INDIRECT EXCHANGE INTERACTION IN DILUTED MAGNETIC SEMICONDUCTORS

The indirect exchange interaction between localized magnetic moments embedded in II-VI semiconductor hosts is theoretically studied. Based on realistic LCAO bands, the indirect exchange is calculated by the perturbation theory. In evaluating the second-order energy shift, a modified linear analytic tetrahedron method is used to perform the double Brillouin zone integration. From our results, two qualitative conclusions are reached. First, the indirect exchange is usually antiferromagnetic for the nearest few neighbours, becoming ferromagnetic as the distance between magnetic ions is increased. Second, the intrinsic cubic symmetry of the semiconductor host could induce strong directional dependence of the indirect exchange, and the sphericalization of the matrix element in the Brillouin zone might affect substantially the numerical accuracy of the calculated exchange coupling constant even when the band energy is essentially isotropic.