Damping dependence in microwave assisted magnetization reversal

This letter reports a demonstration of microwave assisted magnetization reversal (MAMR) in a CoFeB film and the damping dependence in MAMR through the measurement of ferromagnetic resonance (FMR). Spin-pumping in non-ferromagnetic/ferromagnetic films provides a large range variation of Gilbert damping constants in magnetic samples when changing the thickness of non-ferromagnetic layers without changing the ferromagnetic film. An evident dependence of switching fields on the damping constant is observed in the presence of microwaves. The trend of the experimental data is well reproduced by a numerical simulation based on the Landau–Lifshitz–Gilbert equation. The result indicates that the large damping decreases the efficiency of microwaves in reducing the magnetization switching field.