1202.1575 (X. Z. Lu et al.)

Giant Ferroelectric Polarization of CaMn7O12 Induced by a Combined
Effect of Dzyaloshinskii-Moriya Interaction and Exchange Striction    [PDF]

X. Z. Lu, M. -H. Whangbo, Shuai Dong, X. G. Gong, H. J. Xiang

By extending our previous general spin-current model of ferroelectric
polarization to any spin dimers, we investigate the causes for the helical
magnetic order and the giant ferroelectric polarization on the basis of density
functional calculations. The giant ferroelectric polarization is caused by the
symmetric exchange striction due to the canting of the Mn4+ spin arising from
its strong Dzyaloshinskii-Moriya (DM) interaction. CaMn7O12 exhibits a novel
magnetoelectric coupling mechanism in which the magnitude of the polarization
is governed by the exchange striction, but the direction of the polarization by
the chirality of the helical magnetic order.

View original: http://arxiv.org/abs/1202.1575