Microwave-induced DC Signal in a Permalloy Thin Strip at Low Applied Magnetic Field

We investigated the ferromagnetic resonance signals in a polycrystalline permalloy thin strip under in-plane low static magnetic field. A series of DC voltages, which contain ferromagnetic resonance or spin wave resonance signals, were measured by inducing microwave frequencies greater than 10 gigahertz. The resonant signals measured in low magnetic field show different properties from those detected in high field condition. Based on the theory of DC effects in ferromagnetic resonance and the experimental data of anisotropic magnetoresistance, a quantitative model was proposed. We found that the shape anisotropy significantly affects magnetization, and distorts the resonant signals in low field condition.