9:00 PM - ES10.4.02
Oxygen Transport-Driven Suppression of Phase Separation in the Double Perovskite Oxide La2MnNiO6
Steven Spurgeon 1 , Peter Sushko 1 , Arun Devaraj 1 , Yingge Du 1 , Timothy Droubay 1 , Scott Chambers 1
1 Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington, United States
Show AbstractVertically-aligned nanocomposite (VAN) thin films exhibit a diverse range of emergent properties, including exchange bias and magnetoelectricity. While molecular beam epitaxy (MBE) has enabled the synthesis of highly pure, single-crystalline thin films, deterministic engineering of VANs remains challenging due to a poor understanding of complex nucleation and growth process. Here we combine atomic-scale probes and ab initio theory calculations to explore the driving forces behind secondary phase formation in the model double perovskite, La2MnNiO6 (LMNO). We focus on the early stages of the LMNO growth process, observing an initial 3 to 5 nm defect-free LMNO region upon which columnar NiO phase separation occurs. Ab initio simulations of prototype point defects versus LMNO thickness suggest that MBE-grown films contain oxygen vacancies that can promote the formation of Mn-Ni anti-site defects. When the LMNO layer is thin, oxygen transport can limit the concentration of these defects; however, beyond 3 to 5 nm thickness isolated vacancies and anti-sites can coalesce into large-scale lattice defects, forming extensive non-ferromagnetic regions. Our results highlight the important role played by the transport of oxygen from the substrate and suggest new routes to control the nucleation and growth of secondary phases in nanocomposite thin films.
9:00 PM - ES10.4.03
Controlled Deposition and Multiferroic Behavior of Ba0.70Sr0.30TiO3 - CoFe2O4 and PbZr0.52Ti0.48O3-CoFe2O4 Vertical Aligned Nanostructures
Sergey Basov 1 2 , Catherine Elissalde 2 , Luc Piraux 1
1 Institute of Condensed Matter and Nanosciences, Université catholique de Louvain, Louvain-la-Neuve Belgium, 2 ICMCB-CNRS, Université de Bordeaux, Pessac France
Show AbstractMultiferroic materials are among the most attractive multifunctional materials due to the possibility of combining and coupling ferroelectric, ferromagnetic and ferroelastic orders leading to many multifunctional applications: ferromagnetic memories, ferroelectric sensors, ferroelastic detectors, actuators and other microwave devices. Multiferroic nanocomposites, combining piezoelectric and magnetostrictive phases, present the advantage to control magnetoelectric (ME) coupling between polarization and magnetization through the interfacial strain and elastic interaction. The coupling is observed by means of ferroelectric phase transition induced by magnetic field in perovskite structures (BaTiO3, BaxSr1-xTiO3, PbZrxTi1-xO3) or vice versa ferromagnetism induced by electric field in spinel structure (CoFe2O4).
In our research, two strategies are followed for the material design: i) (1-3) structure where vertically aligned ferrimagnetic nanopillar arrays (1) are embedded in a ferroelectric matrix (3), and ii) (1-3) structure where three-dimensional self-supported interconnected ferrimagnetic nanowire networks (1) are embedded in a ferroelectric matrix (3). The objective is to increase the strain and ME coupling of multiferroic nanocomposites by increasing interfacial surface area between the two phases, by reducing clamping between multiferroic material and a rigid substrate or by strengthening the coupling between two phases.
The first approach combines electrochemical and sol-gel processes. Its efficiency and flexibility has been demonstrated in the case of Ni@BaTiO3 nanocable arrays1. The electrodeposition of CoFe2 vertically aligned nanopillar arrays and 3D interconnected nanowire networks within porous templates is followed by template dissolution, sol-gel impregnation of PbZr0.52Ti0.48O3 and thermal treatment to crystallize the dielectric phase and to directly oxidize the magnetic phase while preserving the global architecture. The second approach we develop is the deposition by rf magnetron sputtering of Ba0.70Sr0.30TiO3 onto supported CoFe2 and CoFe2O4 nanopillar arrays. The microstructural and morphological evaluations of nanocomposites include XRD and SEM characterizations. For magnetic hysteresis and capacitance-frequency over wide range of temperatures, an alternating gradient magnetometer and impedance analyser were utilized, respectively. The ME voltage is determined as a function of DC magnetic field, and temperature in longitudinal geometry using adjusted Quantum Design Physical Property Measurement System.
Two types of two-phases multiferroic nanocomposites have been prepared. The magnetoelectric coupling in the nanopillar arrays embedded inside the matrix have been observed and can be interpreted by the good ferroelectricity and ferrimagnetism of the two phases, along with the reduced clamping effect and the large interface area, which can enhance the strain interaction.
[1] Sallagoity D. et. al. 2015 J. Mater. Chem. C 3, 107-11
9:00 PM - ES10.4.04
Orbital Preferential Occupation Induced Controllable Uniaxial Magnetic Anisotropy Observed in Ni/NiO(110) Heterostructures
Yu-Jun Zhang 1 , Liang Wu 1 , Ji Ma 1 , Qing-Hua Zhang 1 , Atsushi Fujimori 2 , Jing Ma 1 , Yuan-Hua Lin 1 , Ce-Wen Nan 1
1 , Tsinghua University, Beijing China, 2 , University of Tokyo, Tokyo Japan
Show AbstractUnexpected physical phenomena could emerge at heterostructure interfaces. Interface effects are also capable to give rise to magnetic anisotropy. In this work, a peculiar uniaxial magnetic anisotropy in polycrystalline Ni/epitaxial NiO/SrTiO3 (110) heterostructure is investigated. Thickness dependence of the anisotropy confirms its interface effect nature. Antiferromagnetic ordering of NiO induced interface exchange coupling should not be responsible for the anisotropy according to the temperature dependence. Our soft X-ray linear dichroism results show a preferential occupation of orbital parallel to in-plane [100] at Ni/NiO interface. The origin of this uniaxial anisotropy is closely related to the occupation of Ni 3d orbitals at the interface. The magnetocrystalline anisotropy and piezoelectric strain may be utilized to manipulate this uniaxial anisotropy and realize controllable in-plane easy axis switching, which could be potential for future application on spintronics devices.
9:00 PM - ES10.4.05
Magnetic Anisotropy of CoFe2O4 Nanotubes Synthesized by Radical-Enhanced ALD
Pui Lam Cheung 1 , Jeffrey Chang 1 , Jane Chang 1
1 Chemical and Biomolecular Engineering, University of California, Los Angeles, Los Angeles, California, United States
Show AbstractMultiferroic materials, exhibiting ferroelectricity and ferromagnetism simultaneously, have attracted interests for energy efficient multifunctional applications at nanoscale such as memories, antennas and actuators. While room temperature single-phase multiferroic materials such as bismuth ferrite provide insufficient magnetoelectric effect, composite systems have enhanced magnetoelectric properties by combining piezoelectric materials and magnetostrictive materials through strain. However, such strain-mediated approach in thin film composites is limited by interfacial area and substrate clamping. Ferromagnetic nanowires, on the other hand, provides a new degree of freedom in manipulating magnetic properties through shape anisotropy.
In this work, cobalt ferrite (CoFe2O4) nanotubes were grown on anodic aluminum oxide membranes using radical enhanced atomic layer deposition (RE-ALD) to study magnetic shape anisotropy. The deposition was achieved using cobalt and iron (tmhd)-based metalorganic precursors (tmhd = 2,2,6,6,tetramethyl-3,5-heptanedionato) and oxygen radicals at 200oC with a growth rate of 0.18nm/cycle. Nanotubes array were formed inside the nanoporous membranes with pore size of 18nm, 35nm and 80nm. The morphology and magnetic properties of the nanotubes were studied using scanning electron microscopy, SQUID and energy dispersive X-ray spectroscopy. It was observed that as the wall thickness of the nanotube increases, the magnetic easy axis was switched from perpendicular to parallel to the nanowires axis, with an increased saturation magnetization. As cobalt ferrite nanowires were formed, the preferential easy axis was reversed, which could potentially be implemented in manipulating of magnetization orientation if coupled to a piezoelectric material for device applications.
9:00 PM - ES10.4.06
High-Performance CuFe2O4 Epitaxial Thin Films with Enhanced Ferromagnetic Resonance Properties
Hong Wang 1
1 , Xi'an Jiaotong University, Xi'an China
Show AbstractHighly epitaxial thin films of copper ferrite (CuFe2O4) have been fabricated on MgAl2O4 (001) substrates at growth temperature of 400 oC for the first time through a RF sputtering method. Structural analyses through HRXRD, Raman spectroscopy, and HRTEM all confirm tetragonal spinel phase of CuFe2O4 epitaxial film and high tetragonal distortion (c/a=1.08) of its unit cells. The 50-nm-thick T-CuFe2O4 epitaxial film shows unique soft magnetism with small coercivity of 23 Oe and decreased magnetization. However, superior ferromagnetic linewith of only ~93 Oe in the post-annealed T-CuFe2O4 film over linewidth of ~1500 Oe in T-CuFe2O4 single crystal bulk material is also observed, which indicates that epitaxial growth of oxide thin films combining with proper heat-treatment induced cation engineering can impose novel functionalities.
9:00 PM - ES10.4.07
Impact of Internal Electric Field on the Strain Memory Effect of Poled BiScO3-PbTiO3 Ceramics
Jianguo Chen 1 , Jinrong Cheng 1
1 , Shanghai University, Shanghai China
Show AbstractFerroelectric and strain hysteresis loops of the poled and aged Mn modified 036BiScO3-0.64PbTiO3 (BS-PT-Mn) ceramics were measured under different electric fields and frequencies at room temperature. The ferroelectric loops of BS-PT-Mn ceramics were asymmetric, indicating the existence of the inner bias electric field. The coercive and inner bias electric field of BS-PT-Mn ceramics for Mn = 2 mol% were about 30 and 5.5 kV/cm, respectively, which were much larger than those of traditional “hard” PZT ceramics. Strain memory effect was observed in the BS-PT-Mn ceramics, and very sensitive to the internal electric field. The strain memory increased with the Mn content, and reached the maximum at the Mn content of 1 mol%, which was 0.36%, then decrease with further increase. It was interesting that the strain memory of BS-PT-Mn ceramics for Mn = 2 and 3 mol% was stable with the magnitudes and frequencies of electric field, which may be owing to the large inner electric and coercive field.
9:00 PM - ES10.4.08
Investigation of Ferroelectric and Ferromagnetic MPBs of Modified BiFeO3-PbTiO3 Solid Solutions
J.R. Cheng 1 , Jianguo Chen 1 , Dengren Jin 1
1 , Shanghai University, Shanghai China
Show AbstractIt is very difficult to obtain the single phase multiferroics by introducing the magnetic ions in ferroelectrics due that conventional ferroelectricity requires closed-shell d0 or s2 cations, whereas ferromagnetic order requires open-shell dn configurations with unpaired electrons. Perovskite BiFeO3 has both electric and magnetic orderings well above room temperature, however, its cycloidal magnetic structure precludes bulk magnetization and linear magnetoelectric coupling. Most recently, BiFeO3 based solid solutions exhibit enhanced insulation, piezoelectric and even ferromagnetic properties in the morphotropic phase boundaries (MPBs), which attract much attention to explore the single phase multiferroics with magnetoelectric properties.
In this talk, different cations of La3+, Ga3+ and Ba3+have been introduced into the A- and/or B- sitesof (1-x)BiFeO3-xPbTiO3 (BFO-PT) solid solutions to improve their piezoelectric and ferromagnetic properties. It has been found that anti-ferromagnetic BFO and non-magnetic PT form solid solutions producing weak ferromagnetic responses in the vicinity of the MPBs. The A-site La and Ba modification promote the formation of the rhombohedral phase resulting in the relaxor behavior of BFO-PT ceramics. Moreover, with increasing the content of La, Ba and Ga, the ferromagnetic properties of BFO-PT ceramics were enhanced obviously, accompanied by appearance of the dielectric relaxation. The magnetic and dielectric transition temperature are much close and well above room temperature implying that the magnetic field and magnetic transition might have strong effect on dielectric properties. The ferroelectric transition, on the other hand, should affect the magnetic properties definitely in this modified BFO-PT system. It is concluded that modified BFO-PT ceramics are unique multiferroic materials which are expected to produce the magnetoelectric coupling for applicationsof the next generation sensors and actuators.
9:00 PM - ES10.4.09
Improvement of Dielectric Tunability for Ba0.6Sr0.4TiO3 Thin Films with BaxSr1-xTiO3 Buffer Layer on Stainless Steel Substrates
Hanting Dong 1 , Hongfang Li 1 , Guoping Lu 1 , Dengren Jin 1 , Jianguo Chen 1 , Jinrong Cheng 1
1 , Shanghai University, Shanghai China
Show AbstractSimultaneously acting as bottom electrode and substrates, stainless steel (SS) slices, exhibit their advantages in low cost, integrating films with MEMS-structure devices. By depositing on SS substrates, Barium strontium titanate (BST) thin films have been expected to their potential applications in MEMS-structure tunable microwave devices. In this paper, sol-gel drived Ba0.6Sr0.4TiO3 thin films with ultrathin BaxSr1-xTiO3 (x=0.2, 0.35, 0.5, 0.65, 0.8 and 0.95) buffer layer were fabricated on LaNiO3 buffered SS substrates. Effects of BaxSr1-xTiO3 layer on phase structures and dielectric properties of such BST films were investigated. Results show that the phase structure of all samples is the typical perovskite structure, and the shifted (110) peaks indicate that their strains can be adjusted by changing the x value of BaxSr1-xTiO3 layer. Furthermore, BST thin films with smaller strains can achieve larger tunability, and the maximum of tunability can reach 32.5% under the electric field of 300 kV/cm. Meanwhile, their dielectric properties are also theoretically analyzed via a modified thermodynamic model to consider lattice misfit stress and thermal induced stress, and the results of calculated and experimental results are recorded in Fig.1. The experimental dielectric constants and tunabilities are in good agreement with the calculated results, indicating that dielectric properties of BST thin films can be adjusted by introducing BaxSr1-xTiO3 buffer layer to regulate the lattice misfit stress.
Symposium Organizers
John Heron, University of Michigan
Satoshi Okamoto, Oak Ridge National Laboratory
Morgan Trassin, ETH Zürich
Pu Yu, Tsinghua University
Symposium Support
CrysTec Gmbh
Lake Shore Cryotronics Inc
NT-MDT America Inc.
Radiant Technologies, Inc
Twente Solid State Technology B.V.
