Giant magneto-elastic coupling in a metallic helical metamagnet

TL;DR

This study reveals a giant magneto-elastic coupling in CoMnSi, where thermal changes significantly alter atomic distances, indicating a new mechanism for magnetoelastic effects independent of strong spin-orbit interactions.

Contribution

The paper demonstrates the largest observed thermal evolution of inter-atomic distances in a metallic magnet and introduces a new mechanism for magnetoelastic coupling.

Findings

Inter-atomic distances change by up to 2% with temperature.

The magnetoelastic effect occurs without large spin-orbit coupling.

Competing exchange interactions and anisotropic thermal expansion explain the phenomena.

Abstract

Using high resolution neutron diffraction and capacitance dilatometry we show that the thermal evolution of the helimagnetic state in CoMnSi is accompanied by a change in inter-atomic distances of up to 2%, the largest ever found in a metallic magnet. Our results and the picture of competing exchange and strongly anisotropic thermal expansion that we use to understand them sheds light on a new mechanism for large magnetoelastic effects that does not require large spin-orbit coupling.