Electric polarization induced by Neel order without magnetic superlattice: experimental study of Cu3Mo2O9 and numerical study of a small spin cluster

TL;DR

This study demonstrates that antiferromagnetic order in a low-dimensional, frustrated spin system can induce electric polarization without magnetic superlattices, combining experimental phase diagram analysis and numerical modeling.

Contribution

It provides experimental evidence and numerical modeling showing electric polarization induced by Neel order in a frustrated spin system without magnetic superlattices.

Findings

Electric polarization is induced by antiferromagnetic order in Cu3Mo2O9.

Colossal magnetocapacitance occurs near the tricritical point at 10 T and 8 K.

Charge redistribution in a small spin cluster explains the polarization mechanism.

Abstract

We clarify that the antiferromagnetic order in the distorted tetrahedral quasi-one dimensional spin system induces electric polarizations. In this system, the effects of the low dimensionality and the magnetic frustration are expected to appear simultaneously. We obtain the magnetic-field-temperature phase diagram in Cu3Mo2O9 by studying the dielectric constant and the spontaneous electric polarization. Around the tricritical point at 10 T and 8 K, the change of the direction in the electric polarization causes a colossal magnetocapacitance. We calculate the charge redistribution in the small spin cluster consisting of two magnetic tetrahedra to demonstrate the electric polarization induced by the antiferromagnetism.