Effect of oxygen post-annealing on the magnetoresistance of highly epitaxial La0.7Ca0.3MnO3 thin films

Epitaxial La0.7Ca0.3MnO3 (LCMO) thin films have been deposited by high pressure DC sputtering technique on SrTiO3 substrates. As-grown films exhibit metal-insulator transition temperature (TMI) with values ranging from 131 to 220 K. The maximum value of the magnetoresistance is of about -77% in a magnetic field of 0.5 T for TMI=131 K. The same films, annealed in a pure oxygen atmosphere, exhibit transitions to a metallic state at temperatures ranging from 210 to 284 K. Transmission electron microscopy analyses show a coherent growth between film and substrate