Model for noncoherent magnetization reversal

Abstract

A model is presented for noncoherent magnetization reversal which reconciles experimental and theoretical observations. By its means, the saturation magnetization values of diverse materials and the fields required for their saturation are derived with precision. This includes polycrystalline Fe, Ni, Co, and several of their alloys selected at random from among those listed in the International Critical Tables. Data for these derivations are drawn from the tables referred to. The model is used to determine the energy required for magnetization by domain wall motion, as well as that needed for magnetization reversal in a single−crystal cobalt specimen. Data for these determinations are derived from published measurements made in fields whose strength varies from 0 to 9 kOe. Then, it is used to compute the value of the anisotropy field, HA, of an oriented Sm1/2Pr1/2Co5 specimen. Data for these computations are obtained from measurements made in fields whose strength is limited to 22 kOe. The results obtained support the hypothesis advanced that the strength of the applied field Ha required to saturate a uniaxial magnet in its easy direction of magnetization is given by the relationship, Ha=1/2HA, as K1 becomes much greater than K2. Here, K1 is the first−order and K2 is the second−order anisotropy constant. The phenomenon underlying this observation is explained and, in the process, it is shown that the anisotropy field HA required to saturate a completely oriented magnet and its single−crystal counterpart, in their hard directions, are exactly equal.