ANISOTROPY OF THE MAGNETIZATION OF ISOLATED FE2+ IONS IN II-VI COMPOUNDS

In wurtzite-structure semiconductors, the low-field magnetization of isolated Fe2+ ions for magnetic induction B over arrow pointing right along the trigonal axis, c, of the crystal exceeds that when B over arrow pointing right is at right angles to c. This anisotropy is reversed as the magnetic field intensity is increased. In this paper, we show that the reversal of the anisotropy occurs at different magnetic field intensities depending on the orientation of B over arrow pointing right in a plane perpendicular to c. From a numerical study in conjunction with an expansion of the angular variation of the magnetization in terms of combinations of spherical harmonics invariant under the operations of the symmetry group, C3v, of the ion site, we conclude that the magnetic field at which the reversal occurs is lowest if B over arrow pointing right lies on a sigma(v) plane and largest if B over arrow pointing right is normal to one of these planes.