La_(0.5)Sm_(0.2)Sr_(0.3)MnO_3/Ag_x中的室温磁电阻增强  

ENHANCEMENT OF ROOM-TEMPERATURE MAGNETORESISTANCE IN La_(0.5)Sm_(0.2)Sr_(0.3)MnO_3/Ag_x

作　　者：王桂英[1] 彭振生[1,2] 唐永刚[1] 刘鹏[1] 牛晓飞[1] 

机构地区：[1]宿州学院自旋电子与纳米材料安徽省重点实验室,安徽宿州234000 [2]中国科学技术大学结构分析重点实验室,合肥230026

出　　处：《低温物理学报》2009年第3期188-192,共5页Low Temperature Physical Letters

基　　金：国家自然科学基金重点项目(19934003);安徽省教育厅自然科学研究重大项目(ZD2007003-1);安徽省高等学校自然科学研究项目(KJ2008A19ZC);宿州学院教授(博士)科研启动基金项目(2006jb02)资助的课题~~

摘　　要：用固相反应法制备La0.5Sm0.2Sr0.3MnO3/(Ag2O)x/2(x=0.00,0.04,0.08,0.25,0.30)样品,通过M～T曲线,ρ～T曲线,ρ～T拟合曲线,研究样品的磁性质、输运行为、输运机制及磁电阻效应.结果表明:少量掺杂时Ag可能参与反应.掺杂量较多时,Ag主要以金属态分离到母体颗粒的界面处,使体系形成两相复合体.少量的Ag掺杂可以明显提高自旋相关散射产生的晶界磁电阻.掺Ag为30%摩尔比时,样品的电阻率较低掺杂样品的电阻率降低一个数量级,在300K、0.5T磁场下,磁电阻明显增强,达到9.4%,这与颗粒母体界面结构的改善有关,也与材料电阻率的降低有关.La0.5Sm0.2Sr0.3MnO3/（Ag2O）x/2（x=0.00,0.04,0.08,0.25,0.30）samples were prepared by the solid- state reaction method, and their magnetic proverties , transport behavior, transport mechanism and magnetoresistance effect were studied through M-T curves measuring ,ρ-Tcurves measuring and fitting. The results showed that： Ag may take part in reaction when the doping amount is small. Ag is mainly distributed at the grain boundary of the mother body and is in metallic state when the doping amount is relatively large, then the system becomes a two-phase composite. A small a- mount of Ag doping can apparently increase grain-boundary magnetoresistance induced by spin-dependent scattering. The resistivity of the sample doped with 30tool. % Ag is one order of magnitude smaller than that of low-doped samples, and its magnetoresistanee in the magaetic field of 0.5T and at 300K strengthens apparently and reach 9.4%, which is connected not only with the improvement of grain-boundary structure of the mother body but also with the decrease of material resistivity.

关 键 词：室温低场磁电阻 晶界磁电阻 二相复合体 钙钛矿锰氧化物 

分 类 号：O482.5[理学—固体物理]