Perovskite manganites hosting versatile multiferroic phases with symmetric and antisymmetric exchange strictions

Complete magnetoelectric (ME) phase diagrams of orthorhombic RMnO₃ with and without magnetic moments on the R ions have been established. Three kinds of multiferroic ground states, the $ab$-cycloidal, the $bc$-cycloidal, and the collinear E-type phases, have been identified by the distinct ME responses. The electric polarization of the E-type phase dominated by the symmetric spin exchange (Sᵢ·Sⱼ) is more than ten times as large as that of the $bc$-cycloidal phase dominated by the antisymmetric one (Sᵢ×Sⱼ) and the ME response is enhanced near the bicritical phase boundary between these multiferroic phases of different origins. These findings may provide generic features of the magnetically induced multiferroics.