The effect of reducing time on the magnetoresistance of manganite La 0.67 Sr 0.20 Cu 0.10 □ 0.03 MnO 3 at a temperature of 30°C

La0.67Sr0.20Cu0.10□0.03MnO3 ("□" representing cation vacancy) polycrystalline manganite powder was synthesized by sol-gel method, which we used as parent materials. After reduced in hydrogen atmosphere for 30 and 60 minutes at a temperature of 400°C, the series bulk samples were obtained by sintering in argon atmosphere for 12 hours at 1100°C. The structure, electrical and magnetic properties, and colossal magnetoresistance of samples were researched in detail. Experiment results indicate that under an applied magnetic field of 1.8 T, the two bulk samples sintered in Ar atmosphere for 12 hours at 1100°C, with the powder reduced for 30 and 60 minutes in 400°C hydrogen atmosphere for La0.67Sr0.20Cu0.10□0.03MnO3 parent powders, respectively, have the stable MR (11.0±0.3)% and (10.0±0.5)% in temperature region from 270 K to 330 K. this is important for the potential application of this kind of magnetoresistance materials.