ES10.5: Frontiers in Spintronics I
Session Chairs
Pietro Gambardella
Fengyuan Yang
Wednesday AM, April 19, 2017
PCC North, 200 Level, Room 222 A
9:30 AM - *ES10.5.01
Antiferromagnetic Spintronics
Tomas Jungwirth 1 2
1 , Institute of Physics, Czech Academy of Sciences, Prague Czech Republic, 2 School of Physics and Astronomy, University of Nottingham, Nottingham United Kingdom
Show AbstractLouis Néel pointed out in his Nobel lecture that while abundant and interesting from theoretical viewpoint, antiferromagnets did not seem to have any applications. Indeed, the alternating directions of magnetic moments on individual atoms and the resulting zero net magnetization make antiferromagnets hard to control by tools common in ferromagnets. Strong coupling would be achieved if the externally generated field had a sign alternating on the scale of a lattice constant at which moments alternate in antiferromagnets. However, generating such a field has been regarded unfeasible, hindering the research and applications of these abundant magnetic materials. We will discuss a recent prediction that relativistic quantum mechanics may offer a staggered current induced field whose sign alternates within the magnetic unit cell. The staggered spin-orbit field can facilitate a reversible switching of an antiferromagnet with comparable efficiency to the switching of ferromagnets by conventional uniform magnetic fields. We will then discuss suitable antiferromagnetic materials and a demonstration of the complete writing/storage/readout functionality in PC compatible demonstrator device. The absence of dipolar fields in the zero net moment antiferromagnets allows for a multiple-stability of the memory states that are invisible to magnetic probes and robust against external magnetic field perturbations. Moreover, antiferromagnets have ultra-fast internal spin dynamics, opening the prospect of picosecond timescales for switching, both in the coherent single domain regime and by ultra-fast domain wall motion.
References
[1] P. Wadley et al. Science 351, 587 (2016); C. Marrows (Editorial), Science 351, 558 (2016).
[2] T. Jungwirth et al., Nature Nanotech. 11, 231 (2016); Editorial, Nature Nanotech. 11, 231 (2016).
10:00 AM - ES10.5.02
Correlation of the Conductivity/Magnetic Properties and the Electronic, Crystalline and Compositional Structure of Strongly Correlated Complex-Oxide Thin Films for Spintronic Applications
Juan Rubio Zuazo 1 2 , Iciar Arnay 1 2 , Aida Serrano Rubio 1 2 , Eduardo Salas Colera 1 2 , German Castro 1 2
1 , SpLine CRG BM25 at the ESRF The European Synchrotron, Grenoble France, 2 Instituto de Ciencia de Materiales de Madrid ICMM, Consejo Superior de Investigaciones Científicas CSIC, Madrid Spain
Show AbstractWe study the structural and electronic properties of strongly correlated complex-oxide thin films and interfaces using Hard X-ray Photoelectron Spectroscopy (HAXPES), and Grazing Incidence X-ray diffraction (GIXRD) at the BM25-SpLine beamline (Branch B) at the ESRF. Strongly correlated complex-oxide exhibit a wide variety of interesting physical properties which originate from mutual coupling among spin, charge and lattice degrees of freedom. Usually, the interface drives the magnetic and electric response of the heterostructure. The chemical, mechanical, electric and magnetic properties of such devices are often intimately related to the structure, composition profile and morphology. Several mechanisms are present as crystallographic space group modification, presence of oxygen vacancies, dislocations due to lattice strain, deviation from stoichiometry, phase segregation. In general all these phenomena modify the intrinsic properties of the materials used at the heterostructure, offering a unique way to produce artificial correlated materials with tailored properties. The growth of these materials in thin film form opens possibilities for magneto-electronic and spintronic devices applications. The results shown here are focused on the study of the influence of buried interfaces on the electric and magnetic properties of CMR and multiferroics systems. We will show the experimental methodologies at SpLine based on synchrotron radiation techniques to gain quantitative knowledge on the crystallographic and electronic properties at the interface between different complex oxides. There are few techniques able to provide an accurate insight of what is happening at these buried interfaces which in general are buried by several tens of nanometres in the material. The simultaneous combination of hard and soft X-ray photoelectron spectroscopy with surface/interface X-ray diffraction gives unique capabilities in this respect. Here we will present a series of example to show how the interface properties can change the magnetic-conductivity properties.
10:15 AM - *ES10.5.03
Spin Dynamics in Antiferromagnets
Di Xiao 1 , Satoshi Okamoto 2
1 , Carnegie Mellon University, Pittsburgh, Pennsylvania, United States, 2 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractThe field of spintronics studies intriguing phenomena attributed to the interplay between magnetization and electrons. Recently, antiferromagnets (AFMs) are shown to be promising candidates for next-generation spintronic materials, as they hold potential to replace ferromagnets based on three salient features: 1) AFMs typically operate at Terahertz frequency. 2) AFMs bear a unique degree of freedom that refers to the chirality of spin wave. 3) AFMs have vanishing magnetization which helps in stabilizing and scaling down a magnetic device. In this talk, I will introduce recent progress in understanding these crucial properties of AFMs as well as their possible applications. I will first discuss how spin pumping and current-induced torques manifest in AFMs and the relations to their ferromagnetic counterparts. Then I will turn to the spin wave dynamics without the participation of electrons, and show that the degeneracy of spin wave modes enables a novel scheme in processing information. These phenomena can be exploited to create multifunctional Terahertz magnetic devices with low dissipation.
ES10.6: Correlated Oxides—Interfaces and Magnetism II
Session Chairs
Wednesday PM, April 19, 2017
PCC North, 200 Level, Room 222 A
11:30 AM - *ES10.6.01
FMR-Driven Pure Spin Transport from Y3Fe5O12 Thin Films to Metals and Antiferromagnetic Insulators
Fengyuan Yang 1
1 , The Ohio State University, Columbus, Ohio, United States
Show AbstractSpintronic applications rely on the generation, manipulation, and detection of spin currents mediated by spin-polarized itinerant charges or magnetic excitations. In recent years, pure spin transport driven by ferromagnetic resonance (FMR) spin pumping or a thermal gradient has attracted intense interest and become one of the most active frontiers in condensed matter and materials physics. Extensive research efforts have demonstrated pure spin currents in a broad range of materials, which enrich our understanding of dynamically-driven spin transport and open new paradigms for energy-efficient, spin-based technologies.
Building on the high-quality Y3Fe5O12 (YIG) films grown by off-axis sputtering and the large inverse spin Hall effect (ISHE) signals enabled by these films, we have characterized pure spin currents in nonmagnetic (NM) metals, ferromagnetic (FM) metals, nonmagnetic insulators, and antiferromagnetic (AF) insulators [1-4]. The spin Hall angles determined for a series of transition metals show that atomic number, d-electron count, and film thickness play important roles in spin Hall physics. More interestingly, we observed robust spin currents from YIG to Pt across AF insulators, which initially enhances the ISHE signals and can transmit spin currents up to 100 nm thickness, demonstrating highly efficient spin transport through an AF insulator carried by magnetic excitations. Our results show a strong correlation between spin propagation lengths in the AF insulators with the AF ordering temperatures. An excellent linear relationship between the spin decay length in the AF insulators and the damping enhancement in YIG was observed, which suggests the critical role of magnetic correlations in the AF insulators as well as at the AF/YIG interfaces for spin transport in magnetic insulators. Recent results about temperature dependence of FMR spin pumping across AF insulators will also be discussed.
References:
1. A. Prakash, et al. PRB 94, 014427 (2016).
2. J. T. Brangham, et al. PRB 94, 054418 (2016).
3. H. L. Wang, et al. PRB 91, 220410(R) (2015).
4. H. L. Wang, et al. PRL 113, 097202 (2014).
12:00 PM - ES10.6.02
Anomalous Hall Effect by Charge Transfer at Non-Polar Interfaces in SrIrO3/SrMnO3 Superlattices
John Nichols 1 , Changhee Sohn 1 , Soyeun Kim 2 , Satoshi Okamoto 1 , Daniel Haskel 3 , John Freeland 3 , Tae Won Noh 2 , Michael Fitzsimmons 1 , Ho Nyung Lee 1
1 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 , Seoul National University, Seoul Korea (the Republic of), 3 , Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractWe have observed ferromagnetism in SrIrO3/SrMnO3 superlattices grown on SrTiO3 (001) substrates by pulsed laser epitaxy. Polarized neutron reflectometry and x-ray dichroism unveil ferromagnetically ordered spins at the interfaces, and its magnetization could be readily tuned by varying the superlattice layer thicknesses. From x-ray absorption measurements, the interfacial magnetization is found to originate from interfacial charge transfer, which is also confirmed by density functional theory calculations. It is worth stressing that we have found that the interfacial charge transfer could occur in SrIrO3/SrMnO3 superlattices, despite the nearly identical work function and non-polar interfaces between SrIrO3 and SrMnO3. Such large transfer is attributed to the formation of strong 3z2-r2 bonding orbitals between neighboring Mn and Ir, based on the molecular orbital picture. Moreover, we have also observed the anomalous Hall effect in our superlattices, which is produced by the interfacial magnetism, indicating that the strong interfacial coupling in 3d-5d oxide superlattices can lead to a new means to develop spintronic devices.
*This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.
12:15 PM - *ES10.6.03
Emergent Phenomena at the LaTiO3/SrTiO3 Interface—Evidence for Giant Rashba Spin Splitting
Michael Veit 1 , Brad Ramshaw 2 , Mun Chan 2 , Yuri Suzuki 1
1 , Stanford University, Stanford, California, United States, 2 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractComplex oxide interfaces have been explored extensively in recent years as novel functionality or phenomenon has been generated at these interfaces due to mismatches in bands, valences, and interaction lengths. The most well known example of such emergent phenomena at complex oxide interfaces has been the discovery of metallicity at the interface of two band insulators LaAlO3 (LAO) and SrTiO3 (STO). We have recently discovered that low dimensional metallic behavior at the interface of a Mott insulator LaTiO3 (LTO) and a band insulator STO is characterized by two sets of Shubnikov-de Haas (SdH) oscillations, substantial anisotropic magnetoresistance (AMR) and a weak anti-localization correction to the magnetoconductivity in LTO/STO heterostructures – all of which are consistent with strong Rashba spin-orbit coupling. One set of SdH oscillations are observed at relatively low fields before reaching the quantum limit, and a Berry's phase of π is observed in these oscillations. Another set of oscillations are observed at higher field. These two sets of oscillations enable us to deduce a Rashba coupling coefficient of 2.0 x 10-11 eVm which is an order of magnitude larger than that observed in LAO/STO. The magnetoconductivity exhibits a field dependence that can be attributed to weak anti-localization. Additionally, the in-plane magnetoresistance exhibits an angular dependence consistent with a Rashba system. The observed AMR is much larger than other oxide systems such as LAO/STO. Such a large Rashba coupling suggests that such a Mott/band insulator interface may be an excellent candidate for spintronics.
12:45 PM - ES10.6.04
Electronic Properties of Electron-Doped CaMnO3 Thin Films Probed by Magnetotransport and Angle-Resolved Photoemission Spectroscopy
Lorenzo Vistoli 1 , Anke Sander 1 , Marius-Adrian Husanu 2 3 , Federico Bisti 2 , Vladimir Strocov 2 , Vincent Garcia 1 , Manuel Bibes 1
1 , Unité Mixte de Physique CNRS/Thales, Université Paris-Sud, Université Paris-Saclay, Palaiseau France, 2 , Paul Scherrer Institut, Swiss Light Source, Villigen Switzerland, 3 , National Institute of Materials Physics, Magurele Romania
Show AbstractCaMnO3 is an antiferromagnetic charge-transfer insulator pertaining to the widely studied family of colossal magnetoresistance manganites. The peculiarity of this oxide is that the chemical substitution of Ca2+ by Ce4+ gives two electrons to the system and raises the Fermi level, inducing a transition to a metallic and weakly ferromagnetic phase at 5% Ce concentration in bulk [1] and only 2% in compressively strained thin films grown on YAlO3(001) [2]. The low critical electron doping required to reach a metallic state makes this compound very interesting as a channel material for field effect studies [3] [4], where a metal-to-insulator transition would be modulated by electrostatic gating. In parallel, the low critical dopant concentration is not accompanied by structural changes, thus making Ce-doped CaMnO3 an attractive system for investigating carrier delocalization and conductive band formation in correlated oxides, i.e. to explore the interplay between electron doping, correlation effects and disorder in perovskite oxides.
The manganite thin films were grown by pulsed laser deposition on YAlO3(001) substrates. The combination of scanning probe microscopy, X-ray diffraction techniques and advanced transmission electron microscopy and electron energy loss spectroscopy reveals that the epitaxial thin films are fully coherent with the substrate and that Ce-doping induces a corresponding change of the Mn oxidation state [5].
In this presentation we will report the doping and thickness dependence of the transport and structural properties of thin Ca1-xCexMnO3 films. In addition, we will use soft X-ray angle-resolved photoelectron spectroscopy to directly inspect the electronic structure in momentum space, to establish the influence of doping on the band structure and Fermi surface while looking for possible polaronic signatures.
[1] E. N. Caspi, M. Avdeev, S. Short, J. D. Jorgensen, M. V. Lobanov, Z. Zeng, M. Greenblatt, P. Thiyagarajan, C. E. Botez, and P. W. Stephens, Phys. Rev. B 69, 104402 (2004).
[2] P.-H. Xiang, H. Yamada, H. Akoh, and A. Sawa, J. Appl. Phys. 112, 113703 (2012).
[3] C. H. Ahn, J.-M. Triscone, J. Mannhart, Nature 424, 1015 (2003).
[4] H. Yamada, M. Marinova, P. Altuntas, A. Crassous, L. Bégon-Lours, S. Fusil, E. Jacquet, V. Garcia, K. Bouzehouane, A. Gloter, J. E. Villegas, A. Barthélémy, M. Bibes, Scientific Reports 3, 2384 (2013).
[5] M. Marinova, J. E. Rault, A. Gloter, S. Nemsak, G. K. Palsson, J.-P. Rueff, C. S. Fadley, C. Carrétéro, H. Yamada, K. March, V. Garcia, S. Fusil, A. Barthélémy, O. Stéphan, C. Colliex, and M. Bibes, Nano Lett. 15, 2533 (2015).
ES10.7: Correlated Oxides—Interfaces and Magnetism III
Session Chairs
Wednesday PM, April 19, 2017
PCC North, 200 Level, Room 222 A
2:30 PM - *ES10.7.01
Interlayer Coupling in Nickelate-Based Heterostructures
Marta Gibert 1 , Michel Viret 2 , Pavlo Zubko 3 , Nicolas Jaouen 4 , Jean-Marc Tonnerre 5 , Almudena Torres-Pardo 6 , Sara Catalano 1 , Jennifer Fowlie 1 , Alexandre Gloter 7 , Odile Stephan 7 , Jean-Marc Triscone 1
1 , University of Geneva, Geneva Switzerland, 2 , CEA Saclay, L'Orme des Merisiers France, 3 , UCL , London United Kingdom, 4 , SOLEIL, L'Orme des Merisiers France, 5 , Institut Néel, Grenoble France, 6 , Universidad Complutense Madrid, Madrid Spain, 7 , LPS, Orsay France
Show AbstractTransition metal oxides display a wide range of physical properties arising from the complex interplay between their spin, charge, orbital and lattice degrees of freedom. In recent years, complex-oxide heterostructures have garnered much attention due to the many routes they offer for the engineering of novel functionalities and the discovery of fascinating and often unexpected phenomena. The emergence of new phases due to reduced dimensionality or at interfaces between chemically distinct compounds have led to some of the most interesting findings.
We report on how interface engineering can be used to induce a new magnetic phase in the otherwise non-magnetic material LaNiO3 [1]. We show that an induced antiferromagnetic order can be stabilized in LaNiO3 by interfacial coupling to the insulating ferromagnet LaMnO3 in (111)-oriented LaNiO3/LaMnO3 superlattices. The emergent magnetism is used to generate an interlayer magnetic coupling in the heterostructures of a nature that depends on the exact number of LaNiO3 monolayers [2]. For 7-monolayer-thick LaNiO3/LaMnO3 superlattices, negative and positive exchange bias is observed at low temperature before the stabilization of an antiferromagnetically coupled state between the LaMnO3 layers above the blocking temperature. All these behaviours are explained by the onset of an antiferromagnetic spiral order of (1/4, 1/4, 1/4)-wavevector in the ultrathin LaNiO3 layer, akin to that of all other insulating nickelates, and the presence of a structural interface asymmetry with LaMnO3 [3].
