THE LARGE MAGNETORESISTANCE PROPERTY OF LA0.5SR0.5COO3-X THIN-FILMS PREPARED BY PULSED-LASER DEPOSITION POSITION

High-quality (001) thin film La0.5Sr0.5CoO3-x (LSCO) has been prepared on (001) SrTiO3 substrates by pulsed laser deposition under different oxygen pressures with and without postannealing. C-axis expansion of the LSCO with reducing oxygen pressure was revealed. The electrical re sistivity increased over five orders of magnitude when oxygen pressure varied from 1.0 mbar (plus postannealing) to 10(-3) mbar. The negativ e magnetoresistance (n-MR) property as a function of temperature and o xygen pressure was investigated. Linear dependence of the n-MR ratio o n magnetic field and temperature was found and significant effect of o xygen stoichiometry on the n-MR was demonstrated. The film prepared at 650 degrees C and 0.1 mbar oxygen shows a n-MR ratio of -16% at 81 K under a field of only 0.2 T. (C) 1998 American Institute of Physics. [ S0003-6951(98)01134-6].