Ferromagnetic superexchange in Cr-based diluted magnetic semiconductors

A theory of superexchange in Cr-based ${\mathit{A}}_{\mathrm{II}}$ ${\mathit{B}}_{\mathrm{VI}}$ diluted magnetic semiconductors (DMS’s) is presented. The spin interaction between ${\mathrm{Cr}}^{2+}$ ions, calculated numerically for zinc chalcogenides, exhibits properties unique in DMS’s, it is ferromagnetic, and depends on the relative orientations of the ionic Jahn-Teller distortions. We explain the origin of this unusual behavior and predict a ferromagnetic character of the superexchange in other Cr-based ${\mathit{A}}_{\mathrm{II}}$ ${\mathit{B}}_{\mathrm{VI}}$ DMS’s. © 1996 The American Physical Society.