Ferroics, Multiferroics and Magnetoelectrics: Reconsidering New Paths to Large Transduction, Ultra-Low Power Sensors and Giant Energy Conversion

The ability to tune both magnetic and electric properties concomitantly in magnetoelectric (ME) composite heterostructures, consisting of magnetostrictive and piezoelectric phases coupled through strain with orders-of-magnitude larger ME coupling coefficient than single-phase multiferroics due to additional functionalities and makes them very promising in many applications and devices [1,2]. This has generated a revived interest in multiferroics, and is projected to play a critical role in next-generation applications ranging from transducers, tunable inductors, gyrators, magnetic sensors to high-frequency filters and communication devices. In this talk we highlight different approaches to achieve maximum ME coupling in heterostructures of magnetostrictive films deposited on domain-engineered relaxor ferroelectric single crystals. Much work has been done over the past decade to maximize the magnetoelectric (ME) coupling coefficient, α_ME, the figure of merit for these composites that can be enhanced through deliberate choice of materials as well as carefully controlling the interface. For the piezoelectric phase, relaxor ferroelectrics have attracted much attention recently due to a piezoelectric coefficient an order of magnitude larger than conventional lead zirconate-titanate [3] especially in proximity to morphotropic phase boundary. In the ME heterstructures we demonstrated that by exploiting the large ferroelectric phase transitional strain in piezoelectric substrate, the converse magnetoelectric coupling coefficient is expected to be greatly up to 4x enhanced as compared to linear piezoelectricity [4,5]. In this presentation, the impact of this enhancement will be examined and a path for utilization of this phenomenon in ME composites will be discussed. Magnetoelectric (ME) resonators are of significant interest for next generation near-dc magnetic field sensors, as the direct coupling of highly magnetostrictive ( FeCo- or FeGa-based alloys) and piezoelectric phases (AlN) enables high magnetic field sub-nT sensitivity with exceptionally low operational power requirements. This talk highlights several programs within the Materials Science & Technology Division at US Naval Research Laboratory focused on the investigation and understanding physics of these ferroic and multiferroic materials, and how current research presents another opportunity to advance acoustic transduction devices, magnetic sensors and electrically small antennas.<br/><br/>References:<br/>1. R. Ramesh and N.A. Spaldin, Nat. Mater. <b>6</b>, 21–29 (2007).<br/>2. J.M. Hu, Z. Li, L.Q. Chen, and C.W. Nan, Nat. Comm. <b>2</b>, 553 (2011).<br/>3. Finkel et al Sci. Rep. 5, 13770 (2015)<br/>4. M. Staruch et al., Applied Physics Letters 105, 152902 (2014)<br/>5. M. Staruch et al., Sci. Rep. <b>6</b>, 37429 (2016)