Magnetic structure of the spin-1/2 frustrated quasi-one-dimensional antiferromagnet Cu3Mo2O9: Appearance of a partial disordered state

TL;DR

This study reveals the magnetic structure of Cu3Mo2O9, showing a partial disordered state with moments on dimers and chains, and discusses its implications for weak ferromagnetism and electric polarization.

Contribution

The paper determines the magnetic structure of Cu3Mo2O9 and identifies a partial disordered state using neutron diffraction, highlighting the role of frustration in this system.

Findings

Magnetic moments on dimers lie in the ac plane with magnitudes 0.50-0.74 μ_B.

Moments on chain sites are very small or absent.

The magnetic structure indicates a partial disordered state.

Abstract

We investigated the crystal and magnetic structures of the spin-1/2 frustrated antiferromagnet Cu3Mo2O9 in which the spin system consists of antiferromagnetic chains and dimers. The space group at room temperature has been reported to be orthorhombic Pnma (No. 62). We infer that the space group above TN = 7.9 K is monoclinic P2_1/m (No. 11) from the observation of reflections forbidden in Pnma in x-ray powder diffraction experiments at room temperature. We determined the magnetic structure of Cu3Mo2O9 in neutron powder diffraction experiments. Magnetic moments on dimer sites lie in the ac planes. The magnitudes are 0.50 - 0.74 mu_B. Moments on chain sites may exist but the magnitudes are very small. The magnetic structure indicates that a partial disordered state is realized. We consider the origin of the magnetic structure, weak ferromagnetism, and electric polarization.