Magnetic and electrical transport properties of the La 0.67 Ca 0.33 Mn1–x O3 (x=0-0.16),which were prepared by the sol-gel method followed by sintering treatment at 1 450,1 100 and 900℃,respectively, were investigated.Experimental results show that,with the increase of x,the resistivity of samples increases and the insulator-metal transition temperature shifts towards lower temperature.Meanwhile,the intrinsic megnetoresistance effect is weakened and the extrinsic magnetoresistance is enhanced.For the samples with x=0.16 and 0.10 sintered at 1 100℃and 900℃,respectively,low field magnetoresistance as high as about 50%can be observed.Furthermore,for the samples sintered at 1 100℃and 900℃,the grain size is not only controlled by about sintering temperature,but also by the absence of Mn content x.
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