Disorder and ferromagnetism in diluted magnetic semiconductors

We have investigated the interplay between disorder and ferromagnetism in III1-xMnxV semiconductors. Our study is based on a model in which S = 5/2 Mn local moments are exchange coupled to valence-band holes that interact via Coulomb interactions with each other, with ionized Mn acceptors, and with the antisite defects present in these materials. We find quasiparticle participation ratios consistent with a metal-insulator transition that occurs in the ferromagnetic state near xsimilar to0.01. By evaluating the distribution of exchange mean fields at Mn moment sites, we provide evidence in favor of the applicability of impurity-band magnetic-polaron and hole-fluid models on insulating and metallic sides of the phase transition, respectively.