Ferroelectricity in the 1 $\mu$C cm${}^{-2}$ range induced by canted antiferromagnetism in (LaMn${}_3$)Mn${}_4$O${}_{12}$

Pyroelectric current and magnetoelectric coupling measurements on polycrystalline samples of the quadruple perovskite (LaMn${}_3$)Mn${}_4$O${}_{12}$ give evidence of ferroelectricity driven by the antiferromagnetic ordering of the $B$-site Mn${}^{3+}$ ions at $T_{N,B}$=78 K with record values of remnant electric polarization up to $P$=0.56 $\mu$C cm${}^{-2}$. X-ray diffraction measurements indicates an anomalous behavior of the monoclinic $\beta$ angle at $T_{N,B}$, which suggests that $P$ lies in the $ac$-plane, where the moments are collinear, so we conclude that exchange striction is the mechanism of spin-driven ferroelectricity. Polarization values $\sim$3 $\mu$C cm${}^{-2}$ are expected in single crystals, which would open the avenue towards practical multiferroic applications.