Cu₂OSeO₃ turns trigonal with structural transformation and implications for skyrmions.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Magnetic skyrmions are particle-like magnetic structures crucial in spintronics.
• Skyrmion formation and properties are dictated by crystal structure symmetry.
• Copper oxide selenate (Cu2OSeO3) is a known material exhibiting skyrmionic behavior.

Purpose of the Study:

• To investigate the structural and magnetic properties of Cu2OSeO3 in nanoparticle form.
• To identify new polymorphs of Cu2OSeO3 and their influence on magnetic properties.
• To explore the relationship between size, crystal structure, and skyrmion type in Cu2OSeO3.

Main Methods:

• Synthesis and characterization of Cu2OSeO3 nanoparticles.
• Electron diffraction for structural analysis.
• Density functional theory (DFT) calculations for symmetry confirmation.

Main Results:

• Discovery of a new trigonal polymorph of Cu2OSeO3 (R3m space group) exclusively in nanoparticles.
• This polymorph exhibits C3v symmetry, similar to Néel-type skyrmion hosts.
• The new polymorph is likely stabilized by surface effects, suggesting size-dependent structural transitions.

Conclusions:

• Nanoparticle formation induces a new trigonal polymorph in Cu2OSeO3, stabilized by surface effects.
• Size-induced structural changes may drive a transition from Bloch-type to Néel-type skyrmions.
• Findings offer insights into controlling skyrmionic properties via size and structure manipulation in nanoscale systems.