Brillouin spectroscopy of nonlinear magnetoacoustic resonances in a layered YIG/GGG structure

Brillouin light scattering spectroscopy is used to visualize the spatial structure of magnetoacoustic resonances in an yttrium iron garnet (YIG) film on a gadolinium–gallium garnet (GGG) substrate under the strong influence of nonlinear processes of three magnon decay. It is shown that the decay processes result in the simultaneous excitation of magnetoacoustic resonances at two frequencies: those of the input signal and its half frequency. The distribution of coupled magnetic and elastic waves becomes much more complicated and the excitation threshold of magnetoacoustic resonances arises.