[1] Gibert et al., Nat. Mater. 11, 195 (2012).
[2] Gibert et al. Nat. Commun. 7, 11227 (2016).
[3] Gibert et al., Nano Letters 15, 7355 (2015).
3:00 PM - *ES10.7.02
Potential of the LaAlO3/SrTiO3 Interface for Spintronics
D. Vaz 1 , Edouard Lesne 1 , Nicolas Reyren 1 , R. Mattana 1 , F. Choueikani 6 , Henri Jaffres 1 , Eric Jacquet 1 , Rossitza Pentcheva 5 , Y. Fu 2 , M. Jamet 2 , Hiroshi Naganuma 1 3 , J. C. Rojas-Sanchez 1 4 , L. Vila 2 , Manuel Bibes 1 , Agnes Barthelemy 1
1 , Unité Mixte de Physique CNRS-THALES, Palaiseau France, 6 , Synchrotro SOLEIL, Gif sur Yvette France, 5 , University of Duisburg, Duisburg Germany, 2 , CEA-Spintec, Grenoble France, 3 , Tohoku University, Sendai Japan, 4 , Institut Jean Lamour, Nancy France
Show AbstractThe interface formed by an LaAlO3 thin film grown on top of a TiO2-terminated SrTiO3 substrate hosts a two-dimensional electronic system [1]. Although controversy exists regarding some of its physical properties and their precise origin, it is universally found that conductivity only appears beyond an LaAlO3 thickness threshold of 4 unit cells [2] which is a stringent limitation for efficient tunneling application [3]. Through magnetotransport and X-ray absorption spectroscopy experiments, we will show that this critical thickness can be reduced to just one unit cell when a metallic film of cobalt is deposited on top of LaAlO3 [4]. We will demonstrate the generality of the observed onset of conductivity below the critical thickness of LaAlO3 in on Metal/LaAlO3/SrTiO3 heterostructures, as recently predicted by first-principles calculations [5] and in link with the work function of the metal and enthalpy of formation of the oxide [6].
The Rashba spin-orbit coupling present at the interface could be exploit for spin to charge interconversion, which present advantages for future spintronics. We will show spin pumping experiments that evidence a very large spin to charge conversion efficiency of the 2DEG through the inverse Edelstein effect. This effect can be modulated by a gate voltage and its variation is interpreted in terms of a crossover between the occupancy of one to several bands with different orbital characters and different spin-orbit textures [7]. This suggest that oxide interfaces have a strong potential for spintronics, both for the generation or detection of spin currents.
[1] A. Ohtomo, and H. Y. Hwang, Nature 427, 423 (2004).
[2] S. Thiel et al., Science 313, 1942 (2006).
[3] N. Reyren et al., Phys. Rev. Lett. 108, 186802 (2012).
[4] E. Lesne et al.; Nat. Commun. 5, 4291 (2014).
[5] R. Arras et al.; Phys. Rev. B 85, 125404 (2012).
[6] D. Vaz et al.; in preparation
[7] E. Lesne et al.; Nat. Mat. 4726 (2016)
ES10.8: Frontiers in Spintronics II
Session Chairs
Wednesday PM, April 19, 2017
PCC North, 200 Level, Room 222 A
4:30 PM - *ES10.8.01
Spin-Orbit Torques and Magnetoresistance in 5d and 4d Metal Systems
Pietro Gambardella 1
1 Department of Materials, ETH Zurich, Zurich Switzerland
Show AbstractHeterostructures composed of ferromagnetic (FM) and heavy metal (HM) layers have been studied for decades due to their application as perpendicular magnetic recording media. Only recently, however, experiments and theory have evidenced a wide range of magnetotransport phenomena that have little or no counterpart in single FM layers. The absorption and reflection of spin currents induced by spin-orbit coupling in FM/HM bilayers are responsible for the generation of spin-orbit torques (SOT) as well as for unusual magnetoresistive phenomena. The origin of such spin currents is still widely debated. In this talk we will compare the SOT in 5d and 4d metal systems, namely in Co/Pt and Co/Pd bilayers, showing how the reduced bulk spin Hall effect of Pd allows for the detection of interface-related field-like and damping-like SOT, highlighting diverse effects contributing to the total spin current. Further, we will present a comparative study of the spin-orbit torques and magnetoresistance in the linear and nonlinear (current-dependent) regimes. The magnetoresistance of Co/HM bilayers (HM = Ta, W, Pt) is phenomenologically similar to the spin Hall magnetoresistance (SMR) of YIG/Pt, but has a much larger anisotropy, of the order of 0.5 %, which increases with the atomic number of the HM. Additionally, we find a novel magnetoresistance term that is directly proportional to the current and to the transverse component of the magnetization. This so-called unidirectional magnetoresistance changes sign upon inversion of either current or magnetization and correlates with the amplitude of the damping-like SOT.
5:00 PM - ES10.8.02
Heteroepitaxial Ferromagnetic Perovskite Hot-Electron Transistor Down to the Monolayer Limit
Brian Kim 1 , Yasuyuki Hikita 2 , Harold Hwang 2 3
1 Department of Electrical Engineering, Stanford University, Stanford, California, United States, 2 Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California, United States, 3 Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, California, United States
Show AbstractSpintronics has gained much interest for exploring new electronic applications utilizing the spin state of carriers as an additional degree of freedom. In this regard, recent advances in atomic-scale control of perovskite oxide heterostructures provide unique opportunities for integrating a rich variety of interface-induced emergent magnetic phases into spintronics device applications [1]. However, the precise control of coherent spin states in perovskite oxides is obscured by the short spin lifetime and diffusion length in the order of few nanometers [2]. Notably, an atomically thin hot-electron transistor (HET), consisting of semiconductor-emitter / metal-base / semiconductor-collector heterostructures, has natural advantages to overcome the short spin transport parameters [3]. First, the hot-electron transport in the HET is guided in the out-of-plane direction, setting the device length scale comparable to the spin diffusion lengths. Since the device operation is based on hot-electron and not Boltzmann transport, it is immune to fringe field-induced magnetoresistance and Hall effects [4]. Furthermore, inserting a spin-valve in the metal base layer enables spin-filtering by utilizing spin-dependent hot-electron transport [5]. Despite these advantages of HET geometry for spintronics, device development using perovskite oxides has been focused on electric field-effect tuning of the in-plane electronic transport.
In this work, we select atomically thin SrRuO3 (SRO) as the ferromagnetic metal base of the HET. SRO is a promising model system because of its perfect registry with many perovskite oxides, facilitating coherent growth of defect-free heterointerfaces and minimizing the formation of parasitic pinhole defects. As a result, we demonstrate highly reproducible HET operation for SRO thicknesses down to the monolayer limit, controlled with single unit-cell precision (~ 3.9 Å). The hot-electron transfer ratio could be tuned over 4 orders of magnitude by varying the base thickness, and the on/off ratio exceeded 105. The hot electron mean free path in SRO was also deduced with high precision. These results serve as the groundwork for development of perovskite spin transistors in the out-of-plane three terminal geometry.
[1] H. Y. Hwang et al., Emergent phenomena at oxide interfaces. Nature Mater. 11, 103 (2012).
[2] M. Wahler et al., Inverse spin Hall effect in a complex ferromagnetic oxide heterostructures. Sci. Rep. 6, 28727 (2016).
[3] T. Yajima et al., A heteroepitaxial perovskite metal-base transistor. Nature Mater. 10, 198 (2011).
[4] I. Appelbaum et al., Electronic measurement and control of spin transport in silicon. Nature 447, 295 (2007).
[5] D. J. Monsma et al., Perpendicular Hot Electron Spin-Valve Effect in a New Magnetic Field Sensor: The Spin-Valve Transistor. Phys. Rev. Lett. 74, 5260 (1995).
5:15 PM - *ES10.8.03
Thermal Imaging of Spin Peltier Effects
Ken-ichi Uchida 1 2 3
1 , National Institute for Materials Science, Tsukuba Japan, 2 Institute for Materials Research, Tohoku University, Sendai Japan, 3 PRESTO, Japan Science and Technology Agency, Saitama Japan
Show AbstractIn spintronics, a spin counterpart of the Peltier effect was observed by Flipse et al. in 2014 [1]. The "spin Peltier effect" modulates the temperature of a magnetic junction depending on the direction of a spin current. Here we report thermal imaging of the spin Peltier effect [2]; using lock-in thermography technique, we visualize the temperature modulation induced by a spin current injected into a magnetic insulator from an adjacent metal. The thermal images reveal characteristic distribution of spin-current-induced heat sources, resulting in the temperature change confined only in the vicinity of the metal/insulator interface. The finding of this anomalous temperature distribution allows us to estimate the actual magnitude of the temperature modulation induced by the spin Peltier effect, which is found to be more than one order of magnitude greater than that previously believed. In this talk, we will show systematic measurements and numerical simulations of the spin Peltier effect.
[1] J. Flipse et al., Phys. Rev. Lett. 113, 027601 (2014).
[2] S. Daimon, R. Iguchi, T. Hioki, E. Saitoh, and K. Uchida, Nature Commun. 7, 13754 (2016).
5:45 PM - ES10.8.04
Magnetic Backward Diode Exploiting Crossover Spin Valve Action in Manganese Substituted Magnetite/Semiconductor Heterojunctions
Harinath Aireddy 1 , Amal Kumar Das 1
1 , IIT Kharagpur, West Bengal India
Show AbstractWe have studied the electro-magnetic transport properties of Fe3-xMnxO4/p-Si heterostructures (x= 0, 0.25, and 0.5) fabricated by pulsed laser deposition technique. A backward rectifying property and bias voltage dependence of giant junction magnetoresistance (JMR) is observed in the heterostructures. Interestingly, the alternate sign (positive and negative) change of JMR with bias voltage is observed in Fe3-xMnxO4/p-Si heterostructures at room temperature (RT), which (sign change) strickly disappears at lower temperature. Moreover, the JMR is enhanced significantly with increasing the doping concentration of Mn in Fe3-xMnxO4 and found maximum JMR of 90%, 117% and 120% for x = 0, 0.25 and 0.50, respectively at RT. Importantly, the sign inversion of JMR is occured upon Mn substitution in Fe3-xMnxO4 of the heterostructures at higher temperature, but diminishes at lower temperature. The crossover nature of JMR is assigned to the spin polarized transport filtered at the junctions of the heterostructures. These impressive results may have significance to the use of simple devices as silicon-based crossover spin valves and spin filters operating at room temperature in spintronics.
[1] Z. Szotek et al., Phys. Rev. B 74 (2006) 174431.
[2] I. Zutić et al., Rev. Mod. Phy 76 (2004) 323.
[3] S. P. Das et al., Nature (London) 462 (2009) 491.
[4] H. Aireddy et al., Appl.Phys.Lett. 107 (2015) 232406.
[5] H. Aireddy et al., J. Phys. D: Appl. Phys. 49, 415003 (8pp) (2016).
ES10.9: Poster Session II
Session Chairs
Thursday AM, April 20, 2017
Sheraton, Third Level, Phoenix Ballroom
9:00 PM - ES10.9.01
Strain Mediated Large Electro-Mechanical Property of Thin Films
Yanxi Li 1 , Jiefang Li 1 , Dwight Viehland 1
1 Materials Science and Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, United States
Show AbstractBarium titanate (BTO) is a classic perovskite ferroelectric oxide that has attracted much research interest due to its high-dielectric constant and large piezoelectric coefficient. Recently, considerable work has been done on doped BTO systems to further improve its properties. However, researchers need to face the problem of a sharp decrease of its Curie temperature (Cp) after doping.
Here, by utilizing pulsed laser deposition (PLD), high quality epitaxial Sn-doped BTO thin films have been successfully grown on various substrates with different lattice coefficient. The observation of enhanced ferroelectric properties have been found in Sn-doped BTO thin film compared with the bulk ceramics with the same chemical composition. Moreover, with demonstration of successful epitaxial growth, the Cp of these films has been enhanced due to the effect of epitaxial constraint that prevents external dimension changes of the thin film. Moreover, giant piezoelectric coefficients have been obtained from Sn-doped BTO thin film grown on certain substrates by providing a particular strain to the film.
The microstructure of these thin films has been characterized by state-of-the-art electron microscopy to explain the mechanism of the origin of such giant electro-mechanical property of epitaxial thin film. The enhancement of properties for doped BTO thin films would provide many potential application possibilities in multi-functional materials fields.
9:00 PM - ES10.9.02
Expanding Ionic Electrolyte Gating on Oxide Heterostructures by Incorporating Poly-Ionic Liquids with Multifunctional Cation and Anion Groups
Hua Zhou 1 , Yongqi Dong 2 1 4 , Wei Chen 2 , Yu-An Su 2 , Huajun Liu 2 3 , Dillon Fong 2 , Zhenlin Luo 4
1 Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois, United States, 2 Materials Science Division, Argonne National Laboratory, Lemont, Illinois, United States, 4 National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui, China, 3 Institute of Materials Research and Engineering, A*STAR, Singapore Singapore
Show AbstractDue to unique fundamental behaviors of complex oxides, such as the competing and subtle interplay of electronic and magnetic phases, and their sensitivity to defects and doping, external electric fields can be used to craft electronic order, modify chemistry, apply strain, and manipulate spin-orbit couplings. This presents a promising opportunity to create novel functionalities, in principle, enabling device concepts that go far beyond what conventional semiconductor physics allows. In particular, the very high charge density induced by an electric double layer formed at an electrochemical solid-liquid interface has recently been used to induce or “gate” exotic phase transitions, therefore electronic ground states of strongly correlated oxides in the interfacial region, via ‘field-effect doping’. It is highly expected that leveraging ionic electrolyte gating would still be fertile ground for exploration in a broad range of oxides that exhibit novel functionalities. In this talk, we will introduce a new strategy expanding the "knob" of ionic electrolyte gating to induce driven phenomena and control emergent physical properties beyond just conventional field-effect: designing and developing poly-ionic liquid or gel with multifunctional cation/anion groups. The newly developed ionic electrolyte, magnetic semiconducting poly-ionic liquid (msPIL), is a subclass of polyelectrolytes that incorporate magnetic anions in side chains connected through conjugated backbones to form intrinsically photosensitive semiconducting macromolecular architectures (cations). Together with the electrostatic nature, the msPIL/IL mixture forms a unique ionic electrolyte that can be manipulated via photo-excitation, electric field, and magnetic field. Consequently, this will allow us to control the electrical and magnetic transports of oxide heterostructures by photoinduced charge injection and interfacial magnetic proximity effects other than regular electrostatic field effects. We will demonstrate this new strategy of ionic electrolyte gating with two recent experimental progresses. One is to realize rapid resistance switching in perovskite tungstate epitaxial thin films by UV/visible light illumination. The other one is to modulate magnetoresistance and transition temperature of ruthenate perovskite heterostructures via interfacial magnetic electric double layer gating. We believe that creating and utilizing ionic liquids or gels with stimulus response multimodality will open a path toward a new dimension of control of functionality in oxide heterostructures.
