Superexchange in insulators and semiconductors .2. the range of the exchange interaction

TLDR: In this paper, the authors discussed the range of exchange interactions in magnetic semiconductors and showed that the range depends strongly on the energy required to excite an electron from the fully occupied valence band to the empty magnetic d orbitals.

Abstract: In this paper we discuss the range of exchange interactions in magnetic semiconductors It is shown that the range depends strongly on the energy required to excite an electron from the fully occupied valence band to the empty magnetic d orbitals The range of the exchange interaction and of the spin-density distribution is the same when this excitation energy is large It is found that kinetic exchange and correlation exchange are the dominant contributions The usual perturbation theory breaks down when the dp excitation energy becomes of the order of the band width In this case one has to calculate the exchange interaction in a more rigorous way This limit is discussed using two-particle Green functions It is found that these results deviate strongly from the ones obtained using perturbation theory We derive a path model from an analysis of the effective transfer between two magnetic orbitals Such a model can explain the long-range exchange interactions reported in the last decades in a large number of magnetic semiconductors and semimagnetic semiconductors This path model can explain the anisotropy of long-range spin-density distributions found in doped semiconductors