title: Phase diagram of the disordered RKKY model in dilute magnetic semiconductors.
abstract: We consider ferromagnetism in spatially randomly located magnetic moments, as in a diluted magnetic semiconductor, coupled via the carrier-mediated indirect exchange RKKY interaction. We obtain, via Monte Carlo calculations, the magnetic phase diagram as a function of the impurity moment density n(i) and the relative carrier concentration n(c)/n(i). As evidenced by the diverging correlation length and magnetic susceptibility, the boundary between ferromagnetic and nonferromagnetic phases constitutes a line of zero temperature critical points which can be viewed as a magnetic percolation transition. In the dilute limit, we find that bulk ferromagnetism vanishes for n(c)/n(i) >0.1. We also incorporate the local antiferromagnetic direct superexchange interaction between nearest neighbor impurities and examine the impact of a damping factor in the RKKY range function.
authors.affiliation: Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, MD 20742-4111, USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: Priour
authors.forename: S
authors.initials: S
authors.lastname: Das Sarma