Investigation of Diverse Magnetic Materials via Acoustically Driven Ferromagnetic Resonance*

Magnetoelastic coupling has been exploited to detect FMR using surface acoustic waves(SAWs), a technique known as ADFMR. GHz-frequency SAWs are produced and detected electrically using pairs of interdigital transducers(IDTs). A magnetic film is placed in the path of the SAWs, which can then interact with magnetic moments via magnetoelastic coupling. Absorption of the SAWs occurs at FMR, modulating the measured output. Landau-Lifshitz-Gilbert theory describes the interaction in terms of the external magnetic field with a characteristic four-lobe pattern, from which the magnetic anisotropy field, FMR resonance field, and magnetoelastic coupling coefficient can be inferred.
We study the effects of a variety of magnetic materials including Ni, FeCo, FeGaB, and FeCoSiB, to examine the dependence of ADFMR patterns on material parameters and geometries. We use a range of SAW frequencies from ~300 to 2000 MHz to explore spectral effects of the IDT design on transduction efficiency, and the frequency dependence of the resonance field. We also calculate the FMR linewidth and quality factor- figures of merit useful for determining the efficacy of future ADFMR devices.