The magnetization process in nickel single crystals: II

The general theory, given in a previous paper by Birss and Hegarty in 1966, of the magnetization process in nickel single crystals is used to obtain magnetization curves for (100) and (111) oblate spheroids, the applied megnetic field being in the plane of the spheroid in both cases. The curves obtained by numerical computation were first compared with Kaya's experimental data. This comparison is of limited value because a large part of Kaya's work was on unannealed specimens: for annealed specimens satisfactory agreement between theory and experiment is obtained. In order to extend the range of the comparison and to investigate the effect of annealing, torque measurements have been made on a (111) nickel disk at room temperature, and these are in good agreement with the theory. Torque measurements on the same disk at 131°K have also been made and these are used to show conclusively that the second anisotropy constant K 2 is negative.