Magnetoelastic coupling in iron

TL;DR

This study investigates the magnetoelastic coupling in iron using ab-initio calculations, revealing how lattice distortions influence magnetic interactions and explaining the anti-Invar behavior in gamma-iron.

Contribution

It provides a detailed ab-initio analysis of exchange interactions and their dependence on lattice distortions in alpha- and gamma-iron, highlighting the strong coupling between crystal and magnetic structures.

Findings

Exchange interactions in gamma-Fe are highly sensitive to lattice distortions.

Tetragonal deformation can induce ferromagnetic ground states.

The results explain the anti-Invar behavior in gamma-Fe.

Abstract

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.