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Magnetic Percolation and the Phase Diagram of the Disordered RKKY model

D. J. Priour, S. Das Sarma

cond-mat.mtrl-sciarXiv:cond-mat/0606532

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 the magnetic phase diagram as a function of the impurity moment density ni and the relative carrier concentration nc/ni. As evidenced by the diverging correlation length and magnetic susceptibility, the boundary between ferromagnetic (FM) and non-ferromagnetic (NF) 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 nc/ni>.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.

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