Ferroelectricity in the MagneticE-Phase of Orthorhombic Perovskites

We show that the symmetry of the spin zigzag chain $E$ phase of the orthorhombic perovskite manganites and nickelates allows for the existence of a finite ferroelectric polarization. The proposed microscopic mechanism is independent of spin-orbit coupling. We predict that the polarization induced by the $E$-type magnetic order can potentially be enhanced by up to 2 orders of magnitude with respect to that in the spiral magnetic phases of ${\mathrm{TbMnO}}_3$ and similar multiferroic compounds.