Space-time correlation properties of the magnetization process and eddy current losses: Theory

Publisher Website
Google Scholar
Abstract
The relationship between eddy current losses and magnetization dynamics is investigated on general bases, starting directly from Maxwell equations. The intrinsically stochastic character of the magnetization process is conveniently dealt with by describing the magnetization rate İ(r,t) as a random sequence of elementary magnetization jumps, each corresponding to a sudden and localized displacement of a domain wall segment in the material. A general equation is obtained, in which the loss is expressed in terms of the energy spectrum ‖İ(k,ω)‖2 of İ(r,t). The loss calculation is thus reduced to the statistical problem of determining the energy spectrum of the random quantity İ(r,t) as a function of the shape and correlation properties of the elementary magnetization events. It turns out that the hysteresis loss is related to the internal structure of the elementary jumps, while the dynamic and anomalous losses are instead determined by the space-time correlation properties of the jump sequence. An explicit expression for the dynamic loss is obtained in the important case where the magnetization process is described as a Markov process, leading to a clear-cut, direct link between the loss and the fundamental quantities which characterize the magnetization dynamics at a microscopic level. The model predicts the exact value of the Pry and Bean loss, as a particular case corresponding to very specialized correlation properties of the jump sequence. However, the model permits one to deal with actually more general and realistic descriptions of the domain structure dynamics. We believe that future applications to practical cases will provide a deeper understanding of the physical origin of loss anomalies.

This publication has 15 references indexed in Scilit: