二相复合体La_(2/3)Ca_(1/3)MnO_3/xCuO的界面效应  

Boundary Effect of Two-Phase Composites La_(2/3)Ca_(1/3)MnO_3/xCuO

作　　者：李莉[1,2] 王桂英[1,2] 唐永刚[1,2] 刘鹏[1,2] 叶吾梅[1,2] 彭振生[1] 

机构地区：[1]宿州学院自旋电子与纳米材料安徽省重点实验室,安徽宿州234000 [2]宿州学院机械与电子工程学院,安徽宿州234000

出　　处：《稀有金属》2015年第6期510-515,共6页Chinese Journal of Rare Metals

基　　金：国家自然科学基金重点项目(19934003);安徽省教育厅自然科学研究重点项目(KJ2011A259;KJ2012Z404);宿州学院科研平台开放课题(2014YKF48;2014YKF49;2012 YKF 07)资助

摘　　要：用固相反应法制备二相复合体La2/3Ca1/3Mn O3/x Cu O（x=0,0.04,0.08,0.12,0.20,0.30）。用X射线衍射（XRD）图谱、扫描电子显微镜（SEM）照片检测样品的结构,通过零场冷和加场冷的电阻率-温度（ρ-T）曲线、磁电阻-温度（MR-T）曲线研究界面效应对电输运性质及磁电阻的影响。结果表明：样品形成完好的钙钛矿相和Cu O相;复合样品的颗粒比较均匀,颗粒大小约2μm,界面比较清晰;复合样品的ρ-T曲线出现双峰,x=0.04的样品电输运性质出现反常,它的电阻率既小于x=0的电阻率,也小于x=0.08的电阻率;复合样品的MR-T曲线也出现双峰,x=0.20,0.30的样品,0.8 T磁场下在50-250 K温区磁电阻不小于13.4%,实现了大温区且有较高磁电阻,有利于MR的实际应用。用影响电输运的多种因素的竞争很好地解释了界面效应。The two-phase composites La2/3Ca1/3MnO3/xCuO （x =0, 0. 04, 0.08, 0.12, 0.20, 0.30） were prepared by solid-state reaction method. The structure of the samples was detected by X-ray diffraction （XRD） and scanning electron microscope （ SEM ）, and the influences of boundary effect on electric transport property and magnetoresistance were studied through resistivity-temperature （p-T） curves in zero field and in magnetic field and magnetoresistance-temperature （MR-T） curves. The results indicated that intact perovskite phase and CuO phase formed in the samples ; the grain size of the composite samples was comparatively even, their diameter was about 2 μm, and the boundary was comparatively clear; the p-T curves of the composite samples exhibited double-peak, and the e- lectric transport property of the sample with x = 0.04 was abnormal because its resistivity was not only lower than that of x=0 but also lower than that of x = 0.08 ; the MR-T curves of the composite samples also exhibited double-peak, and magnetoresistance in the mag- netic field of 0.8 T and in the temperature range of 50 - 250 K for the samples with x = 0.20, 0.30 was not less than 13.4% , then comparatively large magnetoresistance in wide temperature range was realized, which was advantageous to the practical application of MR. Boundary effect was well explained by the competition among the many factors, which affected electric transport.

关 键 词：界面效应 电输运机制 MR效应 二相复合体 钙钛矿锰氧化物 

分 类 号：O482.5[理学—固体物理]