Symmetry and Nonlinearity of Spin Wave Resonance Excited by Focused Surface Acoustic Waves

The use of a complex ferromagnetic system to manipulate GHz surface acoustic waves (SAWs) is a rich current topic under investigation, but the high-power nonlinear regime is under-explored. Focused SAWs are introduced, which provide a way to access this regime with modest equipment. The symmetry of the magneto-acoustic interaction can be tuned by interdigitated transducer design which can introduce additional strain components. Here, the impact of focused acoustic waves versus standard unidirectional acoustic waves in significantly enhancing the magnon-phonon coupling behavior is compared. Analytical simulation results based on the modified Landau-Lifshitz-Gilbert theory show good agreement with experimental findings. Nonlinear input power dependence of the transmission through the device is also reported. This experimental observation is supported by the micromagnetic simulation using mumax3 to model the nonlinear dependence. These results pave the way for extending the understanding and design of acoustic wave devices for the exploration of acoustically driven spin wave resonance physics.