A Study Of The Disordered Dilute Magnetic Semiconductors Zn1-Xcrxse And Zn1-Xfexse

We report on the electronic structure and exchange interactions in the dilute magnetic semiconductors Zn1-xCrxSe and Zn1-xFexSe. 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 Zn1-xFexSe at all concentrations. For Zn1-xCrxSe 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 Zn1-xFexSe. However, as in the case of Zn1-xCrxSe, when the chemical and magnetic interactions are strongly coupled this simple scaling is no longer observed.