| AVS 66th International Symposium & Exhibition | |
| Magnetic Interfaces and Nanostructures Division | Wednesday Sessions |
| Session MI+2D-WeA |
| Session: | Emerging Multifunctional Magnetic Materials II |
| Presenter: | Adrian Acosta, University of California, Los Angeles |
| Authors: | A. Acosta, University of California, Los Angeles K. Fitzell, University of California, Los Angeles C. Dong, Northeastern University M. Zurbuchen, University of California, Los Angeles N.X.S. Sun, University of California, Los Angeles J.P. Chang, University of California, Los Angeles |
| Correspondent: | Click to Email |
Magnetoelectric materials provide the ability to efficiently control magnetism with electric fields, which is key to circumvent the size and efficiency limitations of traditional electric dipole antennas. Strain-mediated multiferroic antennas, composed of individual ferromagnetic and piezoelectric phases, have recently generated a lot of interest due to the potential to reduce the size of antennas by up to 5 orders of magnitude through the coupling of magnetization and electric polarization via strain at the interface. However, this requires a low-loss magnetic material with strong magnetoelastic coupling at high frequencies.
Galfenol (Fe81Ga19 or FeGa) is a promising candidate material due to its large magnetostriction (~275 ppm in polycrystalline bulk) and large piezomagnetic coefficient (>2 ppm/Oe) but is highly lossy at high microwave frequencies. Previously, nanoscale laminates were fabricated via DC magnetron sputtering of FeGa with NiFe as an interlayer material resulting in a composite with a small coercive field (<20 Oe), narrow FMR linewidth (<35 Oe), and high relative permeability (>1000) [1]. In this work, the enhancement in soft magnetic properties is correlated to the microstructure of these composites by TEM analysis where the nanolayering strategy promotes the formation smaller grain sizes. Optical magnetostriction measurements displayed an enhanced magnetostriction beyond that expected from averaging the individual FeGa and NiFe phases, indicating an interfacial contribution present leading to increase of the overall magnetostriction. The magnetostriction sensitivity peaks at a lower magnetic field (23 Oe for FeGa/NiFe multilayers vs 56 Oe for FeGa). To delineate the impact of the microstructure of FeGa on the soft and functional magnetic properties, FeGa was sputter deposited onto several materials (NiFe, Ta, Cu, and Al2O3) as underlayers on a Si substrate which can directly influence the polycrystalline structure and enhance its soft magnetic properties [2]. XRD and AFM are used to show the dependence of the coercivity, FMR linewidth, and magnetostriction on the texture, internal stress, grain size, and surface roughness of the FeGa film with the different underlayer materials.
Integration of these engineered composites into a strain-mediated multiferroic shear wave antenna design further demonstrates the potential of FeGa-based laminates for use in microwave communications systems for implantable medical devices.
References:
[1] Rementer, C. R., et al. (2017). Applied Physics Letters 110(24): 242403.
[2] Jung, H., et al. (2003). Journal of Applied Physics 93(10): 6462-6464.