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.
@article{arxiv.1008.5226,
title = {Cupric chloride CuCl2 as an S=1/2 chain multiferroic},
author = {S. Seki and T. Kurumaji and S. Ishiwata and H. Matsui and H. Murakawa and Y. Tokunaga and Y. Kaneko and T. Hasegawa and Y. Tokura},
journal= {arXiv preprint arXiv:1008.5226},
year = {2010}
}