Gigantic magnetic-field-induced polarization and magnetoelectric coupling in a ferrimagnetic oxide CaBaCo4O7

Below ${T}_{C}$, the single-crystal study of CaBaCo${}_{4}$O${}_{7}$, a noncollinear ferrimagnet (${T}_{C}=64$ K) with a polar orthorhombic space group (Pbn2${}_{1}$) between 4 and 293 K, shows a large change in the electric polarization along its $\stackrel{P\vec}{c}$ axis reaching $\ensuremath{\Delta}P=17$ mC/m${}^{2}$ at 10 K. At 62.5 K, a magnetic-field-driven giant variation in polarization $P$(9 T) \ensuremath{-} $P$(0 T) $=$ 8 mC/m${}^{2}$ is observed. Moreover, the present magnetoelectric measurements are fully consistent with the $m$\ensuremath{'}$m$2\ensuremath{'} magnetic point group. This ferrimagnetic oxide, which belongs to the ``114'' structural family, opens an avenue for the search for new magnetoelectrics.