La_(2/3)Ca_(1/3)MnO_3/LaMnO_3复合体系中颗粒间界对电磁输运行为的影响  

Effects of grain boundaries on electrical,magnetic and magnetoresistance properties of La_(2/3)Ca_(1/3)MnO_3/LaMnO_3 composites

作　　者：李派[1] 苗良爽 张清风[1] 何云斌[1] 

机构地区：[1]湖北大学材料科学与工程学院,湖北武汉430062

出　　处：《湖北大学学报（自然科学版）》2017年第3期231-235,共5页Journal of Hubei University：Natural Science

基　　金：国家自然科学基金(51572073;61274010;51602093);湖北省自然科学基金(2015CFA038;2015CFB265;2016AAA031)资助

摘　　要：将奈尔温度为145 K的反铁磁性绝缘体LaMnO_3作为第二相复合到La_(2/3)Ca_(1/3)MnO_3颗粒间界处,研究反铁磁性绝缘体对复合体系的电磁输运性质的影响.在(1-x)La_(2/3)Ca_(1/3)MnO_3/xLaMnO_3复合体系中,随着x增加,样品的金属-绝缘体转变温度Tp降低,峰值电阻增加.电输运行为表明:随着反铁磁性第二相LaMnO_3的引入,电子-声子散射以及电子-磁振子散射对输运行为的影响变大.在低磁场0.3 T下,相对于纯La_(2/3)Ca_(1/3)MnO_3,复合样品在金属-绝缘体转变温区附近的磁电阻大大增强;在高场3 T下,所有样品都存在着磁电阻平台现象,且复合样品的磁电阻值在低温区域都明显大于纯La_(2/3)Ca_(1/3)MnO_3的磁电阻值.Composites of La_(2/3)Ca_(1/3)MnO_3/LaMnO_3 were synthesized through a sol-gel method.The effectsof addition of antiferromagnetic insulator LaMnO_3 on electrical and magnetic properties of the composites havebeen investigated in detail.The structure analysis shows LaMnO_3 mainly segregates at the grain boundaries of La_(2/3)Ca_(1/3)MnO_3.With the increasing content of LaMnO_3,the electrical transport behavior suggests thatelectron-phonon and electron-magnon scatterings are becoming more important.In addition,a significantenhancement in magnetoresistance(MR) under applied magnetic fields of 0.3 T and 3 T is observed over awide temperature range,which is considered to be arising from the enhanced spin-polarized tunneling causedby the addition of LaMnO_3 at the grain boundaries.

关 键 词：LA2/3CA1/3MNO3 复合体系 颗粒间界 超大磁电阻 磁输运行为 

分 类 号：O611.6[理学—无机化学]