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 ni and the relative carrier concentration nc/ni. 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 nc/ni>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.
- Publication:
-
Physical Review Letters
- Pub Date:
- September 2006
- DOI:
- 10.1103/PhysRevLett.97.127201
- arXiv:
- arXiv:cond-mat/0606532
- Bibcode:
- 2006PhRvL..97l7201P
- Keywords:
-
- 75.50.Pp;
- 71.15.-m;
- 75.10.Nr;
- 75.30.Hx;
- Magnetic semiconductors;
- Methods of electronic structure calculations;
- Spin-glass and other random models;
- Magnetic impurity interactions;
- Condensed Matter - Materials Science;
- Condensed Matter - Disordered Systems and Neural Networks
- E-Print:
- 5 pages, 3 figures