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采用溶胶-凝胶法制备了不同颗粒尺寸的La2/3Ca1/3Mn1-xCuxO3(x=0.04)系列试样。X射线衍射实验说明Cu掺杂和不同温度烧结没有改变晶体的结构。电阻-温度实验曲线表明,随颗粒尺寸的减小,半导体-金属转变温度(Tp)向低温方向移动。磁电阻曲线显示,随颗粒尺寸的减小,与颗粒晶界有关的磁电阻在25 K恒温、0.4 T低场下由25%增加到了51%。实验结果表明,在La2/3Ca1/3MnO3中少量Cu掺杂和小颗粒尺寸可以实质性地提高与颗粒晶界有关的低场磁电阻效应。
La2 / 3Ca1 / 3Mn1-xCuxO3 (x = 0.04) series of samples with different particle sizes were prepared by sol-gel method. X-ray diffraction experiments show that Cu doping and sintering at different temperatures do not change the crystal structure. The resistance-temperature experimental curves show that the semiconductor-to-metal transition temperature (Tp) shifts to lower temperatures as the particle size decreases. The magnetoresistance curves show that as the particle size decreases, the magnetoresistance associated with the grain boundaries increases from 25% to 51% at a constant temperature of 25 K and a low 0.4 T field. Experimental results show that a small amount of Cu doping and small particle size in La2 / 3Ca1 / 3MnO3 can substantially improve the low field magnetoresistance effect related to grain boundaries.