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)O3–0.33PbTiO3 (PMN-PT). Due to the efficient elastic coupling at the interface, the electric-field-induced piezoelectric strain (ɛpiezo) 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 TC 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 TC. Moreover, we found that the resistivity of the film is most sensitive to ɛpiezo near TC and becomes less sensitive to ɛpiezo when the temperature is lower or higher than TC. 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.