La_(0.67)Ca_(0.33-x)Ba_xMnO_3的电输运性质反常及磁电阻温度稳定性  

Abnormal Electric Transport Property and Temperature Stability of Magnetoresistance in La_(0.67)Ca_(0.33-x)Ba_xMnO_3

作　　者：李莉[1,2] 王桂英[1,2] 罗鹏[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》2016年第5期446-452,共7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(KJ2013A245);宿州学院科研平台开放课题(2014YKF49;2014YKF48);安徽省优秀青年人才支持计划重点项目(gxyq ZD2016341)资助

摘　　要：用固相反应法制备La_(0.67)Ca_(0.33-x)Ba_xMn O_3(x=0,0.10,0.15,0.20,0.25)系列样品,烧结温度为1200℃。通过X射线衍射(XRD)图谱,扫描电子显微镜(SEM)照片、零场和加场下的电阻率-温度(ρ-T)曲线,磁电阻-温度(MR-T)曲线,研究Ba^(2+)替代Ca^(2+)的La_(0.67)Ca_(0.33-x)Ba_xMnO_3的电输运性质及磁电阻温度稳定性。结果表明:随Ba^(2+)替代量的改变晶体结构发生变化,x=0的样品为立方结构,x=0.10的样品为正交结构,x=0.15,0.20,0.30的样品为六方结构。x=0.10样品的电输运性质出现反常,它的电阻率不仅比未掺Ba的La_(0.67)Ca_(0.33)Mn O_3高出60倍,也比高掺Ba样品的电阻率高出几倍,随Ba^(2+)替代量的增加电阻率逐渐下降,用掺Ba引起的晶格结构变化及Mn O_6八面体畸变进行解释;高掺Ba样品实现了室温附近磁电阻温度稳定性,x=0.15的样品在187~246 K温区磁电阻为(8.91±0.42)%,x=0.20的样品在230~290 K温区磁电阻为(6.07±0.32)%,x=0.25的样品在320 K以下直至50 K温区磁电阻均大于14%。在0.8 T磁场下在室温附近产生磁电阻的温度稳定性有利于MR效应的实际应用。磁电阻温度稳定性机制是,钙钛矿的磁电阻是体相内双交换作用产生的本征磁电阻与界面自旋相关散射或自旋极化隧穿产生的低场磁电阻的叠加,制备样品时控制烧结温度(1200℃),尽量提高低场磁电阻,两种磁电阻叠加产生磁电阻温度稳定性。La0.67Ca0.33-xBaxMnO3 （x = 0, 0.10, 0.15, 0.20, 0.25） samples were prepared by solid state reaction method, and the sintering temperature was 1200 ℃. Electric transport property and temperature stability of magnetoresistance in La0.67 Ca0.33-x BaxMnO3 in which part Ca^2 ＋ was substituted by Ba^2 ＋ were studied through X-ray diffraction （ XRD ） patterns, scanning electron microscope （SEM） images, resistivity-temperature （p-T） curves in zero field and applied magnetic field, and magnetoresistance-temperature （MR-T） curves. The results indicated that the crystal structure changed with the variation of Ba^2＋ substitution amount, the sample with x = 0 was of cubic structure, the sample with x = 0.10 was of orthogonal structure, and the samples with x = 0.15, 0.20, 0.30 were of hexagonal structure. The electric transport property of the sample with x = 0. 10 exhibited abnormality, and its resistivity was not only 60 times as large as that of La0.67Ca0.33MnO3 without Ba doping but also several times as large as that of the samples with higher Ba doping, then the resistivity gradually decreased with the increase of Ba^2 ＋ substitution amount, and this could be explained by the lattice structure change and the distortion of MnO6 octabedron induced by Ba doping; the temperature stability of magnetoresistance near room temperature was realized in the samples with high Ba doping, magnetoresistance of the sample with x = 0.15 was （8.91 ±0. 42） % in the temperature range of 187 -246 K, that of the sample with x =0.20 was （6.07±0.32） % in the temperature range of 230 -290 K, and that of the sample with x = 0.25 was larger than 14% below 320 K and above 50 K. The temperature stability of magnetoresistance near room temperature in the magnetic field of 0.8 T was advantageous to the practical application of MR effect. The mechanism of the temperature stability of magnetoresistanee was that, the magnetoresistance of perovskite was the superposition of in- trinsic magnetoresistance induced by

关 键 词：电输运性质 磁电阻温度稳定性 钙钛矿锰氧化物 

分 类 号：O482[理学—固体物理] TM273[理学—物理]