Multiferroicity in LiCu2O2 single crystals is studied using resonant soft x-ray magnetic scattering, hard x-ray diffraction, heat capacity, magnetic susceptibility, and electrical polarization. Two magnetic transitions are found at 24.6 K (T1) and 23.2 K (T2). Our data are consistent with a sinusoidal spin structure at T2<T<T1 and with a helicoidal spin structure at T<T2 giving rise to ferroelectricity. Surprisingly, above T2 the correlation lengths of the spin structures increase as the temperature increases with dramatic changes of ~42% along the c-axis. Our results demonstrate the interplay of the geometrical frustration and the electronic and magnetic polarizations.
@article{arxiv.0808.0281,
title = {Multiferroicity in the spin-1/2 quantum matter of LiCu2O2},
author = {A. Rusydi and I. Mahns and S. Mueller and M. Ruebhausen and S. Park and Y. J. Choi and C. L. Zhang and S-W. Cheong and S. Smadici and P. Abbamonte and M. v. Zimmermann and G. A. Sawatzky},
journal= {arXiv preprint arXiv:0808.0281},
year = {2009}
}