Discovering new magnetoelectric multiferroics is an exciting research area. Very recently, a collinear antiferromagnetic spin order was found to induce a ferroelectric polarization in a highly symmetric cubic perovskite ${\mathrm{LaMn}}_3{\mathrm{Cr}}_4{\mathrm{O}}_{12}$. This spin-driven ferroelectricity could not be explained by any of the existing multiferroic models. Here, we put forward a new model, i.e., anisotropic symmetric exchange, to understand this phenomenon, which was confirmed by density functional calculations and tight-binding simulations. Furthermore, our perturbation analysis shows that the anisotropic symmetric exchange term can be even stronger than the conventional contributions in some $5d$ systems. Our multiferroic model can not only explain the experimental results, but also may open a new avenue for exploring exotic magnetoelectric coupling effects.

• Received 26 December 2015
• Revised 5 April 2016

DOI:https://doi.org/10.1103/PhysRevB.93.174416