Symmetry of multiferroicity in a frustrated magnet TbMn2O5.

摘要: Based on measurements of soft-x-ray magnetic scattering and symmetry considerations, we demonstrate that the magnetoelectric effect in ${\mathrm{TbMn}}_{2}{\mathrm{O}}_{5}$ arises from an internal field determined by ${\stackrel{\ensuremath{\rightarrow}}{S}}_{\stackrel{\ensuremath{\rightarrow}}{q}}\ifmmode\times\else\texttimes\fi{}{\stackrel{\ensuremath{\rightarrow}}{S}}_{\ensuremath{-}\stackrel{\ensuremath{\rightarrow}}{q}}$ with ${\stackrel{\ensuremath{\rightarrow}}{S}}_{\stackrel{\ensuremath{\rightarrow}}{q}}$ being magnetization at modulation vector $\stackrel{\ensuremath{\rightarrow}}{q}$, whereas magnetoelastic exchange energy governs response to external electric fields. Our results set fundamental constraints microscopic mechanism multiferroicity frustrated magnets.