Cupric chloride CuCl2 as an S=1/2 chain multiferroic

TL;DR

This study demonstrates that CuCl2, an S=1/2 chain antiferromagnet, exhibits multiferroic behavior with spiral-spin order, showing magnetoelectric coupling consistent with the inverse Dzyaloshinskii-Moriya model, even under quantum fluctuations.

Contribution

It provides the first example of a non-chalcogen based spiral-spin multiferroic with detailed magnetoelectric behavior analysis.

Findings

Ferroelectric polarization emerges with helimagnetic order.

Magnetic field induces spin-flop transition and suppresses ferroelectricity.

Spin-spiral plane rotation correlates with polarization direction change.

Abstract

Magnetoelectric properties were investigated for an S=1/2 chain antiferromagnet CuCl2, which turns out to be the first example of non-chalcogen based spiral-spin induced multiferroics. Upon the onset of helimagnetic order propagating along the b-axis under zero magnetic field (H), we found emergence of ferroelectric polarization along the c-axis. Application of H along the b-axis leads to spin-flop transition coupled with drastic suppression of ferroelectricity, and rotation of H around the b-axis induces the rotation of spin-spiral plane and associated polarization direction. These behaviors are explained well within the framework of the inverse Dzyaloshinskii-Moriya model, suggesting the robustness of this magnetoelectric coupling mechanism even under the strong quantum fluctuation.