Exchange interactions in {\alpha}- and {\gamma}-Fe are investigated within an ab-initio spin spiral approach. We have performed total energy calculations for different magnetic structures as a function of lattice distortions, related with various cell volumes and the Bain tetragonal deformations. The effective exchange parameters in {\gamma}-Fe are very sensitive to the lattice distortions, leading to the ferromagnetic ground state for the tetragonal deformation or increase of the volume cell. At the same time, the magnetic-structure-independent part of the total energy changes very slowly with the tetragonal deformations. The computational results demonstrate a strong mutual dependence of crystal and magnetic structures in Fe and explain the observable "anti-Invar" behavior of thermal expansion coefficient in {\gamma}-Fe.
@article{arxiv.1111.4432,
title = {Magnetoelastic coupling in iron},
author = {S. V. Okatov and Yu. N. Gornostyrev and A. I. Lichtenstein and M. I. Katsnelson},
journal= {arXiv preprint arXiv:1111.4432},
year = {2011}
}