Tuning the structure of Skyrmion lattice system Cu2OSeO3 under pressure

TL;DR

This study investigates how external pressure induces structural phase transitions in Cu2OSeO3, affecting its magnetic phases like skyrmion lattice, through experimental and theoretical analysis.

Contribution

It provides the first detailed analysis of pressure-induced structural changes and their impact on magnetic properties in Cu2OSeO3 using combined experimental and theoretical methods.

Findings

Cubic phase transforms to monoclinic above 7 GPa.

Further transition to triclinic phase occurs above 11 GPa.

Decompression leads to a new monoclinic structure.

Abstract

The insulating ferrimagnet Cu2OSeO3 shows a rich variety of phases such as skyrmion lattice and helical magnetism controlled by interplay of different exchange interactions which can be tuned by external pressure. In this work we have investigated pressure-induced phase transitions at room temperature using synchrotron based x- ray diffraction and Raman scattering measurements. With first-principles theoretical analysis, we show that spin-spin exchange couplings in the ambient cubic phase are affected notably by hydrostatic pressure. The ambient cubic phase transforms to a monoclinic phase above 7 GPa and then to the triclinic phase above 11 GPa. Emergence of new phonon modes in the Raman spectra confirms these structural phase transitions. Notably, upon decompression, the crystal undergoes transition to a new monoclinic structure. Atomic coordinates have been refined in the low pressure cubic phase to capture the Cu-tetrahedra evolution responsible for the earlier reported magnetic behavior under pressure. Our experiments will motivate further studies of its emergent magnetic behavior under pressure.