Strong Magneto-Elastic Coupling in Mn$_3$X (X = Ge, Sn)

TL;DR

This study reveals strong magnetoelastic coupling in Mn$_3$Ge and Mn$_3$Sn, with significant elastic tensor discontinuities at their antiferromagnetic transitions, and explores their potential for piezomagnetic applications.

Contribution

It provides the first detailed measurements of elastic tensors across magnetic transitions in Mn$_3$X compounds, highlighting their strong magnetoelastic effects and potential for piezomagnetism.

Findings

Large elastic discontinuities at Néel transitions indicate strong magnetoelastic coupling.

Discontinuities are nearly ten times larger in Mn$_3$Ge than Mn$_3$Sn.

Calculated pressure derivatives of Néel temperatures are 39 K/GPa for Mn$_3$Ge and 14.3 K/GPa for Mn$_3$Sn.

Abstract

We measure the full elastic tensors of Mn$_3$Ge and Mn$_3$Sn as a function of temperature through their respective antiferromagnetic phase transitions. Large discontinuities in the bulk moduli at the N\'eel transitions indicate strong magnetoelastic coupling in both compounds. Strikingly, the discontinuities are nearly a factor of 10 larger in Mn$_3$Ge than in Mn$_3$Sn. We use the magnitudes of the discontinuities to calculate the pressure derivatives of the N\'eel temperature, which are 39 K/GPa 14.3 K/GPa for Mn$_3$Ge and Mn$_3$Sn, respectively. We measured in-plane shear modulus $c_{66}$, which couples strongly to the magnetic order, in magnetic fields up to 18 T and found quantitatively similar behavior in both compounds. Recent measurements have demonstrated strong piezomagnetism in Mn$_3$Sn: our results suggest that Mn$_3$Ge may be an even better candidate for this effect.