Structure analysis of high-pressure phase for skyrmion-hosting multiferroic Cu2OSeO3

TL;DR

This study investigates the high-pressure crystal structure of Cu2OSeO3, revealing modifications in molecular orientation and oxygen positions that may explain the increased magnetic transition temperature and stabilized skyrmion phase.

Contribution

It provides detailed structural insights into the high-pressure phase of Cu2OSeO3 using synchrotron X-ray diffraction and genetic algorithms, highlighting key atomic modifications.

Findings

Pyrochlore Cu network remains intact after transition

Significant changes in SeO3 orientation and oxygen positions

Potential link between structural changes and enhanced Tc

Abstract

Cu2OSeO3 is known as a unique example of insulating multiferroic compounds with skyrmion spin texture, which is characterized by the chiral cubic crystal structure at ambient pressure. Recently, it has been reported that this compound shows pressure-induced structural transition with large enhancement of magnetic ordering temperature Tc. In the present study, we have investigated the detailed crystal structure in the high pressure phase, by combining the synchrotron X-ray diffraction experiment with the diamond anvil cell and the analysis based on the genetic algorithm. Our results suggest that the original pyrochlore Cu network is sustained even after the structural transition, while the orientation of SeO3 molecule as well as the position of oxygen in the middle of Cu tetrahedra are significantly modified. The latter features may be the key for the reported enhancement of Tc and associated stabilization of skyrmion phase at room temperature.