La2/3Ca1/3MnO3/LaMnO3复合体系中颗粒间界对电磁输运行为的影响

摘要

将奈尔温度为145 K的反铁磁性绝缘体LaMnO3作为第二相复合到La2/3 Ca1/3 MnO3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)La2/3 Ca1/3MnO3/x LaMnO3复合体系中,随着x增加,样品的金属-绝缘体转变温度咒降低,峰值电阻增加.电输运行为表明:随着反铁磁性第二相LaMnO3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0.3T下,相对于纯La2/3 Ca1/3 MnO3,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3T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La2/3Ca,/3MnO3的磁电阻值.%Composites of La2/3Ca1/3MnO3/LaMnO3 were synthesized through a sol-gel method.The effects of addition of antiferromagnetic insulator LaMnO3 on electrical and magnetic properties of the composites have been investigated in detail.The structure analysis shows LaMnO3 mainly segregates at the grain boundaries of La2/3 Ca1/3 MnO3.With the increasing content of LaMnO3,the electrical transport behavior suggests that electron-phonon and electron-magnon scatterings are becoming more important.In addition,a significant enhancement in magnetoresistance (MR) under applied magnetic fields of 0.3 T and 3 T is observed over a wide temperature range,which is considered to be arising from the enhanced spin-polarized tunneling caused by the addition of LaMnO3 at the grain boundaries.