We report density functional studies of the Fe1−xCuxSe alloy done using supercell and coherent potential approximation methods. Magnetic behavior was investigated using the disordered local moment approach. We find that Cu occurs in a nominal d10 configuration and is highly disruptive to the electronic structure of the Fe sheets. This would be consistent with a metal insulator transition due to Anderson localization. We further find a strong cross over from a weak moment itinerant system to a local moment magnet at x≈0.12. We associate this with the experimentally observed jump near this concentration. Our results are consistent with the characterization of this concentration dependent jump as a transition to a spin-glass.
@article{arxiv.0910.3599,
title = {Electronic Structure, Localization and Spin-State Transition in Cu-substituted FeSe: Fe$_{1-x}$Cu$_x$Se},
author = {S. Chadov and D. Schärf and G. H. Fecher and C. Felser and L. Zhang and D. J. Singh},
journal= {arXiv preprint arXiv:0910.3599},
year = {2013}
}