Symmetry of multiferroicity in a frustrated magnet TbMn2O5

[[abstract]]Based on measurements of soft-x-ray magnetic scattering and symmetry considerations, we demonstrate that the magnetoelectric effect in TbMn2O5 arises from an internal field determined by S->q->×S->-q-> with S->q-> being the magnetization at modulation vector q->, whereas the magnetoelastic effect in the exchange energy governs the response to external electric fields. Our results set fundamental symmetry constraints on the microscopic mechanism of multiferroicity in frustrated magnets.y.[[fileno]]2010108010015[[department]]物理