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用固态反应法制备了名义组分为 L a(1 + x) /3Ba(2 - x) /3Mnx Cu1 - x O3(0 .8≤ x≤ 1) 的系列试样。试样结构的单相性经粉末 X射线衍射分析而得以证实 ,且随 Cu的掺杂其结构由未掺杂时的立方对称性转变为正交对称性。输运实验表明 :所有试样均经历了半导体到金属的转变 ,但转变温度 TP随掺杂量增加而逐渐移向低温端 ;外加磁场大大增加了 TP附近的导电性 ,导致 TP附近最大磁电阻效应的出现
A series of samples with nominal composition L a (1 + x) / 3Ba (2 - x) / 3Mnx Cu1 - x O3 (0.8≤x≤1) were prepared by solid state reaction. The single phase property of the sample structure was confirmed by powder X-ray diffraction analysis, and its structure was changed from the cubic symmetry without undoped to the orthogonal symmetry with the doping of Cu. Transport experiments show that all the samples have undergone the transition from semiconductor to metal, but the transition temperature (TP) gradually shifts to low temperature with the increase of doping amount. The applied magnetic field greatly increases the electrical conductivity near TP, resulting in the maximum magnetoresistance The emergence of the effect