A study of the disordered dilute magnetic semiconductors Zn(1-x)Cr(x)Se and Zn(1-x)Fe(x)Se.

We report on the electronic structure and exchange interactions in the dilute magnetic semiconductors Zn(1-x)Cr(x)Se and Zn(1-x)Fe(x)Se. The exchange energies and densities of states were obtained using the layer Korringa-Kohn-Rostoker method and the coherent potential approximation. We find that the dominant exchange in all cases is the super-exchange mechanism, and it is found to be antiferromagnetic for Zn(1-x)Fe(x)Se at all concentrations. For Zn(1-x)Cr(x)Se the exchange interaction changes from ferromagnetic to antiferromagnetic at high concentrations due to the ability of Cr in the antiferromagnetic state to more effectively bond with the host structure. The strength of the super-exchange coupling in the tight binding model is linear in concentration, which we observe for Zn(1-x)Fe(x)Se. However, as in the case of Zn(1-x)Cr(x)Se, when the chemical and magnetic interactions are strongly coupled this simple scaling is no longer observed.