Ferroelectricity induced by acentric spin-density waves in YMn$_2$O$_5$
arXiv:cond-mat/0511174 · doi:10.1103/PhysRevLett.96.097601
Abstract
The commensurate and incommensurate magnetic structures of the magnetoelectric system YMn$_{2}$O$_{5}$, as determined from neutron diffraction, were found to be spin-density waves lacking a global center of symmetry. We propose a model, based on a simple magneto-elastic coupling to the lattice, which enables us to predict the polarization based entirely on the observed magnetic structure. Our data accurately reproduce the temperature-dependence of the spontaneous polarization, in particular its sign reversal at the commensurate-incommensurate transition.
10 pages, 3 figures, 1 table