  We report on the deformation of microwave absorption spectra and of the
inverse spin Hall voltage signals in thin film bilayers of yttrium iron garnet
(YIG) and platinum at high microwave power levels in a 9.45-GHz TE011 cavity.
As the microwave power increases from 0.15 to 200 mW, the resonance field
shifts to higher values, and the initially Lorentzian spectra of the microwave
absorption intensity as well as the inverse spin Hall voltage signals become
asymmetric. The contributions from opening of the magnetization precession cone
and heating of YIG cannot well reproduce the data. Control measurements of
inverse spin Hall voltages on thin-film YIG|Pt systems with a range of line
widths underscore the role of spin-wave excitations in spectral deformation.
