The effect of disorder and short-range correlations on ferromagnetism in dilute magnetic semiconductors

We use the Dynamical Cluster Approximation (DCA) and double exchange model, coupling spin one-half holes to magnetic impurities, to study the ferromagnetic transition in semiconductors doped with transition metal magnetic ions. Our approach includes the effect of local dynamics as well as short-range correlations between the magnetic impurities. We systematically incorporate the effect of disorder in the impurity positional configurations with a new algorithm, based on the DCA, specific to dilute systems. This new algorithm serves as a replacement for the Traveling Cluster Approximation and Coherent Potential Approximation. We focus on the appearance of the impurity band and the development of the magnetization for a range of coupling strengths and hole and impurity concentrations. In addition, we discuss the effect of impurity clustering on the hole mobility and the ferromagnetic transition temperature. We conclude that the successful design of spintronic nanostructures based on ferromagnetic semiconductors must include an understanding and careful analysis of disorder and spatial correlations.