Impact of magnetism on screw dislocations in body-centered cubic chromium

TL;DR

This study uses ab initio calculations to explore how magnetism affects screw dislocations in body-centered cubic chromium, revealing minimal impact on structural properties but some influence on glide barriers.

Contribution

It provides the first detailed comparison of dislocation properties in magnetic and non-magnetic phases of chromium, highlighting the role of magnetic order in dislocation behavior.

Findings

Magnetism causes magnetic faults in 1/2 111 dislocations but not in 100 dislocations.

Dislocation energies are marginally affected by magnetic ordering.

Peierls energy barriers are similar for both slip systems, with lower barriers in the magnetic phase.

Abstract

The influence of magnetism on the properties of screw dislocations in body-centered cubic chromium is investigated by means of ab initio calculations. Screw dislocations having Burgers vectors 1/2 111 and 100 are considered, following experimental observations showing activity for both slip systems. At low temperature, chromium has a magnetic order close to antiferromagnetism along 100 directions, for which 1/2 111 is not a periodicity vector. Hence, dislocations with Burgers vectors 1/2 111 generate magnetic faults when shearing the crystal, which constrain them to coexist and move pairwise, leading to dissociated 111 super-dislocations. On the other side, 100 is a periodicity vector of the magnetic order of chromium, and no such magnetic fault are generated when 100 dislocations glide. Dislocation properties are computed in the magnetically ordered and non magnetic phases of chromium for comparison purposes. We report a marginal impact of magnetism on the structural properties and energies of dislocations for both slip systems. The Peierls energy barrier opposing dislocation glide in {110} planes is comparable for both 1/2 111 {110} and 100 {110} slip systems, with lower Peierls stresses in the magnetically ordered phase of chromium.