Stochastic model for magnetic hysteresis

Abstract

A model of ferromagnetic hysteresis is presented, in which the different microscopic magnetization processes are reduced to the motion of a single domain wall in a random energy landscape. The equivalent pinning field acting on the domain wall is assumed to be a space-dependent stochastic process described by a set of coupled Langevin-type equations. The model is inspired by the one proposed by Néel for the description of hysteresis in the Rayleigh region, but it is more general, as it predicts both the static and the dynamic hysteresis loops, as well as their fine structure (Barkhausen effect). The model properties were investigated by computer simulations. In the low field limit, the Rayleigh law is verified, with coefficients depending on the stochastic properties of the pinning field, whereas at high fields the loop behavior is dominated by demagnetizing fields. The results obtained for the energy losses show that the separation of losses into the hysteresis and the dynamic components is a general property of this model. Furthermore, we numerically verified that in our model there is a complete decoupling of the dissipation effects due to the presence of the pinning field (inner disorder) and to the dynamics of the domain wall.