The temperature dependence of the magnetization and spin-polarization at the Fermi level is investigated for half-metallic ferromagnets. We reveal a new mechanism, where the hybridization of states forming the half-metallic gap depends on thermal spin fluctuations and the polarization can drop abruptly at temperatures much lower than the Curie point. We verify this for NiMnSb by ab-initio calculations. The thermal properties are studied by mapping ab-initio results to an extended Heisenberg model which includes longitudinal fluctuations and is solved by a Monte Carlo method.
@article{arxiv.cond-mat/0512277,
title = {Thermal collapse of spin-polarization in half-metallic ferromagnets},
author = {M. Lezaic and Ph. Mavropoulos and J. Enkovaara and G. Bihlmayer and S. Blügel},
journal= {arXiv preprint arXiv:cond-mat/0512277},
year = {2007}
}