High Power Ferromagnetic Resonance, Resonance Saturation, and Spin Wave Instability in Thin Permalloy Films

The two objectives of this new work were to establish quantitative techniques for high power FMR measurements on metallic ferromagnetic films and obtain reliable data on the damping and nonlinear loss parameters that play a role in high speed switching. The main results are (1) quantitative FMR profiles as a function of input power, (2) a determination of the SW instability threshold microwave field amplitudes (hcrl) as a function of the static external field (H) over the entire FMR profile, and (3) a full analysis of the h_crit vs. H data in terms of second order Suhl theory, suitably modified for thin films. Item (3) yields the critical modes and spin wave damping parameters applicable to resonance saturation (RS). These results represent the first measurements and analysis of Suhl processes over the full FMR profile for metal films.