Theory of Magnetic Switching of Ferroelectricity in Spiral Magnets

We propose a microscopic theory for magnetic switching of electric polarization (P) in the spin-spiral multiferroics by taking TbMnO(3) and DyMnO(3) as examples. We reproduce their phase diagrams under a magnetic field H(ex) by Monte Carlo simulation of an accurate spin model and reveal that competition among the Dzyaloshinskii-Moriya interaction, spin anisotropy, and spin exchange is controlled by the applied H(ex), resulting in magnetic transitions accompanied by reorientation or vanishing of P. We also discuss the relevance of the proposed mechanisms to many other multiferroics such as LiCu(2)O(2), MnWO(4), and Ni(3)V(2)O(4).