On and Off-Resonance Spin Wave/Surface Acoustic Wave Coupling Measured Using Brillouin Light Scattering

Surface acoustic waves (SAWs) have a much longer propagation distance than most spin waves, especially in metallic ferromagnets. If spin waves can be effectively coupled to SAWs they can travel farther and SAW/spin wave coupling also offers new opportunities for energy efficient spin wave generation. Here we have used an interdigital transducer (IDT) on a piezoelectric substrate to produce a SAW at 1.8 GHz and we have studied the coupling of the SAW to spin waves in a 20 nm thick Ni thin film using Brillouin light scattering (BLS). A strong signal is observed at the driving frequency f that varies in intensity as a function of the applied magnetic field. At fields where f overlaps with the spin wave manifold an additional peak is observed at 2f that is not present at higher fields, which indicates that nonlinear process are active. Measurements were also performed at multiple locations on the nickel pad to characterize how the spin wave decays with distance.