Influence of the local As antisite distribution on ferromagnetism in (Ga, Mn)As

The effect of the inclusion of As antisites in the diluted magnetic semicon ductor (Ga, Mn)As is studied within the density functional theory in the lo cal spin density approximation. In the case of the homogeneous distribution of Mn ions, we find that the ferromagnetism is weakened by the presence of the antisites. This is due to the compensation of the free holes which med iate the long-range ferromagnetic order. In contrast, when two Mn ions are coupled through only one As ion, the ferromagnetic and antiferromagnetic st ates are comparable in energy. In this case, the magnetic ground state depe nds on: (i) the position of the As antisites relative to the Mn, and (ii) t he As antisite concentration. We explain our results using a model of compe ting antiferromagnetic super exchange and ferromagnetic double exchange via localized Zener carriers. (C) 2001 American Institute of Physics.