Spatial anisotropy of the exchange integrals in Mn-doped wurtzite-type semiconductors

Abstract

We propose an alternative explanation, as compared to one reported in the literature, to the experimentally observed spatial anisotropy ξ=ΔJ₁/J₁ⁱⁿ (ΔJ₁=J₁ⁱⁿ-J₁^out) of the nearest neighbor exchange integral J₁ in Mn-doped semiconductors with the wurtzite structure. We show that the main contribution to ξ is ferromagnetic and comes from a looped exchange path which involves two distinct anions. A comparison between our calculations, that use the results of photoemission spectroscopy as input parameters, and the available data for three wurtzite materials, CdS:Mn, CdSe:Mn, and ZnO:Mn, shows a good quantitative agreement between theory and experiment in the case of cadmium compounds and only a qualitative one in the case of ZnO:Mn.