| AVS 65th International Symposium & Exhibition | |
| Magnetic Interfaces and Nanostructures Division | Thursday Sessions |
| Session MI+2D-ThM |
| Session: | Magnetism at the Nanoscale |
| Presenter: | Kevin Fitzell, University of California, Los Angeles |
| Authors: | K. Fitzell, University of California, Los Angeles C.R. Rementer, University of California, Los Angeles N. Virushabadoss, University of Texas at Dallas M.E. Jamer, National Institute of Standards and Technology (NIST) A. Barra, University of California, Los Angeles J.A. Borchers, National Institute of Standards and Technology (NIST) B.J. Kirby, National Institute of Standards and Technology (NIST) G.P. Carman, University of California, Los Angeles R.M. Henderson, University of Texas at Dallas J.P. Chang, University of California, Los Angeles |
| Correspondent: | Click to Email |
The ability to reduce the size of antennae would enable a revolution in wearable and implantable electronic devices. Multiferroic antennae, composed of individual ferromagnetic and piezoelectric phases, could reduce antenna size by up to five orders of magnitude through the efficient coupling of magnetization and electric polarization via strain. This strategy requires a low-loss magnetic material with strong magnetoelastic coupling at high frequency.
Galfenol (Fe84Ga16 or FeGa) is a promising candidate material due to its large magnetostriction (>200 ppm), large piezomagnetic coefficient (>3 ppm/Oe), and high stiffness (>50 GPa), but it is highly lossy in the GHz regime. On the other hand, Permalloy (Ni81Fe19 or NiFe) is a soft magnetic material that has very low loss in the GHz regime (ferromagnetic resonance linewidth <20 Oe) but almost no magnetostriction. In this work, nanoscale laminates containing alternating layers of FeGa and NiFe were fabricated via DC magnetron sputtering to combine the complementary properties of the two magnetic phases. Optimized magnetic laminates were shown to exhibit a small coercive field (<20 Oe), narrow ferromagnetic resonance linewidth (<40 Oe), and high relative permeability (>400) (Rementer et al., 2017). In addition, optical magnetoelastic measurements of these laminates confirmed the presence of strong magnetostriction; relative to single-phase FeGa, these laminates represent a threefold enhancement in magnetostriction at saturation and up to a tenfold enhancement at low magnetic fields.
Multiferroic composites incorporating these magnetic laminates were then studied via polarized neutron reflectometry, demonstrating coherent rotation of the individual layers’ magnetization with an applied electric field across distances much larger than the exchange length of either material. Micromagnetic and finite element simulations support the experimental results, showing coherent rotation of the magnetization with only small deviations with thicker NiFe layers. Subsequent integration of these laminates into strain-mediated multiferroic antennae confirmed the absorption of electromagnetic and acoustic waves, showing great promise for the use of FeGa/NiFe laminates in micro-scale communications systems.