Highly conductive perovskite La0.5Sr0.5CoO3 thin films were grown on (012) LaAlO3 by pulsed-laser deposition at different substrate temperatures. Magnetoresistance (MR) measurements show only a negative effect for the films grown at a temperature of 800 °C. However, a positive MR effect was found for the films grown at lower temperatures of 400 and 500 °C. The sign of the magnetoresistance changed from positive to negative near 150 K under an applied magnetic field of 5.0 T, and the largest positive MR of 2.6% was obtained at a temperature of 4.2 K for the film grown at 500 °C. Low-temperature magnetic hysteresis of the films was also studied, and it is suggested that the scattering of the carrier at the domain boundary may lead to the positive-MR effect.

We have investigated the crystallization of amorphous Y–Ba–Cu–O films with pulsed laser irradiation. The Y–Ba–Cu–O films were prepared on Si (001) substrates by pulsed laser deposition at room temperature. The microstructure and surface morphology of the films during the crystallization process were studied by x-ray diffraction and scanning electron microscopy. Micro or submicro Y–Ba–Cu–O crystalline particles can be obtained with variant laser pulses and energy densities. The particles have half-spherical or even spherical shapes on the film surfaces, and the saturated particle sizes were found to be determined by the film thickness.