Forward volume magnetoacoustic spin wave excitation with micron-scale spatial resolution

Abstract

The interaction between surface acoustic waves (SAWs) and spin waves (SWs) in a piezoelectric-magnetic thin film heterostructure yields potential for the realization of novel microwave devices and applications in magnonics. In the present work, we characterize magnetoacoustic waves in three adjacent magnetic micro-stripes made from CoFe + Ga, CoFe, and CoFe + Pt with a single pair of tapered interdigital transducers (TIDTs). The magnetic micro-stripes were deposited by focused electron beam-induced deposition and focused ion beam-induced deposition direct-writing techniques. The transmission characteristics of the TIDTs are leveraged to selectively address the individual micro-stripes. Here, the external magnetic field is continuously rotated out of the plane of the magnetic thin film and the forward volume SW geometry is probed with the external magnetic field along the film normal. Our experimental findings are well explained by an extended phenomenological model based on a modified Landau–Lifshitz–Gilbert approach that considers SWs with nonzero wave vectors. Magnetoelastic excitation of forward volume SWs is possible because of the vertical shear strain ɛ xz of the Rayleigh-type SAW.

Chiral Magnetoacoustics

“…Because of magnetoelastic coupling to ε kl and magneto-rotation coupling to ω xz [28][29][30], the free energy of the magnetic thin film is modulated with the frequency ω = 2πf and wave vector k kx of the SAW [27,31]. More general situations, including the outof-plane orientation of M and other SAW modes, are discussed in references [27, [32][33][34].…”

Spatial analysis of multi-frequency SAW beams excited by slanted IDTs on ZnO-SiC heterostructures

“…This spatial control is particularly effective in microfluidics [7], where it has improved particle-sorting selectivity [8,9] and droplet-splitting [10]. The unique combination of spatial control and tunable frequency also provides important and unique probes of electron states at the quantum scale [11] and enables targeted magnetoacoustic excitation of spin-wave systems [12]. For such applications, it is necessary to make a thorough characterization of slanted IDTs capable of exciting SAWs in the GHz frequency range on the materials of interest and to identify possible factors that may limit their performance.…”