The magnetization process in hexagonal ferromagnetic and ferrimagnetic single crystals

Abstract

Neel's 'theory of phases' is used to study the magnetization process in hexagonal ferromagnetic and ferrimagnetic single-crystal ellipsoids for which the six fold contribution to the magnetocrystalline anisotropy cannot be neglected. Simultaneous equations are presented, the solution of which yields the intensity and orientation of the mean sample magnetization and the various orientations of the saturation magnetization in the domains, for all values and orientations of the magnetic field. In some cases, the fractional contents of different types of domain can also be determined. Detailed consideration is given to the three special cases of oblate spheroids the minor ellipsoidal axes of which are parallel to the principal hexagonal axes when the magnetic field is in the plane of the sample. In addition, it is shown that the magnetization process is simplified for a number of special cases in which the magnetocrystalline anisotropy assumes particularly good simple forms. A comparison of the results of the theory with the limited experimental data available is made and, as an example of the application of the theory, the magnetization of gadolinium and dysprosium is calculated as a function of the intensity and direction of the magnetic field.