Ferrimagnetic 120$^\circ$ magnetic structure in Cu2OSO4

TL;DR

This study uncovers a ferrimagnetic 120-degree spin structure in Cu2OSO4, a frustrated magnetic insulator with a unique lattice, revealing insights into magnetic order and fluctuations at low temperatures.

Contribution

It reports the magnetic structure and properties of Cu2OSO4, identifying a novel ferrimagnetic 120-degree spin arrangement in a frustrated lattice.

Findings

Magnetic transition at 20 K confirmed by neutron scattering.

Ground state exhibits a 120-degree spin structure with ferrimagnetic order.

No lattice symmetry change observed down to 2 K.

Abstract

We report magnetic properties of a 3d$^9$ (Cu$^{2+}$) magnetic insulator Cu2OSO4 measured on both powder and single crystal. The magnetic atoms of this compound form layers, whose geometry can be described either as a system of chains coupled through dimers or as a Kagom\'e lattice where every 3rd spin is replaced by a dimer. Specific heat and DC-susceptibility show a magnetic transition at 20 K, which is also confirmed by neutron scattering. Magnetic entropy extracted from the specific heat data is consistent with a $S=1/2$ degree of freedom per Cu$^{2+}$, and so is the effective moment extracted from DC-susceptibility. The ground state has been identified by means of neutron diffraction on both powder and single crystal and corresponds to a $\sim120$ degree spin structure in which ferromagnetic intra-dimer alignment results in a net ferrimagnetic moment. No evidence is found for a change in lattice symmetry down to 2 K. Our results suggest that \sample \ represents a new type of model lattice with frustrated interactions where interplay between magnetic order, thermal and quantum fluctuations can be explored.