Magnetic properties of 3d impurities substituted in GaAs

We have calculated the magnetic properties of substituted 3d impurities (Cr-Ni) in a GaAs host by means of first-principles electronic structure calculations. We provide a novel model explaining the ferromagnetic long-range order of III-V dilute magnetic semiconductors. The origin of the ferromagnetism is shown to be delocalized spin-uncompensated As dangling-bond electrons. Besides the quantitative prediction of the magnetic moments, our model provides an understanding of the half-metallicity, and the rise of the critical temperature with the impurity concentration. (author)