The electric and magnetic properties of epitaxially grown A_0.5-xLa_xSr_0.5MnO₃ (A=Pr, Nd) thin film

The epitaxial (single crystal-like) Pr_0.4La_0.1Sr_0.5MnO_3 (PLSMO) and Nd_0.35La_0.15Sr_0.5MnO_3 (NLSMO) thin films are prepared and characterized, and the electric and magnetic properties are examined. We find that both PLSMO and NLSMO have their own optimum deposition temperature (T_\rm o) in their growing into epitaxial thin films. When the deposition temperature is higher than T_\rm o, a c-axis oriented but polycrystalline thin film grows; when the deposition temperature is lower than T_\rm o, the thin film tends to be a-axis oriented and also polycrystalline. The most important point is that for the epitaxial PLSMO and NLSMO thin films the electronic phase transitions are closely consistent with the magnetic phase transitions, i.e. an antiferromagnetic phase corresponds to an insulating state, a ferromagnetic phase corresponds to a metallic state and a paramagnetic phase corresponds to a semiconducting state, while for the polycrystalline thin films the electronic phase transitions are always not consistent with the magnetic transitions.