9:00 PM - ES10.9.03
Ferroelectric Domain Structure and Photovoltaic Effect in Flexible BiFeO3 Films
Radhe Agarwal 1 , Yogesh Sharma 1 2 , Seungbum Hong 2 , Ram Katiyar 1
1 , University of Puerto Rico, Rio Piedras, San Juan, Puerto Rico, United States, 2 , Argonne National Laboratory, Darien, Illinois, United States
Show AbstractMultiferroic BiFeO3 (BFO) has showed promising potential as photovoltaic material due to its superior ferroelectric properties and optical bandgap which lies in the visible region. Among other wide bandgap ferroelectric photovoltaic (Fe-PV) materials (i.e. BaTiO3, LiNbO3 and Pb(Zr,Ti)O3), BFO exhibits large open circuit voltage (VOC), tunable output, and switchable photovoltaic effect. Herein, we report on structural, ferroelectric, magnetic, and photovoltaic properties of BFO films grown on Copper foil using pulsed laser deposition (PLD) technique. X-ray diffraction, Raman spectroscopy and scanning electron microscopy analysis confirmed the single phase polycrystalline nature and uniform microstructures of these films. Piezoelectric force microscopy (PFM) measurements manifested the formation of layered domain growth in step bunching fashion with random orientations. We observed weak ferromagnetic behavior with out-of-plane magnetic moment of ~30 emu/cm3. A distinct photovoltaic (PV) behavior was noted under white-light illumination with an open circuit voltage (VOC) ~0.23 V and short circuit current (JSC) ~112 µA/cm2, respectively. Time dependent VOC and JSC measurements also showed well-defined retention of photocurrent and photovoltage over multiple on and off illumination cycles.
9:00 PM - ES10.9.04
Improved Dielectric Properties of (Ba,Sr)TiO3-Ba4Ti13O30 Composite Ceramics for Tunable Microwave Devices
Rui Zheng 1 , Dengren Jin 1
1 , Shanghai University, Shanghai China
Show Abstract
(Ba,Sr)TiO3-Ba4Ti13O30 composite ceramics were synthesized by a modified solid state sintering method using mixed-phase of TiO2, BaTiO3 and SrTiO3. The phase structure, microstructure and dielectric properties of the composite ceramics were investigated. It is found that with the increase of Ba4Ti13O30, the dielectric constant and loss tangent significantly decreased, and the tunability is still remained to a certain extent. Results shows that (Ba,Sr)TiO3-Ba4Ti13O30 composite ceramics sintered at 1200oC exhibited excellent comprehensive performance. Especially, as the molar percentage of TiO2 increased up to 60% in the green pellet, (Ba,Sr)TiO3-Ba4Ti13O30 composite ceramics has the dielectric constant of 89, loss tangent of 0.6% (at ~1MHz) and tunability of 3% (under 10 kV/cm biasing), respectively. So (Ba,Sr)TiO3-Ba4Ti13O30 composite ceramics are promising materials for tunable microwave device applications.
Keywords: (Ba,Sr)TiO3-Ba4Ti13O30, Microstructure, Dielectric properties, Tunabilities
9:00 PM - ES10.9.05
Fabrication and Characterization of La, Ga Co-Modified BiFeO3-PbTiO3 Multiferroic Ceramics with High Magnetic Field Assisted Sintering
Shujin Shen 1 , Jinrong Cheng 1
1 School of Materials Science and Engineering, Shanghai University, Shanghai China
Show AbstractThe BiFeO3-PbTiO3 (BF-PT) multiferroic ceramics has attracted broad attention due to the excellent performance and a wide range of potential applications. However, it is crucial to apply a favorable synthesis and sintering method in the process of ceramics preparation. Up to date, there is rarely any report on the effect of high magnetic field assisted sintering on BF-PT based samples.
In this work, the polycrystalline 0.57(Bi0.8La0.2)(Ga0.05Fe0.95)O3-0.43PbTiO3 (BLGF-PT) ceramics were prepared by the solid-state reaction method, whose calcination and sintering process were carried out under the magnetic field from 0 T to 8 T. The effect of magnetic field intensity on the phase structure, grain size, dielectric and piezoelectric properties of BLGF-PT were investigated systematically. The results indicate that the high magnetic field assisted sintering exerts considerable impact on the structure and performance of ceramics. BLGF-PT ceramics exhibit the more densified microstructure after sintering under the high magnetic field of 8 T (Figure 1). The magnetic field assisted sintered BLGF-PT ceramics have the dielectric loss of 0.03 at the frequency of 100 Hz, much lower than that of 0.16 for the specimen without using the magnetic assisted sintering. Furthermore, the BLGF-PT ceramics sintered under the high magnetic fields exhibit the enhanced dielectric, ferroelectric, and piezoelectric properties. Our results indicate that the high magnetic field assisted heat treatment is a promising technology to improve some crucial properties of BLGF-PT ceramics.
9:00 PM - ES10.9.06
Probing the Tip Induced Polarization Switching and Magnetoelectric Coupling in PFN/NZFO/PFN Heteterostructure at Room Temperature
Dhiren Pradhan 1 , Shalini Kumari 1 , Rama Vasudevan 2 , Aswini Pradhan 3 , Sergei Kalinin 2 , Ram Katiyar 1
1 , University of Puerto Rico, San Juan, Puerto Rico, United States, 2 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 3 , Norfolk State University, Norfolk, Virginia, United States
Show AbstractMultiferroic Magnetoelectrics (MF-ME) have attracted considerable attention since its rediscoveries as possible candidates for a wide variety of future microelectronic and memory devices, although robust magnetoelectric (ME) coupling between electric and magnetic orders at room temperature still remains difficult to achieve. In continuation to our investigations for achieving robust ME coupling at room temperature we have studied FE/FM/FE trilayer heterostructure. Here we report the tip induced polarization switching and ME properties of Pb(Fe0.5Nb0.5)O3/Ni0.65Zn0.35Fe2O4/Pb(Fe0.5Nb0.5)O3 (PFN/NZFO/PFN) trilayer nanoscale heterostructure having dimension 70/20/70 nm, respectively at room temperature. The presence of only (00l) reflection of PFN and NZFO in the XRD patterns and electron diffraction patterns in TEM confirm the epitaxial growth of multilayer heterostructure. The existence of ferroelectricity and tip induced polarization switching at nanoscale has been confirmed by band excitation piezo force microscopy (BE-PFM) studies. The distribution of the ferroelectric loop area in a wide area has been studied, suggesting that spatial variability of ferroelectric switching behaviour is low, and film growth is of high quality. The ferroelectric and magnetic phase transitions of these heterostructures have been found at ~575 K and ~650 K, respectively which are well above room temperature. These nanostructures exhibit low loss tangent, large saturation polarization (Ps ~ 38µC/cm2) and magnetization (Ms ~ 48 emu/cm3) with strong ME coupling at room temperature elucidate the possible potential candidates for multifunctional and spintronics nanoscale device applications.
9:00 PM - ES10.9.07
Hydrothermal Synthesize of Ferroelectric Oxide Heterostructures with Sharp Interfaces
Ming Li 1 , Zhaohui Ren 1 , He Tian 1 , Gaorong Han 1
1 School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang Province, China
Show AbstractHeterostructure systems in which materials of different compositions meet at the interfaces have attracted intensive attention in materials science during recent decades. They are expected to greatly influence the design and development of materials with defined functionality. Many new concepts have been proposed for controlling the synthesis of such heterostructure materials as semiconductor, metallic and oxide heterostructures. Moreover, it is highly expected to explore new methods to prepare heterostructure with sharp interface. Here, we have developed a facile hydrothermal preparation of oxide heterostructures with sharp and coherent interfaces, and the heterostructured oxide composites show an intriguing interface microstructure and photocatalytic activity.
9:00 PM - ES10.9.08
Resonant and Non-Resonant Raman Spectroscopy of Nickel Oxide Crystals and Thin Films
Ece Aytan 1 , Monica Lacerda 3 2 , Rameez Samnakay 1 , Junxue Li 4 , Bishwajit Debnath 3 , Shanshan Su 3 , Tonmoy Kumar Bhowmick 3 , Roger Lake 3 , Jing Shi 4 , Fariborz Kargar 3 , Alexander Balandin 3 1
1 Material Science and Engineering, University of California Riverside, Riverside, California, United States, 3 Electrical and Computer Engineering, University of California Riverside, Riverside, California, United States, 2 Polo Xerém, Universidade Federal do Rio de Janeiro, Rio de Janeiro Brazil, 4 Physics and Astronomy, University of California Riverside, Riverside, California, United States
Show AbstractNickel Oxide (NiO) is an antiferromagnetic insulator material with crystalline structure consisting of ferromagnetically aligned (111) planes, which are anti-ferromagnetically aligned with respect to each other. This material has recently attracted significant attention owing to proposals for spintronic applications in THz frequency regime. Raman spectroscopy can provide valuable information on the phonon and magnon states in such materials, and can possibly shed light on specifics of the phonon – magnon interactions. Here, we report results of a comparative Raman spectroscopic investigation of NiO bulk crystals and NiO thin films under ultraviolet (UV) and visible laser excitations. The measurements were conducted in the backscattering configuration under the laser excitation wavelength of 325 nm (resonant) and 488 nm (non-resonant). It was established that the two-magnon band at 1496 1/cm in visible Raman spectrum, originating from the Brillouin zone boundary magnons, is strongly suppressed in UV Raman spectrum. The phonon signatures in the UV Raman spectrum are closer to the calculated phonon energies and dispersion obtained from neutron scattering. The suppression of the magnon signatures in UV Raman spectrum was attributed to the resonant light absorption and reduction of the interaction volume. The temperature dependent measurements were used for verification of the magnon band assignment. All temperature measurements were performed under argon atmosphere to ensure that no surface oxidation occurs. Our results suggest that combined UV and visible Raman spectroscopy can help in understanding magnon – phonon interaction processes in NiO. This work was supported as part of the Spins and Heat in Nanoscale Electronic Systems (SHINES), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences (BES) under Award # SC0012670.
9:00 PM - ES10.9.09
Reversible Control of the Magnetization in Iron Based Magnetic Oxides via Lithium Ions
Guodong Wei 1 , Yanxue Chen 1
1 , Shandong University, Jinan China
Show AbstractIn this work, reversible control of the saturated magnetization of iron based magnetic oxides by Li ions is demonstrated. miniature Li batteries were assembled using different iron based magnetic oxides as the active cathode. A stable magnetism modulation is realized by a nondestructive electrochemical process in which the lithium insertion results in a valence change and partial redistribution of Fe3+ cations in the crystal structure. The relation between the battery voltage and the chemical phases were studied by ex situ X-ray diffraction and in situ magnetic measurement. In a suitable discharge potential range, a reversible control of the saturated magnetization was obtained without any structural damage to the magnetic electrode. By further optimizing the cell performance, a large reversible change in magnetization more than 10% has be realized at room temperature, suggesting this work has a potential for future practical applications.
Symposium Organizers
John Heron, University of Michigan
Satoshi Okamoto, Oak Ridge National Laboratory
Morgan Trassin, ETH Zürich
Pu Yu, Tsinghua University
Symposium Support
CrysTec Gmbh
Lake Shore Cryotronics Inc
NT-MDT America Inc.
Radiant Technologies, Inc
Twente Solid State Technology B.V.
ES10.10: Composite Multiferroics—Electric Field Control of Magnetism and Magnetoelectric Interfaces I
Session Chairs
John Heron
Sebastiaan van Dijken
Thursday AM, April 20, 2017
PCC North, 200 Level, Room 222 A
9:00 AM - *ES10.10.01
Device Applications of Acoustically Drive Ferromangetic Resonance in Synthetic Multiferroic Heterostructures
Sayeef Salahuddin 1 , Dominic Labanowski 1
1 , University of California, Berkeley, Berkeley, California, United States
Show AbstractRecent experiments [1] have demonstrated that it is possible to excite a ferromagnetic resonance by a travelling sound waves in a synthetic multiferroic heterotstructure. This acoustically-driven ferromagnetic resonance operates by coupling the dynamic strain, exerted by the sound wave in a piezoelecric material, on to a magnetoelastic ferromagnet sitting on top. The magnetoelectric coupling converts the dynamic strain into an alternating `magnetic field', eventually leading the ferromagnets into resonance under appropriate conditoins. Our previous quantitative measurements of this phenomenon have shown [2] that it is possible to obtain extremely high coupling efficiency (>99.9%) of the travelling acoustic wave into a thin ferromagnetic layer. This high coupling, observable at GHz frequencies in sub-mm magnetic films, opens up opportunities for a number of device applications with improved functionality compared to the state of the art.
[1]M.Weiler, L. Dreher, C. Heeg, H. Huebl, R. Gross, M. S. Brandt, and S. T. B. Goennenwein, Phys. Rev. Lett. 106, 117601 (2011)
[2] Labanowski, Jung, Salahuddin, Applied Physics Letters, 108, 022905 (2016).
9:30 AM - ES10.10.02
On the Speed of Piezostrain-Mediated Voltage-Driven Perpendicular Magnetization Reversal—A Computational Perspective
Renci Peng 1 2 , Jiamian Hu 2 , Long-Qing Chen 1 2 , Ce-Wen Nan 1
1 School of Materials Science and Engineering, Tsinghua University, Beijing China, 2 Department of Materials Science and Engineering, Pennsylvania State University, State College, Pennsylvania, United States
Show AbstractBy linking the dynamics of local piezostrain to the dynamics of local magnetization, we computationally analyze the speed of a recently proposed scheme of piezostrain-mediated perpendicular magnetization reversal driven by a voltage pulse [Hu et al., Nano Lett. 15, 616 (2015)] in magnetoelectric heterostructures. The model heterostructure utilized here consists of an ellipse-shaped ultrathin amorphous Co20Fe60B20 on top of a polycrystalline Pb(Zr,Ti)O3 (PZT) thin film. A diagram showing the speed of perpendicular magnetization reversal as a function of the magnitude of applied voltage pulse and the stiffness damping coefficient of PZT film is established. The analyses suggest that the speed ranges approximately from 2.5 ns to 5.5 ns when the magnitudes of driving voltages are below 1 V, and that the energy dissipation is at the level of femtoJoule. These analyses can be adapted to analyze the response time of other piezostrain-enabled spintronic devices.
9:45 AM - *ES10.10.03
Magnetism and Spin Transport in Ferreoelectric/Ferromagnetic Heterostructure
Jingsheng Chen 1
1 Department of Materials Science and Engineering, National University of Singapore, Singapore, Singapore, Singapore
Show AbstractUsing the electric method to manipulate the magnetism is of great interest to fundamental physics as well as technological point of view, which enable the possibility to achieve magnetic logic and memory devices with low power consumption. One of the main means is fabricating the artificial composite multiferroics, which combines the ferroelectric and magnetic constituents, to utilize the interface coupling, including charge modulation, the orbital reconstruction due to the ions displacement and magnetic order reconstruction. In order for the investigation of ferroelectric polarization effect on the magnetism and spin transport properties it is therefore essential to control the self-polarization of ferroelectric thin film. We have found that the self-polarization of BaTiO3 (BTO) thin films depends on both the interface termination of SrTiO3 (STO) substrate and the flexoelectric effects. When the film is fully strained, the interface termination of SrTiO3 is the dominating factor. The polarization is pointed upward and downward, respectively when BTO films are grown on SrO - terminated and TiO2-terminated STO substrates, respectively. With increase of the film thickness above 15 nm, the strain of BTO film arising from STO substrates starts to relax, and the flexoelectric effect becomes dominating which favors the self-polarization to be upward. The magnetic properties of 5 unit cell La0.7Sr0.3MnO3 (LSMO) layer grown on BTO films with different polarization direction were investigated. It was found that saturation magnetization of LSMO films grown on BTO with polarization up is much larger than that of LSMO grown on BTO with polarization down. XAS and XMCD investigation showed that magnetism of Ti atoms in BTO was induced. Furthermore, the Ti atoms are ferromagnetically and antiferromagnetically coupled to Mn atoms for different ferroelectric terminations. The effect of ferroelectric polarization on the damping constant of LSMO were also investigated by angle resolved FMR technique. The damping constant in the order of magnitude of 10-4 was obtained.
