Loss contributions from correlations among irreversible movements of bloch walls

Theories on excess losses based on calculations of eddy currents due to the continuous and uniform motion of domain walls can only partly explain loss anomalies in G. O. FeSi. Furthermore, they completely fail to account for excess losses and non-linearity effects observed in many materials, where domain size is small compared to sample thickness. In the present work total losses are calculated considering also the contribution from irreversible movements of Bloch walls. The local magnetization is treated as a random function of time, characterized by a periodic and a non periodic component. Computation of losses is performed by convenient integration of the power spectrum of the voltage induced by the local magnetization variations. When the correlation among irreversible wall movements is taken into account, it is found that this provides a contribution to losses per cycle, which increases proportionally to the square root of the magnetizing frequency. Agreement is found with experimental behavior of losses in amorphous ferromagnets.