Local structural distortions and Mn random distributions in (Ga,Mn)As: A first-principles study

Abstract

The effect of random distribution of Mn atoms on the electronic and magnetic properties of ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ with $x=0.0625$ is studied with Vienna ab initio simulation package. We use a $2\ifmmode\times\else\texttimes\fi{}2\ifmmode\times\else\texttimes\fi{}2$ supercell, in which 64 atoms are included, and two Mn atoms substitute Ga positions. Five different Mn-Mn configurations are considered. Local structural relaxations show that the bond lengths of Mn-As are smaller than those of the nearby Ga-As. The total-energy calculation indicates that because of the inhomogeneous spatial distribution of holes, the ferromagnetic interaction between two Mn ions strongly depends on the direction along the two Mn ions. The inhomogeneous distribution of Mn atoms makes the holes stay in slightly stronger localized states. The value of magnetic moments and their spatial distributions are slightly affected by random distribution of Mn atoms.