Influence of the Mn interstitial on the magnetic and transport properties of (Ga,Mn)As

We report on measurements of the hole density, ferromagnetic transition temperature T-C, and magnetization in a series of as-grown and annealed (Ga,Mn)As samples. Estimating the fraction of incorporated Mn occupying interstitial and substitutional sites allows a direct comparison of the predictions of mean field theory with experiment, and a determination of the magnetic moment per substitutional Mn. The saturation of T-C at high Mn concentration is consistent with the mean field prediction. The estimated magnetic moment per Mn is close to the expected 5mu(B) for all samples studied if an antiferromagnetic coupling between interstitial and substitutional Mn is assumed. (C) 2004 American Institute of Physics.