Origin of spiral-spin order:picture Da(rn)·[SnXS+l]E=-元x+kx2:2o(S×S) Cooperative GdFeO,distortion Mn Mn Spiral DM Polarization Dzyaloshinsky,J.Phys.Chem.Solids 4,241(1958);Moriya,Phys.Rev.120,91(1960)Origin of spiral-spin order: picture Mn O Mn O Mn Spiral Spiral DMDM Polarization Polarization Cooperative GdFeO Cooperative GdFeO33distortion distortion Dzyaloshinsky, J. Phys. Chem. Solids 4, 241 (1958); Moriya, Phys. Rev.120, 91 (1960) P E=- x+kx 2:  ~ (S S)