Dynamics of microscopic magnetization processes and magnetic losses (invited)

Abstract

To a first approximation only, microscopic magnetization processes giving rise to dynamic losses can be identified with uniform and continuous motions of domain walls. A new model has been developed which takes account of the spatial and temporal nonhomogeneities and of the stochastic character of the elementary loss mechanisms. The model is reviewed and further developments are discussed, which permit to evaluate with very good approximation local losses in sample regions with antiparallel domains, under the most general conditions of wall spacings and irregular motions. An expression is derived relating dynamic losses to the power spectrum of the time derivative of the flux linked to a square region of the lamination cross section having the side equal to its thickness d. This spectrum can be experimentally measured from the electromotive force induced between contact points on the specimen surface, or from the frequency analysis of the optical signal obtained by a Kerr type set-up, in which the lamination surface area under investigation is of the order of d2.