Large-angle magnetization dynamics investigated by vector-resolved magnetization-induced optical second-harmonic generation

Abstract

We examine the relationship between nonlinear magnetic responses and the change in the Gilbert damping parameter α for patterned and unpatterned thin Permalloy films when subjected to pulsed magnetic fields. An improved magnetization-vector-resolved technique utilizing magnetization-induced optical second-harmonic generation was used to measure magnetization dynamics after pulsed-field excitation. The magnetization excitations were achieved with pulsed fields aligned parallel to the hard axis of thin permalloy (Ni80Fe20) films while a dc bias field is applied along the easy axis. At low bias fields, α was inversely related to the bias field, but there was no significant reduction in the absolute value of the magnetization, as might be expected if there was significant spin-wave generation during the damping process. We discuss the discrepancies between data obtained by ferromagnetic resonance, whereby spin-wave generation is prevalent, and pulsed-field studies, with the conclusion that fundamental differences between the two techniques for the excitation of the ferromagnetic spin system might explain the different proclivities toward spin-wave generation manifest in these two experimental methods.