Cu2OSeO3 Turns Trigonal with Structural Transformation and Implications for Skyrmions

TL;DR

This study discovers a new trigonal polymorph of Cu2OSeO3 in nanoparticles, revealing size-induced structural changes that influence skyrmion types, and suggests surface effects stabilize this phase, impacting magnetic properties.

Contribution

It reports a novel trigonal phase of Cu2OSeO3 in nanoparticles and links size and surface effects to skyrmion type transformation, advancing understanding of nanoscale magnetic materials.

Findings

New trigonal Cu2OSeO3 polymorph identified in nanoparticles

Surface effects likely stabilize the new structural phase

Size-induced structural changes may switch skyrmion types

Abstract

The formation and characteristics of magnetic skyrmions are strongly governed by the symmetry of the underlying crystal structure. In this study, we report the discovery of a new trigonal polymorph of Cu2OSeO3, observed exclusively in nanoparticles. Electron diffraction and density functional theory calculations confirm its R3m space group, sharing C3v symmetry with N\'eel-type skyrmion hosts. This polymorph is likely stabilized by surface effects, suggesting that size-induced structural changes may drive a transformation from Bloch-type to Neel-type skyrmions in Cu2OSeO3. This hypothesis is consistent with prior unexplained observations of Neel-type skyrmions at the surfaces of bulk crystals, which may result from surface-specific structural distortions. Overall, these findings provide insights into the interplay between size, structure, and magnetism, opening pathways for controlling skyrmionic properties in nanoscale systems.