SUPEREXCHANGE IN A(II)B(VI) DILUTED MAGNETIC SEMICONDUCTORS WITH MN, FE AND CO IONS

A theory of superexchange, the dominant ion-ion spin interaction, for Mn-, Fe- and Go-based DMS is presented. The theory takes into account the band structure of A(II)B(VI) compounds, the orbital dependence of the hybridization and the intra shell correlations of the d-electrons, which are essential in the case of the non-S-state ions. The general formulae relating the superexchange to the band structure and the ioni c energy spectrum were obtained - the dominant part of the superexchan ge turns out to be inversely proportional to the square of the ionic s pin. This explains the observed increase in the average values of d-d exchange constants, when passing from Mn via Fe to Co ions in DMS.