High Power Ferromagnetic Resonance in Thin Permalloy Films - The Steady State Response, Threshold Modifications, and Magnon Scattering

Nonlinear magnetization dynamics in thin metallic ferromagnetic films plays an essential role in magnetic switching and spin torque transfer. The high power magnetodynamic response in Permalloy thin films in the vicinity of the FMR peak is examined. The main results are (1) a large shift of the FMR peak position and the development of a strong asymmetry in the absorption profile as the microwave power is increased and (2) a saturation response at fixed field that is gradual, with no clear threshold instability onset point. The microwave measurements were done on evaporated polycrystalline Permalloy (Ni82Fe18) films with thicknesses of 35, 57, and 74 nm. The microwave cavity measurements were done at a nominal frequency of 9.11 GHz, with the static field H and the linearly polarized microwave field both in plane..