10:15 AM - ES10.10.04
Electric Field Control of Magnetic Skyrmions in Magnetoelectric Nanostructures
Jiamian Hu 1 , Tiannan Yang 1 , Long-Qing Chen 1
1 Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractAn ultrathin ferromagnetic metal with a heavy-metal underlayer (the atoms of which exhibit strong spin-orbit coupling) can possess an unconventional non-collinear spin-spin exchange interaction (namely, Dzyaloshinskii-Moriya interaction). It is the interplay among such non-collinear exchange interaction, the conventional collinear (Heisenberg-type) exchange interaction, and the magnetic dipole-dipole interaction that leads to the formation of a magnetic skyrmion. Using an electric field to modulate the spin structure of a magnetic skyrmion would dissipate much less heat than using an electric current, and therefore can be potentially utilized to design energy-efficient skyrmion-based spintronics. However, relevant reports have remained scarce. In this talk, I will introduce our very recent computational prediction of electrically controlled magnetic skyrmions in an ultrathin amorphous Co20Fe60B20 nanomagnet, achieved by electrically driving a juxtaposed polycrystalline Pb(Zr,Ti)O3 (PZT) film. Local piezostrains on the PZT film surface can be transferred to the Co20Fe60B20 across the interfaces and then modify the spin structure. It was found that applying a small out-of-plane voltage across the PZT film could toggle the spin structure between an isolated magnetic skyrmion and a single-domain ferromagnet. These results may provide a new route to design energy-efficient skrymion-based spintronic devices.
10:30 AM - ES10.10.05
Deterministic Control of Cationic Substitution by Strain in Bi4Ti3O12-BiFeO3 Epitaxial Thin Films
Changhee Sohn 1 , Dongkyu Lee 1 , Xiang Gao 1 , Ho Nyung Lee 1
1 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractStrain engineering, a conventional way to mechanically tune the structure of a thin film, is known to be a powerful means to improve or to develop novel functionalities of materials. Here, we attest the theoretically predicted strain control of preferential cationic substitution of the multiferroic BiFeO3 for building blocks in the ferroelectric Bi4Ti3O12 [A. Y. Birenbaum and C. Ederer, Appl. Phys. Lett. 108, 082903 (2016)]. Pulsed laser epitaxy was employed to digitally control the compositional substitution by precisely controlling the growth rate of both oxides. In bulk cases, it is known that Bi4Ti3O12-BiFeO3 (BTFO) is a well-known ferroelectric material with layered Aurivillius structure where Ti and Fe ions are rather randomly distributed. Intriguingly, the above mentioned density functional theory calculations showed a possibility of site specific substitution of Fe for Ti by epitaxial strain. We have fabricated BTFO epitaxial films on various substrates (including SrTiO3, LSAT, and LaAlO3) to control the sign and degree of strain. BTFO thin films with different cation ratios (Fe/Ti) were prepared to check whether the Fe substitution for Ti is site specific or random. Details on structure, microstructure, magnetic, and ferroelectric investigations were performed and will be presented based on results from a systematic investigation with x-ray diffraction, scanning transmission electron microscopy/electron energy loss spectroscopy, and magnetic and ferroelectric characterization.
This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.
10:45 AM - ES10.10.06
Probing the Depth Dependent Magnetization of FeGa/NiFe Multilayers Using Polarized Neutron Reflectometry
Colin Rementer 1 , Michelle Jamer 2 , Julie Borchers 2 , Alexander Grutter 2 , Brian Kirby 2 , Qiang Xu 1 , Paul Nordeen 1 , Gregory Carman 1 , Yuanxun Wang 1 , Jane Chang 1
1 , University of California Los Angeles, Los Angeles, California, United States, 2 , NIST, Gaithersburg, Maryland, United States
Show AbstractThere is a growing interest in developing magnetostrictive compounds for micro actuators and novel RF magnetic devices to replace Terfenol-D, as it is difficult to fabricate and contains rare earth materials. Galfenol, FexGa (x = 75-85), is the most prominent alternative due to its large magnetostriction (>200 ppm), high piezomagnetic coefficient (3 ppm/Oe), and high stiffness (70 GPa).1 In previous research, FexGa and NiFe were deposited in a multilayer heterostructure in order to exchange couple the two layers, thereby improving the properties of the galfenol layer while maintaining the magnetostrictive integrity.2 In this work, multilayer laminates were fabricated with Fe86Ga14 and Ni81Fe19 on piezoelectric PMN-PT [011] in order to explore voltage control of the magnetization. Using SQUID magnetometry with in situ poling, it was found that straining the substrate with 400 V in remnant magnetic field strains the multilayer enough to induce a significant change in anisotropy. To understand how this effect varies with proximity to the piezoelectric substrate, polarized neutron reflectometry was used to determine the depth profiles of the structure and in-plane vector magnetization as functions of applied magnetic field and voltage. The laminates are insensitive to any structural changes with voltage, but there are pronounced magnetic changes. Application of 400 V results in an enormous increase in spin-flip scattering, unambiguously demonstrating a substantial rotation of the magnetization perpendicular to the applied magnetic field direction. Model fitting of the data suggests that the effect is indeed depth dependent, with increased magnetization rotation for layers nearer the substrate interface. Results for a series of multilayers with different layer thicknesses will be discussed. These measurements thus provide direct evidence of a voltage-induced rotation of the both the NiFe and FeGa magnetization as well as a means to separate the response of the magnetostrictive and soft layer components.
ES10.11: Multiferroics and Magnetoelectrics—Properties of Thin-Films
Session Chairs
Jingsheng Chen
Sayeef Salahuddin
Thursday PM, April 20, 2017
PCC North, 200 Level, Room 222 A
11:30 AM - ES10.11.01
Magnetic and Dielectric Properties in Room-Temperature Multiferroic GaxFe2-xO3 Epitaxial Thin Films
Tsukasa Katayama 1 , Yosuke Hamasaki 1 , Shintaro Yasui 1 , Mitsuru Itoh 1
1 , Tokyo Institute of Technology, Kanagawa-ken Japan
Show AbstractMultiferroic materials which possess both ferroelectric and ferromagnetic characteristics in single phase have attracted considerable attentions. However, such multiferroicity is usually observed only at low-temperature, leading to a high demand for room-temperature multiferroic material. GaxFe2-xO3-type iron oxide thin film is one of promising candidates of room-temperature multiferroic materials because of its large magnetization [1-3]. GaxFe2-xO3 thin film exhibits both ferroelectricity and ferrimagneticity along the b and c-axes at room temperature, respectively, and shows large magnetoelectric features [1-3]. To realize large magnetoelectric properties and application of GaxFe2-xO3 films, controlling of their ferroelectric and ferrimagnetic properties at room-temperature are crucial. Thus, systematic investigation of multiferroicity as a function of compositional ratio of Ga and Fe is important for fundamental understanding and future applications. In this study, we fabricated high-quality GaxFe2-xO3 epitaxial thin films (x = 0.0–1.0) and systematically investigated their ferroelectric and ferrimagnetic properties. We found that all films exhibit ferroelectricity at room temperature and coercive electric field (Ec) can be widely controlled in a range of 800–3700 kV/cm by changing x and film thickness. For the magnetic properties, we found that coercive magnetic field (Hc) decreases but saturated magnetization (Ms) increases with increasing x at 0 ≤ x ≤ 0.5. On the other hand, at 0.5 ≤ x ≤ 1, Hc shows constant value while Ms decreases with increasing x, according to the site of Ga ions. Finally, we demonstrated room-temperature magnetocapacitance effects of the GaxFe2-xO3 films.
[1] S. Mukherjee et al., Phys. Rev. Lett. 111, 087601 (2013). [2] S. H. Oh et al., Appl. Phys. Lett. 106, 142902 (2015). [3] T. Arima et al., Phys. Rev. B 70, 064426 (2004).
11:45 AM - *ES10.11.02
Non-Collinear Spin Order in BiFeO3—Tuning, Control and Imaging
Manuel Bibes 1
1 , CNRS-Thales, Palaiseau France
Show AbstractIn multiferroic materials, the coexistence of several exchange interactions often results in competition between non-collinear spin orders which are sensitive to temperature, hydrostatic pressure, or magnetic field. Here, we will show how in bismuth ferrite (BiFeO3), a room-temperature multiferroic, the intricacy of the magnetic phase diagram is only fully revealed in thin films:1 epitaxial strain suppresses the cycloidal spin order present in the bulk,2 transforming it into various antiferromagnetic states, modifying the spin direction and ordering patterns.3 We will report the combined effect of strain and magnetic field on the spin order in BiFeO3 and, through nuclear resonant scattering4 and Raman spectroscopy, show that both strain and magnetic field destabilize the cycloid, resulting in a critical field sharply reduced from the bulk value. Finally, we will introduce an innovative non-invasive scanning magnetometry technique to reveal the spin cycloid in real-space.
1 D. Sando, A. Barthélémy, and M. Bibes, J. Phys. Condens. Matter 26, 473201 (2014).
2 I. Sosnowska, T. Peterlin-Neumaier, and E. Steichele, J. Phys. C 15, 4835 (1982).
3 D. Sando et al, Nature Mater. 12, 641 (2013).
4 R. Röhlsberger et al, Phys. Rev. B 67, 1 (2003).
This research received support from ERC Consolidator grant MINT #615759 and ERC Starting grant IMAGINE.
12:15 PM - ES10.11.03
Controlling the Electrical and Magnetoelectric Properties of Epitaxially Strained Sr1-xBaxMnO3 Thin Films
Eric Langenberg 1 2 , Laura Maurel 3 2 , Roger Guzman 3 4 , Veronica Goian 5 , Noelia Marcano 1 6 , Thomas Prokscha 7 , Pedro Algarabel 1 2 , Cesar Magen 4 3 8 , Stanislav Kamba 5 , Jose Pardo 3 4 9
1 , Instituto de Ciencia de Materiales de Aragón (ICMA), Universidad de Zaragoza-CSIC, Zaragoza Spain, 2 Física de la Materia Condensada, Universidad de Zaragoza, Zaragoza Spain, 3 , Instituto de Nanociencia de Aragón (INA), Universidad de Zaragoza, Zaragoza Spain, 4 , Laboratorio de Microscopías Avanzadas, Universidad de Zaragoza, Zaragoza Spain, 5 , Institute of Physics, Czech Academy of Sciences, Prague Czech Republic, 6 , Centro Universitario de la Defensa, Academia General Militar, Zaragoza Spain, 7 , Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, Villigen Switzerland, 8 , Fundación ARAID, Zaragoza Spain, 9 Ciencia y Tecnología de Materiales y Fluidos, Universidad de Zaragoza, Zaragoza Spain
Show AbstractThe strong coupling in perovskite (Sr,Ba)MnO3 system between polar instability, spin order and lattice makes epitaxial films of these compounds to become ideal candidates for tailoring electrical and magnetoelectric properties through the accurate control of Ba-content and epitaxial strain. Here, first, polar order is proved to be induced in Sr1-xBaxMnO3 thin films by expanding the lattice either by epitaxial strain or chemical pressure, which correlates with the evolution of the dielectric properties. Second, spin-phonon coupling is investigated, in which a clear hardening of the lowest-frequency polar phonon is found around the Néel temperature. A large magnetoelectric response is found in (Sr,Ba)MnO3 system, in which the dielectric constant drops up to 50% when the antiferromagnetic order emerges, greatly overcoming most so-far-known magnetoelectric oxides. More important, this coupling between magnetism and dielectric properties can be tuned from ~18% to ~50% by appropriately selecting both Ba-content and epitaxial strain. Third, a clear tendency to increase the band gap energy on increasing the unit cell volume either by epitaxial strain or chemical pressure is found, which opens the way for engineering the semiconducting properties of (Sr,Ba)MnO3 system at will. Thus, this work proves the possibility to design the electrical response and the magnetoelectric coupling in (Sr,Ba)MnO3 system.
12:30 PM - ES10.11.04
Oxygen-Vacancy Engineering in Strained Multiferroic SrMnO3 Thin Films
Laura Maurel 1 2 3 , Eric Langenberg 3 4 5 , Roger Guzman 6 7 , Cesar Magen 6 3 8 , Pedro Algarabel 3 4 , Jose Pardo 2 6 9
1 Laboratory for Mesoscopic Systems, Paul Scherrer Institut, Villigen Switzerland, 2 Instituto de Nanociencia de Aragón, Universidad de Zaragoza, Zaragoza Spain, 3 Departamento de Física de la Materia Condensada, Universidad de Zaragoza, Zaragoza Spain, 4 Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza-CSIC, Zaragoza Spain, 5 Department of Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 6 Laboratorio de Microscopías Avanzadas, INA-Universidad de Zaragoza, Zaragoza Spain, 7 Institut de Ciencia de Materiales de Barcelona, ICMAB-CSIC, Bellaterra Spain, 8 , Fundación ARAID, Zaragoza Spain, 9 Departamento de Ciencia y Tecnología de Materiales y Fluidos, Universidad de Zaragoza, Zaragoza Spain
Show AbstractThe urge to bend conventional rules in developing multiferroic materials with strong magnetoelectric coupling has been partially solved by strain engineering. Among these novel strain-induced multiferroic materials, SrMnO3 was proposed as an optimal candidate [1] as strain promotes the polar distortion and associated off-centering of the magnetic Mn atoms. The prediction of the polar instability under epitaxial strain was successfully verified and shown to be concomitant with the emergence of conduction domains [2].
However, the properties of these thin films not only depend on the imposed strain but also on the mechanism to accommodate the in-plane lattice parameter, being off-stoichiometry an additional mechanism besides the widely-known modification of the bond lengths or the octahedral tilts in stoichiometric perovskites.
Here we show experimental evidence for the previously proposed [3] increase of the oxygen vacancy content on increasing tensile epitaxial strain. Furthermore, a novel dependence of the oxygen stoichiometry on the film thickness has been found, allowing us to control the concentration of these defects by both the applied strain and film thickness. The control of the oxygen vacancies content in magnetoelectric oxides opens new routes to induce unexpected properties in strained thin films. In this presentation we analyze the effect of the oxygen-vacancy content on the ferroic properties of strained SrMnO3 films focusing on the generation of a flexoelectric component that rotates the in-plane <110> ferroelectric polarization [4].
