Effect of annealing on the transport process in manganite thin films

We study the electrical transport of an epitaxial La0.7Sr0.3Mn1.01O3.(delta) (LSMO) thin film and polycrystalline LSMO thin films annealed at different temperatures in association with the magnetoresistance. The polycrystalline films show a peak in the temperature-dependent resistivity near the Curie temperature and a slight increase at low temperatures. The zero-field-cooled and field-cooled magnetization of the polycrystalline films, which deviates from each other below the Curie temperature, indicates random magnetic configuration in the polycrystalline films. The temperature dependence of the resistivity is analyzed using expressions including resistivity contributions due to impurity scattering, spin-flip one particle scattering, and Coulomb blockade effect. The contributions of the spin-flip one particle scattering and the Coulomb blockade effect are found to decrease with increasing annealing temperature up to 1050 degrees C and increase above 1050 degrees C: the transport mechanism below 1050 degrees C is different from that above 1050 degrees C. We attribute the change in the transport mechanism at 1050 degrees C to the penetration of YSZ into grain boundaries of the polycrystalline thin films above 1050 degrees C.