逾渗驱动的高自旋极化氧化物材料磁电阻增强效应——网络效应与调控  

PERCOLATION-INDUCED ENHANCEMENT OF MAGNETORESISTANCE EFFECT IN HIGN SPIN-POLARIZED OXIDES:NETWORK EFFECTS

作　　者：蔡田怡[1] 雎胜[1] 孙华[1] 李振亚[1] 

机构地区：[1]苏州大学物理科学与技术学院江苏省薄膜材料重点实验室,苏州215006

出　　处：《物理学进展》2008年第1期50-71,共22页Progress In Physics

基　　金：国家自然科学基金项目(10474069;10504023;10404018)

摘　　要：锰氧化物具有内禀的多尺度非均匀性,这与同时活跃的多个自由度——自旋、电荷、晶格和轨道——非线性耦合,以及多种相互作用的共存密切相关。更重要的是,这种极为特殊的物理现象可能是庞磁电阻效应的微观起源——铁磁金属相在磁场作用下的逾渗而驱动的磁电阻效应。另一方面,在某组分导电逾渗阈值附近的磁电阻显著增强效应,是高自旋极化氧化物颗粒体系所具有的普遍现象之一。因此,针对各种高自旋极化氧化物的非均匀和颗粒复合体系,逾渗驱动磁电阻增强效应的研究具有重要的学术意义和应用价值,其中输运网络理论为重要的理论研究。在充分认识电磁输运微观机制的基础之上,通过调控输运网络的结构,探讨逾渗驱动磁电阻增强的必要条件,可以找出实现可控性高且幅值较大的磁电阻的新途径、新方法。本文主要基于电阻网络模型,综述高自旋极化氧化物材料中多相共存体系的磁输运性质研究的主要背景和发展现状,充分结合相关的实验结果,介绍逾渗驱动磁电阻效应增强的物理机制,以及各类电输运网络的构建,并展望未来的发展。A wide variety of experimental results and theoretical investigations have convincingly demonstrated that manganese oxides are spatially inhomogeneous, due to the several simultaneously active physical degrees and coexisted exchange interactions. Colossal magnetoresistance is closely related to the inhomogeneity, which is a result of the percolative metallic component induced by magnetic field. On the other hand, as a kind of network effects, the enhancement of magnetoresistance is ubiquitous in the com- posites. To explain these phenomena, studying the properties of magnetotransport network is important. Based on resistor network model, we review the background and recent research results of the magneto- transport properties in phase separated/coexisted high spin-polarized oxides, search the ways to obtain the enhanced magnetoresistance, study the construction of resistor network, explain the experimental results, and discuss the future developments in this field.

关 键 词：自旋极化 磁电阻 网络效应 半金属 逾渗 

分 类 号：O482.5[理学—固体物理]