References
[1] J. H. Lee and K. M. Rabe, Phys. Rev. Lett. 104, 207204 (2010)
[2] C. Becher et al., Nature Nanotechnol. 10, 661 (2015)
[3] U. Aschauer et al., Phys. Rev. B 88, 054111 (2013)
[4] R. Guzmán et al., Nano Lett. 16, 2221 (2016)
12:45 PM - ES10.11.05
Magnetoelectricity at the Antiperovskite/Perovskite Interface
Ding-Fu Shao 1 , Tula Paudel 1 , Evgeny Tsymbal 1
1 Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, Nebraska, United States
Show AbstractComplex oxide materials with the perovskite crystal structure (ABO3) are known for their interesting macroscopic physical properties involving the interplay between magnetism, ferroelectricity, and conductivity. Much less explored are the antiperovskite compounds (AXM3) where the atomic positions of cations and anions are inverted creating unique, wide-ranging properties different from perovskites. For example, it has been demonstrated that antiperovskite materials may exhibit superconductivity, negative thermal expansion, and magnetoresistance. Moreover, theoretical predictions suggest that some of the antiperovskites reveal topologically non-trivial behavior. Due to the structural similarity, interfaces combining perovskite and antiperovskite compounds can be fabricated and are expected to form a new playground for materials design, where the coupling across the interface may lead to new fundamental properties and functional behavior. Here, based on first-principles density-functional calculations, we explore the magnetoelectric effect at the (001) interface between antiperovskite GaNMn3 and perovskite ATiO3 (A = Sr and Ba). Bulk GaNMn3 is an antiferromagnetic material with the magnetic moments of the Mn ions lying in the (111) planes, forming compensating non-collinear spin configurations with a zero net magnetization ground state. Our calculations predict that different from the Γ5g non-collinear magnetism of the bulk GaNMn3, strong magnetic moment enhancement and reorientation emerge at the interface resulting in the sizable net magnetization pointing along the [110] direction. Moreover, we find that switching of the ferroelectric polarization of BaTiO3 drives the reversal of the net magnetization of GaNMn3. This phenomenon occurs due to the effect of ferroelectric polarization on the magnitude of the antiferromagnetic coupling between the nearest Mn atoms at the interface. Reversal of magnetization by electric means is the holy grail of voltage-controlled spintronics, and thus our results pave a new route to achieve this functionality by exploiting antiperovskite/perovskite interfaces.
ES10.12: Complex Oxides—MITs
Session Chairs
Thursday PM, April 20, 2017
PCC North, 200 Level, Room 222 A
2:30 PM - ES10.12.01
Nanoscale Resistive Domains Imaging across a Metal-to-Insulator Transition in NdNiO3
Daniele Preziosi 1 , Laura Lopez-Mir 2 , Bouzehouane Karim 1 , Manuel Bibes 1
1 , UMR137-CNRS/Thales, Palaiseau France, 2 , Centre d’Investigació en Nanociència i Nanotecnologia, Barcellona Spain
Show AbstractPerovskite rare-earth nickelates (ReNiO3) have emerged as fundamental bricks in specific oxide heterostructures [1] to obtain novel magnetic phases for the next generation of oxide electronics and spintronics. The control over the interplay between electronic correlations and charge transfer effects can lead to a spin and/or orbital polarization [2,3,4]. A hallmark feature of nickelates that still requires a detailed understanding is the metal-to-insulator transition (MIT). The MIT has been mainly studied via macroscopic transport measurements and, only recently, microscopically by a synchrotron-based experiment [5]. The nanoscale approach can guarantee access to information such as inhomogeneity of the material and combination of local strain/distortions. In this regard, we have used a conductive-atomic force microscopy technique (C-AFM) to study at the nanoscale level the formation of the resistive domains in NdNiO3 thin films grown onto LaAlO3 single crystals by pulsed-laser deposition. We will show mappings of the real-space distribution of metallic and insulating regions characterizing the onset of the MIT in both cooling and warming processes allowing a comparison with acquired macroscopic transport measurements and elsewhere reported microscopic characterization of the metallic/insulating domains [5].
[1] Grisolia, M .N., et al., Nature Physics 12, 484-492 (2016)
[2] Boris, A.V., et al., Science 332, 937(2011)
[3] Chen, H. et al., PRL 110, 186402 (2013)
[4] Disa, et al., PRL 114, 026801 (2015)
[5] Mattoni, G., et al., arXiv :1602.04445v1 (2016)
This work was supported by the ‘MINT’ ERC Consolidator Grant #615759.
2:45 PM - *ES10.12.02
Understanding Nanoscale Heterogeneity and Phase Coexistence in Quantum Materials
Elke Arenholz 1
1 , Lawrence Berkeley National Lab, Berkeley, California, United States
Show AbstractHeterogeneity of quantum materials on the nanoscale can result from the spontaneous formation of regions with distinct atomic, electronic and/or magnetic order, and indicates coexistence of competing quantum phases. In complex oxides, the subtle interplay of lattice, charge, orbital, and spin degrees of freedom gives rise to especially rich phase diagrams. For example, coexisting conducting and insulating phases can occur near metal-insulator transitions, colossal magnetoresistance can emerge where ferromagnetic and antiferromagnetic domains compete, and charge-ordered and superconducting regions are present simultaneously in materials exhibiting high-temperature superconductivity. Additionally, externally applied fields (electric, magnetic, or strain) or other external excitations (light or heat) can tip the energy balance towards one phase, or support heterogeneity and phase coexistence and provide the means to perturb and tailor quantum heterogeneity at the nanoscale.
Engineering nanomaterials, with structural, electronic and magnetic characteristics beyond what is found in bulk materials, is possible today through the technique of thin film epitaxy, effectively a method of ‘spray painting’ atoms on single crystalline substrates to create precisely customized layered structures with atomic arrangements defined by the underlying substrate. Charge transfer and spin polarization across interfaces as well as imprinting nanoscale heterogeneity between adjacent layers lead to intriguing and important new phenomena testing our understanding of basic physics and creating new functionalities. Moreover, the abrupt change of orientation of an order parameter between nanoscale domains can lead to unique phases that are localized at domain walls, including conducting domain walls in insulating ferroelectrics, and ferromagnetic domain walls in antiferromagnets.
Here we present our recent results on tailoring the electronic anisotropy of multiferroic heterostructures by imprinting the BiFeO3 domain pattern in an adjacent La0.7Sr0.3MnO3 layer [1], understanding the metal-insulator transition in strained VO2 thin films [2] and identifying a three-dimensional quasi-long-range electronic supermodulation in YBa2Cu3O7-x/La0.7Ca0.3MnO3 heterostructures [3].
References
[1] C. Ju et al., Adv. Mater. 28, 876 (2016).
[2] A.X. Gray et al., Phys. Rev. Lett. 116, 116403 (2016).
[3] J. He et al., Nat. Commun. 7, 10852 (2016).
3:15 PM - ES10.12.03
Engineering One-Dimensional Quantum Stripes from Layered Complex-Oxides
Ambrose Seo 1
1 , University of Kentucky, Lexington, Kentucky, United States
Show AbstractOne-dimensional (1D) systems offer an important platform for studying low-dimensional phenomena often associated with the onset of critical quantum phase transitions, such as charge/spin density waves, topological edge and surface states, and spin/charge/orbital fractionalization, to name a few. While exactly solvable models, such as Luttinger liquid theory, are thought to describe 1D systems very well, only a few naturally occurring materials with intrinsic 1D structure are available for experimental verification.
Here we present a new approach of synthesizing 1D quantum systems by creating dimensionally-confined stripe-superlattices from in-plane oriented 2D layered crystals. We have used this method to synthesize 1D IrO2 stripes using a-axis oriented superlattices of Sr2IrO4 and the wide bandgap insulator (La,Sr)GaO4 (Eg = 3.8 eV), both of which contain the K2NiF4 symmetry. The dimensional confinement of our 1D superlattices has been confirmed by x-ray diffraction and Z-contrast STEM. Linearly polarized optical spectroscopy shows clear anisotropic characteristics and one-dimensional electronic confinement of the spin-orbit split Jeff = 1/2 band, notable in studies on Sr2IrO4. Spin and orbital excitations observed in resonant inelastic x-ray scattering spectra suggest larger exchange interactions and more deconfined orbital excitations in the 1D IrO2 stripes as compared to its Sr2IrO4 counterpart. The observed electronic confinement and localized spin-structure are quite consistent with density functional theory calculations. The method of transforming layered materials into 1D striped structures is a viable technique for obtaining dimensional-crossover phase transitions while tuning from two- to one-dimension.
3:30 PM - *ES10.12.04
Metal-Insulator Transitions in All-In/All-Out Ordered 5d Pyrochlore Oxides
Tae Won Noh 1 2 , Woo Jin Kim 1 2 , C. H. Sohn 1 2 , Nguyen Thi Minh Hien 1 2 , John Gruenewald 1 3 , Oleksandr Korneta 1 2 , Soon Jae Moon 4 , S. S. Ambrose Seo 3
1 Center for Correlated Electron Systems-Institute for Basic Science (IBS), Department of Physics and Astronomy, Seoul National University, Seoul Korea (the Republic of), 2 Department of Physics and Astronomy, Seoul National University, Seoul Korea (the Republic of), 3 Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky, United States, 4 Department of Physics, Hanyang University, Seoul Korea (the Republic of)
Show AbstractThere are much attentions to the 5d transition metal oxides with pyrochlore structure. Spins in the pyrochlore lattice usually have the geometric frustration. However, many 5d pyrochlore oxides show all-in-all-out (AIAO) magnetic ordering, possibly due to the large spin orbit coupling. Also metal-insulator transitions (MIT) have been reported to occur concurrently at the AIAO ordering temperature TN, suggesting the Slater-type MIT mechanism. Recently, we showed the band-gap edge of 5d pyrochlore Cd2Os2O7 starts to change at TN. However, the free carrier density remains to exist at lower T, suggesting the Lifshitz-type MIT. As a natural consequence of such MIT, an AIAO metallic phase could exist. [1]
Pyrochlore iridates R2Ir2O7 (with R = rare earth elements) are other interesting 5d pyrochlore oxides. Similarly to Cd2Os2O7, many earlier works reported that they experience both MIT and AIAO magnetic orderings concurrently. With such a novel ground state, the AIAO ordering will host topologically non-trivial phases. Consequently, R2Ir2O7 have been predicted to exhibit a variety of exotic physical phenomena, such as the Weyl semimetallic state and topologically insulating behavior [2].
Here, we will compare MIT and AIAO ordering of R2Ir2O7 epitaxial films with those of Cd2Os2O7. We grew epitaxial Sm2Ir2O7 and Nd2Ir2O7 films on YSZ substrates. We found that MIT of these iridates films occur below their respective TN, similarly to the Cd2Os2O7 case. Using the epitaxial films, we measured magnetoresistance (MR) up to 30 T. We observed a couple of intriguing phenomena. First, R2Ir2O7 epitaxial films show negative MR behavior below ~ 20 K and positive MR above. The crossover temperatures are close to the AIAO ordering temperatures of the rare earth ions. So we attribute that the negative MR should come from the f - d exchange coupling between the electrons at the Ir sites and localized moments at the R sites. Second, we observed unconventional domain wall (DW) conductance in the R2Ir2O7 epitaxial films. It has been reported that the topological phases with AIAO-type should have metallic DW conductance [3]. We observed metallic DW the conductance in Nd2Ir2O7 film, while Sm2Ir2O7 film showed an insulating behavior. This metal-insulator DW conductance change is consistent with a recent theoretical prediction [4].
Reference
[1] C. H. Sohn et al., Phys. Rev. Lett. 115, 226402 (2015).
[2] W. Witczak-Krempa et al., Annu. Rev. Condens. Matter Phys. (2014).
[3] E. Y. Ma et al., Science 350, 6260 (2015).
[4] B. J. Yang et al., Phys. Rev. Lett. 112, 246402 (2014).
ES10.13: Correlated Oxides—Interfaces and Magnetism IV
Session Chairs
Elke Arenholz
Tae Won Noh
Thursday PM, April 20, 2017
PCC North, 200 Level, Room 222 A
4:30 PM - ES10.13.01
Heteroepitaxy of Fe3O4/Muscovite—A New Perspective for Flexible Spintronics
Ping-Chun Wu 1 , Ping-Fan Chen 2 , Thi Hien Do 2 , Ying-Hui Hsieh 1 , Chun-Hao Ma 3 , Thai Duy Ha 4 , Kun-Hong Wu 5 , Yi-Chun Chen 5 , Jenh-Yih Juang 4 , Lukas Eng 6 , Chun-Fu Chang 7 , Po-Wen Chiu 3 , Liu Hao Tjeng 7 , Ying-Hao Chu 1
1 Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu Taiwan, 2 , Academia Sinica, Taipei Taiwan, 3 , National Tsing Hua University, Hsinchu Taiwan, 4 , National Chiao Tung University, Hsinchu Taiwan, 5 , National Cheng Kung University, Tainan Taiwan, 6 , Dresden University of Technology, Dresden Germany, 7 , Max Planck Institute for Chemical Physics of Solids, Dresden Germany
Show AbstractSpintronics has captured a significant attention since it was proposed. It has been triggering numerous research groups to pay their efforts on pursuing spin-related electronic devices. Recently, flexible and wearable devices are on high demand due to their outstanding potential in practical applications. In order to bring spintronics into the realm of flexible devices, we demonstrate that it is feasible to grow epitaxial Fe3O4 film, a promising candidate for realizing spintronic devices based on the tunneling magnetoresistance, on flexible muscovite. In this study, the heteroepitaxy of Fe3O4/muscovite is characterized by x-ray diffraction, high-resolution transmission electron microscopy, and Raman spectroscopy. The chemical composition and magnetic feature are investigated by a combination of x-ray photoelectron spectroscopy and x-ray magnetic circular dichroism. The electrical and magnetic properties are examined to acknowledge the preservation of the primitive properties of Fe3O4. Furthermore, to demonstrate that the Fe3O4/muscovite heterostructure is suitable for flexible devices, various bending tests were performed. With help of tests, we deliver the tunability of functionalities and confirm that the heterostructures retain the physical properties under repeated cycles. These results illustrate that the Fe3O4/muscovite heterostructure can be a potential candidate for applications in flexible spintronics.
4:45 PM - *ES10.13.02
Ultrastrong Magnetic Coupling at the La0.7Sr0.3MnO3-SrRuO3 Interface
Kathrin Dorr 1
1 , MLU Halle-Wittenberg, Halle Germany
Show Abstract
The La0.7Sr0.3MnO3-SrRuO3 (LSMO-SRO) interface between two conducting ferromagnetic oxides has long been known for antiferromagnetic (afm) interface coupling reflected in the observation of an exchange-bias effect. Superlattices showed an immense strength of afm coupling which could only be overcome in magnetic fields beyond 4 T at 10 K. We show that the two terminations of this interface can be grown by pulsed laser deposition in bilayers of reversed layer sequence. Interdiffusion is low enough to achieve well-defined MnO2-SrO (1) and RuO2-La0.7Sr0.3O (2) interfaces. X-ray magnetic circular dichroism measurements used to track the elemental magnetic hysteresis curves of Ru and Mn reveal fundamentally different switching mechanisms for the two LSMO-SRO interfaces. While interface (2) has characteristics of an exchange bias system, interface (1) shows a Mn-Ru coupling strength exceeding that in the interior of the SRO layer. As a consequence, an interface layer of SRO can be switched as a unit with the LSMO layer in small magnetic field, inducing a controllable non-collinear spin texture into SRO. Density functional theory confirms the ultrastrong afm coupling for the termination (1) of the LSMO-SRO interface. Our results demonstrate that low-diffusion oxide interfaces can reach ultrastrong magnetic exchange that breaks the collinear spin order in the interior of a ferromagnetic layer and, thus, can be utilized to control the spin texture of that layer.
