Appl. Phys. Lett. 78,
3493 (2001)
Influence of the local As antisite distribution on ferromagnetism in (Ga,Mn)As
S. Sanvito, and Nicola A. Hill
The effect of the inclusion of As antisites in the diluted magnetic semiconductor
(Ga,Mn)As is studied within the density functional theory in the local
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
mediate the long-range ferromagnetic order. In contrast, when two Mn ions
are coupled through only one As ion, the ferromagnetic and antiferromagnetic
states are comparable in energy. In this case, the magnetic ground state
depends on: (i) the position of the As antisites relative to the Mn, and
(ii) the As antisite concentration. We explain our results using a model
of competing antiferromagnetic super exchange and ferromagnetic double
exchange via localized Zener carriers.