FREQUENCY-DEPENDENCE OF HYSTERESIS CURVES IN NONCONDUCTING MAGNETIC-MATERIALS

The problem of modelling the frequency dependence of hysteresis in magnetic materials is approached in a new way. The de magnetization curve, or hysteresis loop, is assumed to be the equilibrium position for the bulk magnetization. All microscopic processes which occur under the action of a time-varying field can be averaged to give a time dependent displacement from equilibrium, Delta M. In this paper, we examine the case where eddy current effects do not play a significant role, that is to say the model applies to ''non-conducting'' media. It is shown that Delta M obeys a damped simple harmonic motion equation. This means that the time dependence of the displacement magnetization Delta M is the Laplace transform of the field waveform. This enables the time dependence of the magnetization to be modelled, once the de hysteresis carve is known, with only two additional materials parameters of relaxation time and natural frequency. The model emerges as a natural extension of the theory of hysteresis.