Influence of the microwave amplitude on the spin current at the Pt/YIG interface

Spectra of spin current in a heterostructure, consisting of an epitaxial film of yttrium iron garnet Y$_{3}$Fe$_{5}$O$_{12}$ (YIG), grown on a gadolinium gallium garnet Gd$_{3}$Ga$_{5}$O$_{12}$ (GGG) substrate, and a platinum (Pt) film, have been investigated. The spin current, induced by microwave irradiation of the YIG film in the ferromagnetic-resonance mode and by the inverse spin Hall effect, was measured in the temperature range $T$ = 77–300 K at the microwave power and frequency varied in the ranges of 20 $\mu$W–50 mW and 2–9 GHz, respectively, to determine the influence of spin-wave resonances in YIG on the spectral characteristics of the spin current. It is found that the spin current amplitude due to spin-wave resonances of surface spin waves becomes comparable to the contribution from the ferromagnetic resonance with an increase in the microwave power at frequencies $f$ = 2–3 GHz.