Magnetotransport properties of epitaxial strain-less La0.7Ba0.3MnO3 thin films

We have fabricated La0.7Ba0.3MnO3 (LBMO) thin films by a pulsed laser deposition technique using a low partial pressure (10(-2) mbar) of O-2+5% O-3. In order to study the role of oxygen content in the transport properties, the temperature dependence of the resistivity has been measured as a function of the temperature and the time of a post-annealing process. Strain-less LBMO thin films deposited on SrTiO3 substrates show a metal insulator transitions temperature T-MI similar or equal to 345 K (equal to that found in bulk material). A T-2.5-power law has been measured in R(T) at low temperature, supporting the disorder-induced single magnon scattering scenario. At high temperature (T > T-MI) an activated behavior characteristic of polaronic carriers has been measured. Magnetotransport properties show a metal-like behavior and a negative magnetoresistance (MR) in the whole temperature range. With an external magnetic field of 70 kOe, the MR reaches the maximum value of 170% at about 320 K. (c) 2007 American Institute of Physics.