Disorder-enhanced spin polarization in diluted magnetic semiconductors

Abstract

We present a theoretical study of diluted magnetic semiconductors that includes spin-orbit coupling within a realistic host band structure and treats explicitly the effects of disorder due to randomly substituted Mn ions. While spin-orbit coupling reduces the spin polarization by mixing different spin states in the valence bands, we find that disorder from Mn ions enhances the spin polarization due to formation of ferromagnetic impurity clusters and impurity bound states. The disorder leads to large effects on the hole carriers which form impurity bands as well as hybridizing with the valence band. For Mn doping $0.01\ensuremath{\lesssim}x\ensuremath{\lesssim}0.04$, the system is metallic with a large effective mass and low mobility.