Using a first principles based, magnetic tight-binding total energy model, the magnetization energy and moments are computed for various ordered spin configurations in the high pressure polymorphs of iron (fcc, or γ-Fe, and hcp, or ϵ-Fe), as well ferromagnetic bcc iron (α-Fe). For hcp, a non-collinear, antiferromagnetic, spin configuration that minimizes unfavorable ferromagnetic nearest neighbor ordering is the lowest energy state and is more stable than non-magnetic ϵ iron up to about 75 GPa. Accounting for non-collinear magnetism yields better agreement with the experimental equation of state, in contrast to the non-magnetic equation of state, which is in poor agreement with experiment below 50 GPa.
@article{arxiv.cond-mat/0301615,
title = {Non-collinear magnetism in iron at high pressures},
author = {R. E. Cohen},
journal= {arXiv preprint arXiv:cond-mat/0301615},
year = {2009}
}