Epitaxial growth and interface strain coupling effects in manganite film/piezoelectric-crystal multiferroic heterostructures

We constructed multiferroic structures by epitaxially growing colossal magnetoresistive La0.7Sr0.3MnO3 (LSMO) thin films on piezoelectric single-crystal substrates of composition 0.67Pb(Mg1/3Nb2/3)O-3-0.33PbTiO(3) (PMN-PT). Due to the efficient elastic coupling at the interface, the electric-field-induced piezoelectric strain (epsilon(piezo)) in the PMN-PT substrate is effectively transferred. to the LSMO film, giving rise to a remarkable modulation of the lattice strain, resistivity, and Curie temperature T-C of the LSMO film. Particularly, it was found that the magnetic field has an opposite effect on the strain-tunability of resistivity above and below T-C. Moreover, we found that the resistivity of the film is most sensitive to epsilon(piezo) near T-C and becomes less sensitive to epsilon(piezo) when the temperature is lower or higher than T-C. These, together with the well fitted resistivity data into a phenomenological model based on coexisting phases, demonstrate that the phase separation is crucial to understand the strain-mediated multiferroic properties in manganite film/PMN-PT structures. (C) 2011 Elsevier B.V. All rights reserved.