Transactions of Nonferrous Metals Society of China The Chinese Journal of Nonferrous Metals

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中国有色金属学报

ZHONGGUO YOUSEJINSHU XUEBAO

第15卷    第12期    总第81期    2005年12月

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文章编号: 1004-0609(2005)12-1968-06
稀土空位锰氧化物(La(1-x-y)Yy)2/3Ca1/3MnO3
结构和输运性质
罗广圣1, 2, 3, 李小怡2, 3, 吴小山2, 3

(1. 华中科技大学 材料科学与工程学院, 武汉 430074;
2. 南昌大学 材料科学与工程学院, 南昌 330047;
3. 南京大学 固体微结构国家重点实验室, 南京 210093
)

摘 要:  用固相反应法制备了La(1-x)2/3Ca1/3MnO3(V-LCMO)和
(La(0.7-x)Y0.3)2/3Ca1/3MnO3)(V-LYCMO)(x=0, 0.02, 0.04, 0.08, 0.10)系列La空位锰氧化物样品。 X射线衍射(XRD)分析表明: 所有的样品均为单相, 具有正交对称性(Pnma)。 La(1-x)2/3Ca1/3MnO3系统和(La(0.7-x)Y0.3)2/3Ca1/3MnO3系统的晶格参数以及Mn—O键长和Mn—O—Mn键角随La空位浓度不同而改变,说明在室温系统中存在Jahn-Teller效应。 对于V-LYCMO系统,其晶格参数、 Mn—O键长和Mn—O—Mn键角都比V-LCMO相应的值更小, 这可能与离子半径小的Y3+部分替代La3+导致更大的晶格畸变有关。 V-LCMO系统随着空位浓度的增大,绝缘体-金属的转变温度TMI几乎不变。 在x=0.04时MR值在温度TMI处达到最大值, 约为220%(8T)。 而对V-LYCMO系统, 其转变温度TMI约为50 K, 在温度40~50 K左右最大的磁电阻值超过106%。认为很大的磁电阻效应与用离子半径小的Y部分替代离子半径大的La有关,它会破坏双交换作用, 从而导致Jahn-Teller效应。

 

关键字:  La(1-x)2/3Ca1/3MnO3; (La(0.7-x)Y0.3)2/3Ca1/3MnO3; La空位; 正交对称; Jahn-Teller效应

Structural and transport properties of
manganese oxides (La(1-x-y)Yy)2/3Ca1/3MnO3
with rare earth vacanties
LUO Guang-sheng1, 2, 3, LI Xiao-yi2, 3, WU Xiao-shan2, 3

1. School of Materials Science and Engineering,
Huazhong University of Science and Technology, Wuhan 430074, China;
2. School of Materials Science and Engineering,
Nanchang University, Nanchang 330047, China;
3. State Key Laboratory of Solid Microstructures,
Nanjing University, Nanjing 210093, China

Abstract: Some La-vacancy samples of manganese oxides La(1-x)2/3Ca1/3MnO3 and (La(0.7-x)Y0.3)2/3Ca1/3MnO3(x=0, 0.02, 0.04, 0.08, 0.10) were prepared by solid-state reaction method. All the samples are single phase, with orthorhombic symmetry(Pnma), analyzed by XRD. The lattice parameters, Mn—O bond length and Mn—O—Mn bond angle of both systems vary with different La-vacancy concentration, which indicates there exists Jahn-Teller effect in the system. For V-LYCMO system, its lattice parameters, Mn—O bond length and Mn—O—Mn bond angle are smaller than those of V-LCMO system, which may be related to the bigger lattice distortion. For V-LCMO system, a metal-insulator transition is observed at about -267 K. The maximum of the magnetoresistance value is about 220% at TMI when x is 0.04. For V-LYMCO system, TMI is observed at about 50 K, a very larger magnetoresistance up to about 106% is observed at 40-50 K. It is suggested that it may be related to the partial substitution of La3+ cation with smaller Y3+, which may destroy the double exchange interaction of Mn—O—Mn, giving rise to Jahn-Teller effect.

 

Key words: La(1-x)2/3Ca1/3MnO3; (La(0.7-x)Y0.3)2/3Ca1/3MnO3; La-vacancy; orthorhombic symmetry; Jahn-Teller effect

ISSN 1004-0609
CN 43-1238/TG
CODEN: ZYJXFK

ISSN 1003-6326
CN 43-1239/TG
CODEN: TNMCEW

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