Magnetoelectric coupling in the cubic ferrimagnet Cu2OSeO3

TL;DR

This study explores magnetoelectric coupling in Cu2OSeO3, revealing significant magnetocapacitance and symmetry reduction upon magnetic ordering, with unique coupling mechanisms excluding spontaneous lattice strain.

Contribution

It demonstrates magnetoelectric coupling in a cubic ferrimagnet without involving spontaneous lattice strain, which is novel among such materials.

Findings

Significant magnetocapacitance develops below 60 K.

Magnetic ordering reduces symmetry from cubic to rhombohedral.

Lattice dimensions exclude spontaneous strain as the coupling mechanism.

Abstract

We have investigated the magnetoelectric coupling in the lone pair containing piezoelectric ferrimagnet Cu2OSeO3. Significant magnetocapacitance develops in the magnetically ordered state (TC = 60 K). We find critical behavior near TC and a divergence near the metamagnetic transition at 500 Oe. High-resolution X-ray and neutron powder diffraction measurements show that Cu2OSeO3 is metrically cubic down to 10 K but that the ferrimagnetic ordering reduces the symmetry to rhombohedral R3. The metric cubic lattice dimensions exclude a magnetoelectric coupling mechanism involving spontaneous lattice strain, and this is unique among magnetoelectric and multiferroic materials.