GIANT MAGNETORESISTANCE EFFECT AND TEMPERATURE-DEPENDENCE OF MAGNETORESISTANCE IN LA2 3CA1/3MNOZ THIN-FILM/

Magnetoresistance in the temperature region from 300 K to liquid heliu m temperature has been measured on good (100) oriented La2/3Ca1/3MnOz thin films prepared by d.c. magnetron sputtering on ZrO2 (100) substra tes. It is found that there appears a resistance peak at about T-p sim ilar or equal to 72 K at zero magnetic field, and this peak moves to h igher temperature with increasing field H, and R decreases simultaneou sly. However, the magnetoresistance ratio MR = delta R/R(H)=(R(O)/R(H) )/R(H) has a different temperature dependence. There are also MR peaks , but the temperature of maximum MR is at about 25 K which does not ch ange with ; changing external magnetic field. The heat treatment (anne aled at 700 degrees C in 10(5)Pa O-2 for 30 min) will make R reduce dr amatically and has an effect on the temperature dependence of R and it s MR.