Modelling the effect of excitation frequency on the shape of hysteresis loop in permalloy

. In the paper the effect of excitation frequency on the shape of hysteresis loops in permalloy was investigated and modelled. Two models were considered - one based on effective field with term depending on magnetization derivative, and the other based on viscosity-related equation superimposed over a static hysteresis model. In the first approach only a qualitative agreement with measurements was obtained, whereas the second one offers a better agreement, although it exhibits specific anvil-like distortion in the second and the fourth quadrant of the H-8 coordinate system. The "anvils" are a direct consequence of singularity in the viscosity equation when saturation is approached.