Mean-field approach to disorder effects on ferromagnetism in Ga1-xMnxAs

Using a numerical mean field treatment, we examine the onset of ferromagnetism and the nature of the ferromagnetic phase in Ga1-xMnxAs for charge carrier densities in the vicinity of the metal insulator transition. Our approach, which explicitly takes into account the positional disorder of the Mn ions, shows that the ferromagnetic transition temperature is significantly enhanced by the disorder. Concurrently, a very unusual temperature dependence of the magnetization is obtained in the ferromagnetic phase. (C) 2002 Elsevier Science B.V. All rights reserved.