Effects of magnetic domain structure on low-field ferromagnetic resonance

초록

We investigated the history-dependent spin dynamics of a sputtered Co thin film using our broadband ferromagnetic resonance(FMR) spectrometer. Besides the usual FMR mode in the saturated state, we observed significant low-field dynamical responses with a hysteretic character in the unsaturated state, and their evolution and merging with the FMR mode as the excitation frequency is varied from 5.000 to 1.636 GHz. The microwave absorption process persists in the unsaturated state for frequencies higher than 1.868 GHz, such that the absorption minima occur at - 12 Oe on a down-field sweep and at +12 Oe on an up-field sweep. We believe that the study of microwave responses in the unsaturated regime using a broadband FMR measurement technique offer new method to investigate the magnetization processes that occur in magnetic thin films.