The ferroelectric polarization of triangular-lattice antiferromagnets induced by helical spin-spiral order is not explained by any existing model of magnetic-order-driven ferroelectricity. We resolve this problem by developing a general theory for the ferroelectric polarization induced by spin-spiral order and then by evaluating the coefficients needed to specify the general theory on the basis of density functional calculations. Our theory correctly describes the ferroelectricity of triangular-lattice antiferromagnets driven by helical spin-spiral order, and incorporates known models of magnetic-order-driven ferroelectricity as special cases.
@article{arxiv.1109.1328,
title = {General Theory for the Ferroelectric Polarization Induced by Spin-Spiral Order},
author = {H. J. Xiang and E. J. Kan and Y. Zhang and M. -H. Whangbo and X. G. Gong},
journal= {arXiv preprint arXiv:1109.1328},
year = {2011}
}