5:15 PM - *ES10.13.04
Controlled Lateral Anisotropy in Correlated Manganite Heterostructures by Interface-Engineered Oxygen Octahedral Coupling
Mark Huijben 1 , Zhaoliang Liao 1 , Gertjan Koster 1 , Guus Rijnders 1
1 , University of Twente, Enschede Netherlands
Show AbstractControlled in-plane rotation of the magnetic easy axis in manganite heterostructures by tailoring the interface oxygen network could allow the development of correlated oxide-based magnetic tunneling junctions with non-collinear magnetization, with possible practical applications as miniaturized high-switching-speed magnetic random access memory (MRAM) devices. Here, we demonstrate how to manipulate magnetic and electronic anisotropic properties in manganite heterostructures by engineering the oxygen network on the unit-cell level [1]. The strong oxygen octahedral coupling is found to transfer the octahedral rotation, present in the NdGaO3 (NGO) substrate, to the La2/3Sr1/3MnO3 (LSMO) film in the interface region. This causes an unexpected realignment of the magnetic easy axis along the short axis of the LSMO unit cell as well as the presence of a giant anisotropic transport in these ultrathin LSMO films. Furthermore, we present direct evidence for the relaxation of oxygen 2p and Mn 3d orbital (p-d) hybridization coupled to the layer dependent octahedral tilts within a LSMO film driven by interfacial octahedral coupling. An enhanced Curie temperature is achieved by reducing the octahedral tilting via interface structure engineering. Atomically resolved lattice, electronic and magnetic structures together with X-ray absorption spectroscopy demonstrate the central role of thickness dependent p-d hybridization in the widely observed dimensionality effects present in correlated oxide heterostructures.
[1] Z. Liao et al., Nature Mater. 15, 425 (2016).
ES10.14: Poster Session III
Session Chairs
Satoshi Okamoto
Morgan Trassin
Friday AM, April 21, 2017
Sheraton, Third Level, Phoenix Ballroom
9:00 PM - ES10.14.01
Angle-Resolved Photoemission Spectroscopy on Strained NdNiO3 Thin Films
Daniele Preziosi 1 , Julien Rault 2 , Mathieu Grisolia 1 , Julien Varignon 1 , Agnes Barthelemy 1 , Francois Bertran 2 , Patrick Le Fevre 2 , Manuel Bibes 1
1 , UMR137-CNRS/Thales, Palaiseau France, 2 , Synchrotron SOLEIL, Gif-sur-Yvette France
Show AbstractThin films of perovskite rare-earth nickelates (ReNiO3, Re=rare-earth elements) represent an interesting playground for fundamental physics [1] and also have attractive perspectives in oxide electronics [2] and spintronics [3]. Nickelates exhibit a first-order metal-to-insulator transition (MIT) whose onset is linked to an anti-ferromagnetic (AFM) order characterized by a wavevector k = (¼, ¼, ¼) in the pseudocubic setting. The spin configuration can be described as a stacking ‘up-up-down-down-up-up-down-down’ of ferromagnetically ordered planes perpendicular to the pseudo-cubic [111]pc direction [4]. The divergence of the static spin-susceptibility at T=TNéel is usually associated with nesting, namely, the Fermi surface (FS) (with a mixed Ni 3d-O 2p character) contains connected regions in the Brillouin zone (BZ) which can perfectly overlap, in a given direction, through the nesting wave vector [5]. This enhanced responsiveness of the nickelates’ FS may result in novel electronic/magnetic phases such as charge/spin density waves, orbital reconstruction and percolation. We will report the electronic structure variation of NdNiO3 thin films (used as a model nickelate material) in terms of thickness (wedge samples) and epitaxial strain (growth on different substrates), through in-situ synchrotron-based angle-resolved photoemission spectroscopy (ARPES) technique with the aim to verify if the MIT could be linked to some changes of the observed FS’s maps.
[1] Medarde, M.L., J. Phys.: Condens. Matter., 9, 1679-1707 (1997).
[2] Scherwitzl, R., et al., Adv. Mater. 22, 5517-5520 (2010).
[3] Grisolia, M .N., et al., Nature Physics 12, 484-492 (2016).
[4] Garcia-Munoz,J.L., et al., Phys. Rev. B 50, 978 (1994).
[5] Lee, S., et al., Phys. Rev. Lett. 106, 016405 (2011).
This work was supported by the ‘MINT’ ERC Consolidator Grant #615759.
9:00 PM - ES10.14.02
Size Driven Polarization Rotation as well as Magnetic Order Tuning in a Magnetoelectric Multiferroic
Narayan Bastola 1 , Rajeev Ranjan 1
1 , Indian Institute of Science, Bangalore India
Show AbstractIn general, crystallite size reduction is known to destroy magnetic ordering as well as polarization (ferroic order) in the ferroelectric and magnetic systems. We show that the magnetoelectric multiferroic BiFeO3-PbTiO3 exhibits polarization switching from [001] (tetragonal P4mm) to [111] (rhombohedral R3c) direction on reducing the crystallite size below 0.5 microns. This result provides the experimental proof of a similar mechanism predicted theoretically for a nanowire of tetragonal PbTiO3 with its non-polar [111] direction parallel to the wire axis. It is argued that the main driving force for this transformation is the depolarization field. The transformation virtue reduced size is not only Interferroelectric but also the magnetic ordering. The paramagnetic (P4mm) to antiferromagnetic (R3c) transformation can be made to undergo on physical reduction of the crystallite size from ~10 microns to 0.5 microns. This unusual transformation is made possible by virtue of strong coupling between the structural and magnetic degrees of freedom and size induced interferroelectric instability. The system possesses a giant tetragonality (c/a – 1 =0.18) and hence the large depolarizing field, which is the main driving force for a size induced magneto-ferroelectric transformation. The transformation occurs by virtue of two interlinked phenomenon: (i) size driven inter-ferroelectric transformation and (ii) locking of one of the ferroelectric phase with magnetic order. The driving force for this unusual transformation is argued to be the long range forces - depolarizing field and the stress associated with the high energy ferroelectric-ferroelastic domain walls.
9:00 PM - ES10.14.03
Manipulation of Magnetic Properties of LaMnO3 through Interface Engineering
Liang Wu 1 , Changjian Li 2 , Xiao Wang 3 , Jing Ma 1 , Ce-Wen Nan 1 , Yujun Zhang 1
1 , Tsinghua University, Beijing China, 2 , National University of Singapore, Singapore Singapore, 3 , Nanyang Technological University, Singapore Singapore
Show AbstractNovel physical properties in oxide heterostructures which don’t arise in the bulk materials may emerge when the constituents meet face to face. Atomically sharp transition to a ferromagnetic phase between 5 and 6 unit cell when polar antiferromagnetic LaMnO3 (LMO) (001) films are grown on SrTiO3 (STO) substrates has been reported by X. Renshaw Wang, et. al. As a comparison, the ferromagnetism of LMO grown on LaAlO3 (LAO) was suppressed, as a result, the LMO remained to be antiferromagnetic, which was explained to the interplay of compressive stain and the polar continuity. Here we further clarify the effect of the two possible factors, by preparing the comparative LMO/ STO/ LAO (001) samples, where the same strain condition has been maintained as LMO/ LAO and the polar discontinuity at the interface of LMO/ STO has been recalled. The results suggest that the polar discontinuity plays a dominant role in the ferromagnetic transition of LMO and which provides a deeper understanding of the polar discontinuity interface. Further, we investigated the interaction between two polar materials by preparing of LMO/ LAO and LAO/ LMO on STO (001) substrates, the enhancement of ferromagnetism of LMO layer in above samples indicates that the polar effect is superposed and which offers a crucial novel method to manipulate artificial functionalities through interface engineering.
9:00 PM - ES10.14.04
Multifunctional Properties of Highly c-Axis Oriented NZFO Thin Films
Dhiren Pradhan 1 , Shalini Kumari 1 , Aswini Pradhan 2 , Ram Katiyar 1
1 , University of Puerto Rico, San Juan, Puerto Rico, United States, 2 , Norfolk State University, Norfolk, Virginia, United States
Show AbstractAs fabrication technology pushes the magnetic structures into the nanoscale dimensions, understanding the magnetization processes of these structures is of fundamental interest, and key to future applications in spin-caloritronics, hard disk drives, high density non-volatile magnetoresistive random memory (MRAM), spintronic and other multifunctional devices.. Ultimately, the desired functionality of an all-oxide device would likely require that one can incorporate high-temperature magnetic spinel ferrites with perovskites that display a range of functionalities, e.g., dielectric, piezoelectric, ferroelectric, metallic, magnetic, etc. Ferrimagnetic materials are the important class of magnetic materials which exhibit remarkable magnetic properties, high resistivity, low eddy current and high Neel temperature (TN) along with spin dependent band gaps. In continuation to our search for a suitable magnetic material for multifunctional applications, we have studied the dielectric, optical and magnetic properties of NZFO thin films. Of the ferrites family, NZFO expresses high degree of magnetostriction (106 λs = -24), thus making it an attractive ferrimagnetic candidate for composite multiferroics. The optimized ratio Ni0.65Zn0.35Fe2O4 has been chosen for the present study since this composition exhibits highest saturation magnetization in the entire Nickel-Zinc ferrite series, with a high magnetic Curie temperature (~ 600 K). The observation of only (004) reflection in the XRD patterns confirm the c-axis oriented and high quality growth of NZFO thin films. The presence of mixed valences of Fe+2/Fe+3 cations is probed by X-ray photon spectroscopy (XPS), which support the catonic ordering-mediated large dielectric response. Our investigations reveal Ni0.65Zn0.35Fe2O4 to be an indirect band gap material (1.8 eV ) with a direct gap at 2.55 eV and the reasons of coexistence of both band gap have been establishesd . These nanostructures exhibit high saturatution magnetization, low coercive field with a ferrimagnetic-paramagnetic phase transition of ~713 K. Magnetic force microscopy studies revealed the stripe like domain structure of the investigated thin films. NZFO thin films exhibits low loss tangent, high dielectric permittivity an large magnetization with soft magnetic behavior above room temperature elucidate the possible potential candidates for multifunctional and spintronics nanoscale device applications.
9:00 PM - ES10.14.05
Magnetic and Magnetoresistive Behavior of MnFe2O4 Nanofibers Obtained by Electrospinning
Lizeth Vazquez Zubiate 1 , Diana Carrillo 1
1 Ciencias basicas, Universidad Autonoma de Ciudad Juarez, Juarez, Mexico Mexico
Show AbstractThe synthesis of the MnFe2O4 nanofibers was carried out by the electro-spinning technique in order to study the effect of microestructure on the magnetic and magnetoresistive properties when measured at low temperatures. In this work, the precursor solution was compose of 15, 19 and 20 %Wt of PVP, with molecular weight Mw 1, 300 K, Mn(NO3)2H2O and Fe(NO3)39H2O in a mixture of water and alcohol. The solution was vigorously stirred for 1 h and then, it was flowing out through the needle at a constant flow rate of 0.3 ml/h. After collecting the fibers, these were annealed at 1100°C by 1 h in nitrogen atmosphere. The characterization was carried out by X-ray diffraction (DRX), Scanning Electron Microscopy (SEM) and Vibrating Sample Magnetometry (VSM). MnFe2O4 pure phase was found in the nanofibers from XRD patterns. Magnetic properties of calcined samples characterized by VSM were measured at low temperature to determine the magnetic interactions behavior of the fibers. A change was found in the magnetic interactions as temperature goes down because the magnetocrystalline anisotropy dependence on it by means of hysteresis loops shape. In addition, the magnetoresistance properties were measured by VSM with two-point method.
9:00 PM - ES10.14.06
Synthesis and Characterization of Novel Inverted NiO@NixMn1-xO Core-Shell Nanoparticles
Samiul Hasan 1 , R.A. Mayanovic 1 , Mourad Benamara 2
1 Department of Physics, Astronomy and Materials Science, Missouri State University, Springfield, Missouri, United States, 2 Institute for NanoScience & Engineering, University of Arkansas, Fayetteville, Arkansas, United States
Show AbstractMagnetic core-shell nanoparticles have the potential for numerous applications, such as in magnetic recording media, magnetic resonance imaging, drug delivery or hyperthermia, and spin valves. Inverse core-shell nanoparticles, comprised of an antiferromagnetic (AFM) core covered by a ferromagnetic (FM) or ferrimagnetic (FiM) shell, are of current interest due to the tunability of their magnetic properties. NiO is typically antiferromagnetic in nature and has a Néel temperature of 523 K. Our primary objective in this project is to synthesize and characterize inverted core-shell nanoparticles (CSNs) comprised of a NiO (AFM) core and a shell consisting of a NixMn1-xO (FM/FiM) compound. The synthesis of the CSNs was made using a two-step process. The NiO nanoparticles were synthesized using a chemical reaction method. Subsequently, the NiO nanoparticles were used to grow the NiO@NixMn1-xO CSNs using our hydrothermal nano-phase epitaxy method. XRD structural characterization shows that the NiO@NixMn1-xO CSNs have the rock salt cubic crystal structure throughout. SEM-EDS data indicates the presence of Mn in the CSNs. SQUID magnetic measurements show that the CSNs exhibit AFM/FM or AFM/FiM characteristics with a coercivity field of 425 Oe at 5 K. The field cooled vs zero field cooled hysteresis loop measurements show a significant exchange bias effect between the AFM NiO core and FM/FiM NixMn1-xO shell of the CSNs. The results of additional TEM and magnetic characterization are discussed.
9:00 PM - ES10.14.07
Enhanced Dielectric and Ferroelectric Properties of 0.7BF-0.3PT Thin Films Derived by an Ethylene Glycol Modified Sol-Gel Method
Guoping Lu 1 , Hanting Dong 1 , Jianguo Chen 1 , Jinrong Cheng 1
1 School of Materials Science and Engineering, Shanghai University, Shanghai China
Show Abstract0.7BiFeO3-0.3PbTiO3 (BF-PT) thin films on stainless steel (SS) substrates were fabricated by an ethylene glycol (EG) modified sol-gel method. Perovskite structure of BF-PT thin films was examined by the X-ray diffraction analysis. With the increase of EG, BF-PT thin films with enhanced dielectric and ferroelectric properties were got. Crack-free BF-PT thin films with thickness of 1.2 μm were prepared for EG volume content of 33%, and the dielectric permittivity was 273 at the frequency of 1k Hz showing better dielectric properties compared with BF-PT thin film without EG modified. The remnant polarization (Pr) of 33% volume content EG modified BF-PT thin film was nearly twice reaching 18.1 μC/cm2, and lower leakage current density was obtained with 4.45×10-5 A/cm2 under the field of 200 kV/cm. Such enhanced performance indicated that the PZT thin films prepared on SS substrates by the EG modified sol-gel process exhibited their potentiality in applications.
