Schmitz-Antoniak, C.; Schmitz, D.; Borisov, P.; de Groot, F.M.F.; Stienen, S.; Warland, A.; Krumme, B.; Feyerherm, R.; Dudzik, E.; Kleemann, W.; Wende, H.: Electric in-plane polarisation in multiferroic CoFe2O4/BaTiO3 nanocomposite tuned by magnetic fields. Nature Communications 4 (2013), p. 2051/1-8

Ferrimagnetic CoFe2O4 nanopillars embedded in a ferroelectric BaTiO3 matrix are known as magnetoelectrically coupled model systems with potential for technical applications operating at room temperature and free of any resource-critical rare-earth element. In particular, the electric properties can be tuned by magnetic elds as shown for instance in our study of the strain-mediated coupling between the two subsystems by means of soft x-ray absorption spectroscopy and its associated linear dichroism. We demonstrate for the rst time that an in-plane magnetic eld breaks the tetragonal symmetry of the (1,3)-type CoFe2O4/BaTiO3 structures and discuss it in terms of o -diagonal magnetostrictive-piezoelectric coupling. It creates staggered in-plane components of the electric polarisation, which are stable even at magnetic remanence due to hysteretic behaviour of structural changes in the BTO matrix. Competing mechanisms of clamping and relaxation e ffects are discussed in detail thereby providing the big picture of relevant interactions for this fascinating multiferroic compound.