Gigantic magnetic field induced polarization and magnetoelectric coupling in a ferrimagnetic oxide CaBaCo 4 O 7 V. Caignaert 1 , A. Maignan 1 *, K. Singh 1,5 , Ch. Simon 1 , V. Pralong 1 , B. Raveau 1 , J.F. Mitchell 2 H. Zheng 2 , A. Huq 3 , and L. Chapon 4 1 Laboratoire CRISMAT, UMR 6508 CNRS/ENSICAEN, 6 bd du Maréchal Juin F-14050 CAEN Cedex 4 – France. 2 Argonne National Laboratory MSD 223 9700 S. Cass Avenue Argonne, IL 60439, USA 3 Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA 4 Institut Laue-Langevin 6, rue Jules Horowitz - BP 156 F- 38042 Grenoble Cedex 9, France Abstract The single crystal study of CaBaCo 4 O 7 , a non collinear ferrimagnet (T C =64K), with a polar orthorhombic space group (Pbn2 1 ) between 4 K and 293 K, shows the appearance below T C of a large electric polarization along its c  axis, reaching 17 mC.m -2 at 10K. At 62.5 K, a magnetic field driven giant variation of polarization, P(9T) - P(0T) = 8 mC/m 2 , is observed. Moreover, the present magnetoelectric measurements are fully consistent with the m’m2’ magnetic point group, strongly supporting that this oxide is also ferrotoroidic. This ferrimagnetic oxide, which belongs to the “114” structural family, opens an avenue for the search of new magnetoelectrics. * Antoine Maignan Laboratoire CRISMAT, ENSICAEN/CNRS, 6 boulevard du Maréchal Juin, 14050 Caen cedex 4 - France antoine.maignan@ensicaen.fr Tel: 02.31.45.26.04 Fax: 02.31.95.16.00