Magnetization Changes and Losses in Conducting Ferromagnetic Materials

Abstract

This paper discusses magnetization changes and the losses associated with them in bulk metallic magnetic materials, whose behavior is determined by eddy currents. The various reversal mechanisms in these materials, the conditions under which each is operative, the losses associated with each, and the dependence of the behavior on various parameters are discussed. The eddy-current-limited motion of an isolated domain wall is first considered. The behavior in increasingly large fields and the transition to a collapsing cylindrical or double planar wall in high fields are examined. The hysteresis loops and losses calculated for the isolated wall, the collapsing cylindrical wall, and the double planar wall are discussed for various conditions of excitation. The effects brought about in the low-frequency case by the presence of more than one wall are described, reviewing the results of theoretical calculations for multiple-wall configurations and the experimental results obtained with the superposed-high-frequency technique. The predictions of classical eddy-current theory and the ``eddy-current anomaly'' are discussed. The importance of selecting the correct model for the circumstances is illustrated by some data from the literature.