摘要
用固相反应法制备La(1-x)2／3Ca1／3MnO(V-LCMO)和(La(0.7-x)Y0.3)2／3Ca1／3MnO3)(V-LY- CMO)(x<0．15)系列的La空位锰氧化物样品。X射线衍射(XRD)测量分析表明所有的样品均为单 相,具有正交对称性(Pnma)。体系的晶构参数以及Mn-O键长和Mn-O-Mn键角随空位浓度不 同而改变,表明局域Jahn-Teller效应的存在。输运测量表明,不同的空位及空位浓度影响磁电阻 效应,在x=0．04时磁电阻值在转变温度TMI处达到最大值约为220％,我们认为很大的磁电阻效应 与Y部分替代La有关,是双交换作用与Jahn-Teller效应竞争的结果。
Some La-vacancy samples of manganese oxides La（1-x）2/3Ca1/3MnO3（V-LCMO）and （La（0.7-x）Y0.3）2/3Ca1/3MnO3）（V-LY-CMO）（x〈0.15） have been prepared by solid - state reaction method. All the samples are single phase, with orthorhombic symmetry （Pnma） ,analyzed by XRD with Rietveld Refinement.The lattice parameters,Mn- O bond length and Mn - O Mn bond angle of La2/3Ca1/3MnO3 system and （La（0.7-x）Y0.3）2/3Ca1/3MnO3） system vary with the different La- vacancy concentration, which indicates the system exists Jahn -Teller effect. The maximum of the magnetoresistance value is -220 % at about TIM 268K at vacancy concentration x = 0.04. For V - LYMCO system, there is metal - insulator transition observed at about T = 50K. A very larger magnetoresistance up to about 106 % is observed at the temperature of about 40-50K. We argue the very large magnetoresistance effect may relate to the partial substitution of La^3＋ cation with smaller Y^3＋ , which may destroy the double exchange interaction of Mn - O - Mn, giving rize to Jahn - Teller effect.
出处
《常熟理工学院学报》
2005年第6期9-13,共5页
Journal of Changshu Institute of Technology
基金
国家自然科学基金资助项目(10474031
90201039)高等学校博士学科点专项科研基金资助课题(20020284029)
