Foldover ferromagnetic resonance and damping in permalloy microstrips

We have investigated the foldover ferromagnetic resonance in ferromagnetic permalloy (Py) microstrips by microwave photovoltage and photoresistance techniques. We have found that the linewidth of the nonlinear ferromagnetic resonance is strongly dependent on the precession angle of magnetization. Therefore, we have revised the Anderson-Suhl instability, which enables us to quantitatively describe the foldover effect in Py microstrips. The calculation from this proposed model shows excellent agreement with experimental data.