9:00 PM - ES10.14.08
Enhanced Dielectric and Piezoelectric Properties of the BiFeO3-PbTiO3-BaZrO3 Ternary High Curie Temperature Ceramics
Jie Jian 1 , Jianguo Chen 1 , J.R. Cheng 1
1 School of Materials Science and Engineering, Shanghai University, Shanghai China
Show AbstractBiFeO3-PbTiO3-based solid solutions have been investigated for the development of piezoelectric ceramics with high Curie temperatures. It is observed that with the mix of the third component BaZrO3, the dielectric loss is decreased and piezoelectric property is highly improved compare with the BiFeO3-PbTiO3 (BF-PT) binary system. In this paper, BiFeO3-PbTiO3-BaZrO3 (BF-PT-BZ) solid solutions with composition of xBF-(0.95-x)PT-0.05BZ (x = 0.60, 0.62, 0.63, 0.64, 0.66) were synthesized via solid-state reaction method. Samples calcined at 1020 oC exhibit high density and pure phase. The grain size of xBF-(0.95-x)PT-0.05BZ is in the range from 10 μm to 22 μm, showing obvious variation. Values of dielectric constant er of xBF-(0.95-x)PT-0.05BZ increased to 265 and then decreased while the loss tand is on the contrary when the BiFeO3 (BF) content varies from 0.60 to 0.66 at low frequency. The Tc is from 550 oC to 560 oC with the increasing content of BF. xBF-(0.95-x)PT-0.05BZ ceramics for x=0.63 is around the morphotropic phase boundary(MPB), exhibiting most saturated polarization , with remnant polarization Pr of 43.2 μC/cm2 and coercive field Ec of 61.6 kV/cm. The values of d33, kp and Qm of 0.63BF-0.32PT-0.05BZ are 118 pC/N, 0.322 and 501 respectively, showing tremendous potential for high Curie temperature piezoelectric applications.
Symposium Organizers
John Heron, University of Michigan
Satoshi Okamoto, Oak Ridge National Laboratory
Morgan Trassin, ETH Zürich
Pu Yu, Tsinghua University
Symposium Support
CrysTec Gmbh
Lake Shore Cryotronics Inc
NT-MDT America Inc.
Radiant Technologies, Inc
Twente Solid State Technology B.V.
ES10.15: Composite Multiferroics—Electric Field Control of Magnetism and Magnetoelectric Interfaces II
Session Chairs
Friday AM, April 21, 2017
PCC North, 200 Level, Room 222 A
9:15 AM - *ES10.15.01
Electric-Field Control of Magnetism in Strain-Coupled Multiferric Heterostructures
Sebastiaan van Dijken 1
1 , Aalto University, Espoo Finland
Show AbstractSpintronic devices currently rely on magnetic switching or controlled motion of magnetic domain walls by an external magnetic field or electric current. Achieving the same degree of magnetic controllability using an electric field has potential advantages including low power consumption. Here, an approach to electrically control local magnetic properties will be discussed [1-4]. The method is based on recurrent strain transfer from regular ferroelastic stripe domains in a ferroelectric BaTiO3 substrate to magnetostrictive films (e.g. CoFe, CoFeB, and Fe). Dominance of the strain-induced magnetoelastic anisotropy in these heterostructures causes full imprinting of ferroelectric domain patterns into ferromagnetic films and strong pinning of magnetic domain walls onto ferroelectric boundaries [1,2]. Optical polarization microscopy measurements of the ferromagnetic and ferroelectric domain structures indicate that domain correlations and strong inter-ferroic domain wall pinning are maintained in an applied electric field. As a result, deterministic electric-field control over the formation and erasure of ferromagnetic domains [3,4] and reversible motion of magnetic domain walls [5] are obtained. In addition, regular modulations of magnetic anisotropy in strain-coupled multiferroic heterostructures provide a versatile platform for the excitation and manipulation of spin waves [6]. These findings open up new routes towards electric-field driven spintronics and magnonics.
[1] T.H.E. Lahtinen et al., Adv. Mater. 23, 3187 (2011)
[2] K. J. A. Franke et al., Phys. Rev. B 85, 094423 (2012)
[3] T.H.E. Lahtinen et al., Sci. Rep. 2, 258 (2012)
[4] Y. Shirahata et al., NPG Asia Mater. 7, e198 (2015)
[5] K. J. A. Franke et al., Phys. Rev. X 5, 011010 (2015)
[6] B. Van de Wiele et al., Sci. Rep. 6, 21330 (2016)
9:45 AM - *ES10.15.03
Real Space Studies of the Electronic and Magnetic Properties of Oxide Multiferroic Interfaces by Aberration Corrected STEM-EELS
Javier Grandal 1 , Juan I. Beltran 1 , G. Sanchez-Santolino 2 , Javier Tornos 3 , M. Cabero 1 , F. Javier Rodriguez 1 , Carlos Leon 1 4 , M. Munoz 3 , J. Santamaria 1 4 , Maria Varela 1 4
1 Fisica de Materiales, Universidad Complutense, Madrid Spain, 2 Institute of Engineering Innovation, School of Engineering, University of Tokyo, Tokyo Japan, 3 , Instituto de Ciencia de Materiales de Madrid - CSIC, Madrid Spain, 4 , Instituto de Magnetismo Aplicado UCM-ADIF-CSIC, Las Rozas de Madrid Spain
Show Abstract
Novel functionalities may arise in heterostructures combining complex oxide materials exhibiting different ferroic orders. In this talk we will discuss the electronic and magnetic properties of oxide based ferromagnetic (FM) /ferroelectric (FE) interfaces where FE BaTiO3 (BTO) barriers are sandwiched between FM La0.7Sr0.3MnO3 (LSMO) layers. We will combine the use of advanced electron microscopy techniques such as electron energy-loss spectroscopy (EELS) in the aberration-corrected scanning transmission electron microscope (STEM) with density-functional calculations to study the interplay between local electronic phenomena and multiferroic behavior. Real space measurements of local polarization obtained from the analysis of atomic resolution images will be compared to magnetic quantities inferred from high spatial resolution energy-loss magnetic chiral dichroism (EMCD), a technique directly sensitive to the local magnetic moment. Both local magnetization and polarization measurements will be discussed in the light of electronic properties projected to atomic and orbital entities such as interface charge transfer and orbital anisotropies. Acknowledgements: Research at UCM sponsored by Fundación BBVA and Spanish MINECO MAT2015-66888-C3-3-R and MAT2015-66888-C3-1-R and by the ERC Proof of Concept Grant MAGTOOLS.
10:15 AM - ES10.15.04
Abnormal Negative Electroresistance and Giant Resistance Modulation in Self-Strained Manganite/Piezoelectric Heterostructures
Zhenping Wu 1 2 , Stefano Gariglio 2 , Margherita Boselli 2 , Alexandre Fete 2 , Marta Gibert 2 , Li Danfeng 2 , Michel Viret 3
1 , Beijing University of Posts and Telecommunications, Beijing China, 2 , University of Geneva, Geneva Switzerland, 3 , CNRS, Paris France
Show AbstractIn perovskite manganite based system, the cross coupling between different degrees of freedom (structural, charge, spin, and orbital) give rise to rich physical phenomena, such as colossal magnetoresistance, charge/orbital ordering, and electronic phase separation (EPS). One of the hallmarks in these materials is the extreme sensitive to external perturbations, such as magnetic field, electric field, light, etc. In this work, an unusual current-induced resistance increase is observed in the micro-bridge patterned La0.8Ca0.2MnO3 (LCMO)/PMN-PT heterostructure, by considering the electric field distribution, we hypothetically suggest a lattice distortion in self-strained manganite film to cause the abnormal ER effect. Moreover, the observed ER effect as well as the memory effect could be manipulated by a reversible biaxial strain induced by PMN-PT substrate, even +4 kV/cm E-field can cause a ~ 98% ΔR/R0 resistance change. We also show that the large current will lead to a decrease of RS due to the melt of insulating phase. The formed metallic filament could also be collapsed by further increased current, results in a higher RS phase, showing a resistive switching phenomena. These findings indicate that the emergent EPS formation can be selectively manipulated by both current and strain, which provides a new platform for developing new device engineering and a fuller understanding of the balanced energetics that drive
emergent behaviors in complex materials.
ES10.16: Complex Oxides—Interfaces and Magnetism
Session Chairs
Friday PM, April 21, 2017
PCC North, 200 Level, Room 222 A
11:00 AM - ES10.16.01
Spin Reconstruction as a Function of Thickness at the (111)-Oriented La0.7Sr0.3MnO3/LaFeO3 Interface
Ingrid Hallsteinsen 1 2 , Magnus Moreau 1 , Magnus Nord 3 , Emil Christiansen 3 , Alexander Grutter 4 , Dustin Gilbert 4 , Brian Kirby 4 , Randi Holmestad 1 , Elke Arenholz 2 , Thomas Tybell 1
1 Department of Electronics and Telecommunication, Norwegian University of Science and Technology (NTNU), Trondheim Norway, 2 Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 3 Department of Physics, Norwegian University of Science and Technology (NTNU), Trondheim Norway, 4 Center of Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland, United States
Show AbstractTransition metal oxides exhibit strong coupling between structure and magnetic properties, enabling to engineer magnetic heterostructures with well-defined magnetic properties. Of special interest is the magnetic response between ferromagnetic/antiferromagnetic interfaces. We present a combined study of the correlation between structural and magnetic domains; using x-ray absorption spectroscopy with photoemission electron microscopy, spin polarized neutron reflectometry and scanning transmission electron microscopy. As model system we use epitaxial heterostructures of antiferromagnetic LaFeO3(LFO) and ferromagnetic La0.7Sr0.3MnO3 (LSMO) grown in the (111)-orientation to maximize magnetic and structural coupling between the two, varying the thickness of the antiferromagnetic layer. When the LFO layer in the heterostructures is thicker than 4nm, a purely antiferromagnetic response with in-plane antiferromagnetic axis is found and small magnetic and structural domains of ~100nm in size. However when the LFO layer is thinner than 4nm an induced ferromagnetic moment, ~1.6-2.0 µB/Fe –atom, at the Fe atoms is found antiparallel to the ferromagnetic moments of LSMO. This effect reaches 2-4 monolayers into LFO from the LSMO interface, while the rest of the film is antiferromagnetic with an out-of-plane antiferromagnetic axis. The thicker LFO relax into many, small structural domains, while in the thin LFO layers larger structural domains are found, ~500nm in size, where the oxygen octahedral rotation at the LSMO/LFO interface is reduced. The data will be discussed in a framework where the different structural domain for thin and thick LFO epilayers modifies the preferred antiferromagnetic axis and imply that thicker LFO relax by structural domains, while thinner LFO relax by spin reorientation.
11:15 AM - *ES10.16.02
Novel Properties of 5d Transition Metal Compounds
Xiangang Wan 1
1 , Nanjing University, Nanjing China
Show AbstractIn 5d transition metal compounds, novel property arise from the interplay of electron correlations and spin-orbit interactions. We focus on describing the topological Weyl-Semimetal in pyrochlore iridates, the Axion insulatior in spinel osmates, the Slater insulator in perovskite osmates. We also discuss the anisotropic unscreened Coulomb interaction in ferroelectric metal LiOsO3, and the novel properties in WTe2.
11:45 AM - *ES10.16.03
Interface Driven Emergent Phases in Iridates
Masashi Kawasaki 1 2 , Masaki Uchida 1 2
1 , The University of Tokyo, Tokyo Japan, 2 , RIKEN CEMS, Wako Japan
Show AbstractStrong spin-orbit interaction in iridates has attracted considerable attention. Epitaxial heterostructures are now constructed to examine their properties, especially the effect of the interface. We introduce two examples in this talk. Pyrochlore iridate heterostuructures with all-in-all-out spin configurations enable us to create and annihilate magnetic domain boundary at the interface in a controlled manner, clarifying its metallic conduction. Perovskite heterostructures of SrRuO3/SrIrO3 is shown to host magnetic skyrmions due to Dzyaloshinskii-Moriya interaction at the interface. We extend possible functionalization and device application of this class of materials and properties.
ES10.17: Complex Oxides—Structure and Phase Properties
Session Chairs
Satoshi Okamoto
Morgan Trassin
Friday PM, April 21, 2017
PCC North, 200 Level, Room 222 A
12:15 PM - ES10.17.01
Pressure-Induced Changes of Chemical Composition and Electronic Properties of Ultra-Thin Manganites
Rama Vasudevan 1 , Anton Ievlev 1 , Olga Ovchinnikova 1 , Arthur Baddorf 1 , Sergei Kalinin 1 , Petro Maksymovych 1
1 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractThe use of scanning probe microscopy (SPM) to explore, map and locally modify properties of thin films of complex oxides and nanostructures is routine. However, in many studies the prevailing assumption is that the application of bias to the SPM tip in contact with the sample, or pressure exerted by the scanning of the tip, does not affect the chemistry of surface layers, and instead, observed modifications are due to physical effects (such as switching of electric dipoles). Here, we show that this assumption is highly questionable. By scanning the surface of ultra-thin films of LaMnO3, we detect changes in the conductivity, as well as in the surface potential in ultra-high vacuum conditions. Furthermore, by site-correlated time-of-flight secondary ion mass spectrometry, we show that application of pressure by the tip (~300MPa) is sufficient to change the local cation stoichiometry two layers beneath the surface. Application of electrical bias can reverse some of these effects. These studies show the potential to tune the properties of oxides through local chemical control, and suggest that chemical effects may be much more prevalent than commonly admitted. This research was sponsored by the Division of Materials Sciences and Engineering, BES, US DOE (RKV, PM, SVK). This research was conducted at the Center for Nanophase Materials Sciences, which also provided support (AI, APB, OO) and is a DOE Office of Science User Facility.
12:30 PM - ES10.17.02
Structural and Electronic Properties of SrTiO3/GaAs Hetero-Interfaces
Liang Hong 1 , Serdar Ogut 1 , Robert Klie 1
1 , University of Illinois at Chicago, Chicago, Illinois, United States
Show AbstractThe SrTiO3/GaAs heterojuction can offer superior electronic and optical properties which can be potentially used in creating new devices for magneto-optical or electro-optical applications. These devices can only be realized if SrTiO3 is epitaxially deposited on GaAs, producing interfaces with low interface state densities. Therefore, an understanding of the growth and interface properties is critical for the integration and fabrication of reliable heterojunctions. The SrTiO3/GaAs interfaces were characterized previously using atomic-resolution scanning transmission electron microscopic (STEM) imaging and electron energy-loss spectroscopy (EELS). It has been observed that SrO-terminated SrTiO3 films are epitaxially grown on As-terminated GaAs with atomically sharp interfaces. However, the first-principles density functional theory (DFT) calculations predicted a SrO/Ga interface as the lowest-energy structure. For the purpose of clarifying this discrepancy, in this work, GaAs films are grown on SrO-terminated SrTiO3 instead of using GaAs as substrate, STEM-EELS combined with DFT calculations are used to determine the energetically favorable termination of GaAs. The atomically sharp SrO/As interface is observed in the STEM images and the interfacial SrO layer is found to be oxygen highly deficient by Ti L-edge EEL spectrum. DFT structural models of various interfacial configurations in (2x2) supercells are constructed and fully relaxed. Formation energy phase diagram of these models illustrates two most stable interfaces which are Sr/As and SrO/Ga. The structural and electronic features of these interfaces as well as the effect of interfacial oxygen vacancies are discussed.
Acknowledgment: This work was supported by the National Science Foundation (Grant No. DMR-1408427). This work made use of instruments in the Electron Microscopy Service and the High Performance Computing Clusters at University of Illinois at Chicago.