Large-angle magnetization dynamics investigated by vector-resolved magnetization-induced optical second-harmonic generation
Thomas Gerrits, Thomas J. Silva, John P. Nibarger, Theo Rasing
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 pulse-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.