Magnetovolume effect, macroscopic hysteresis and moment collapse in the paramagnetic state of cubic MnGe under pressure

TL;DR

This study investigates pressure-induced magnetic and structural transitions in MnGe, revealing a two-step spin-moment collapse driven by magnetovolume coupling and elastic strains, with significant hysteresis and irreversibility.

Contribution

It provides detailed experimental evidence of a two-step spin-moment collapse in MnGe under pressure, highlighting the role of magnetovolume effects and elastic strains.

Findings

First-order transition with large hysteresis at ~7 GPa from high-spin to low-spin state.

Coexistence of spin-states and irreversibility due to elastic strains.

Complete spin-moment collapse at ~23 GPa.

Abstract

Itinerant magnets generally exhibit pressure induced transitions towards non magnetic states. Using synchrotron based X-ray diffraction and emission spectroscopy, the evolution of the lattice and spin moment in the chiral magnet MnGe was investigated in the paramagnetic state and under pressures up to 38 GPa. The collapse of spin-moment takes place in two steps. A first-order transition with a huge hysteresis around 7 GPa transforms the system from the high-spin at ambient pressure to a low-spin state. The coexistence of spin-states and observation of history-depending irreversibility is explained as effect of long-range elastic strains mediated by magnetovolume coupling. Only in a second transition, at about 23 GPa, the spin-moment collapses.