Investigating the magnetic ground state of the skyrmion host material Cu$_{2}$OSeO$_{3}$ using long-wavelength neutron diffraction

TL;DR

This study uses long-wavelength neutron diffraction to analyze the magnetic structures of Cu$_{2}$OSeO$_{3}$, revealing detailed spin textures, phase transitions, and ferrimagnetic clusters, advancing understanding of skyrmion host materials.

Contribution

It provides new insights into the magnetic ground state and spin textures of Cu$_{2}$OSeO$_{3}$ using neutron diffraction, highlighting the presence of ferrimagnetic clusters in different phases.

Findings

Observation of magnetic satellites around (0-11) peak

Identification of helical, conical, and skyrmion lattice phases

Detection of ferrimagnetic clusters in ground state

Abstract

We present long-wavelength neutron diffraction data measured on both single crystal and polycrystalline samples of the skyrmion host material Cu$_{2}$OSeO$_{3}$. We observe magnetic satellites around the $(0\bar{1}1)$ diffraction peak not accessible to other techniques, and distinguish helical from conical spin textures in reciprocal space. We confirm successive transitions from helical to conical to field polarised ordered spin textures as the external magnetic field is increased. The formation of a skyrmion lattice with propagation vectors perpendicular to the field direction is observed in a region of the field-temperature phase diagram that is consistent with previous reports. Our measurements show that not only the field-polarised phase but also the helical ground state are made up of ferrimagnetic clusters instead of individual spins. These clusters are distorted Cu tetrahedra, where the spin on one Cu ion is anti-aligned with the spin on the three other Cu ions.