Theory of local magnetic anisotropy in amorphous alloys

The local magnetic anisotropy in amorphous transition metal alloys caused by local spin-orbit coupling has been studied by a perturbation treatment on the basis of a semi-empirical self-consistent Hartree-Fock approach for 55 different amorphous iron clusters (12-14 atoms). The corresponding structural units have been selected from a large amorphous model structure (2048 atoms). The numerical approach leads to a random distribution of the local easy directions and local anisotropy energies. The latter are of the same order of magnitude as those of uniaxial crystalline ferromagnets. The present theory is compared with the point-charge model of Cochrane et al. (1974), for the local anisotropy in amorphous alloys containing rare-earth atoms.