Epitaxial growth of La_0.7Ba_0.3MnO₃ thin films on MgO substrates: Structural, magnetic, and transport properties

We report on structural, magnetic, and transport properties of La_0.7Ba_0.3MnO₃ thin films, epitaxially grown on MgO substrates. Despite the quite similar structural features if compared to crystalline manganite films, our samples show a metal-insulator transition temperature of about 200 K, sizeably lower than the bulk-value (T_MI≃345 K). Moreover, the magnetotransport properties show the absence of saturation in the magnetoresistance and localization phenomena at low temperatures (T≪30 K). The temperature behavior of the magnetization shows a Curie temperature T_c value above room temperature, ruling out effects due to oxygen deficiency. All these findings are analyzed in terms of possible physical mechanisms related to the growth in the presence of large mismatch between film and substrate lattice parameters.