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 effects are discussed in detail thereby providing the big picture of relevant interactions for this fascinating multiferroic compound.