La_(0.7-x)Ce_xCa_(0.3)MnO_3低场磁电阻的晶格效应  

LATTICE EFFECTS ON LOW FIELDS MAGNETORESISTANCE IN POLYCRYSTALLINE La_(0.7-x)Ce_xCa_(0.3)MnO_3

作　　者：李燕飞[1] 张光宇[1] 桂太龙[1] 王义杰[1] 宋威[1] 

机构地区：[1]哈尔滨理工大学应用科学学院,哈尔滨150080

出　　处：《低温物理学报》2004年第2期126-130,共5页Low Temperature Physical Letters

基　　金：国家自然科学基金 (批准号 :90 2 0 70 14 );黑龙江省自然科学基金资助项目 (批准号 :F0 1 2 1)~~

摘　　要：以稀土元素铈部分替换钙钛矿结构亚锰酸盐中的镧 ,使A位离子半径 <rA>减小 .由此在晶格中产生的内压将影响到B位d轨道与O位p轨道之间交叠形成的电子活性能带 .本文以固相反应法制备了多晶La0 .7-xCexCa0 .3MnO3样品 (x =0 ,0 .0 5 ,0 .10 ,0 .2 0 ) ,测量并研究了电阻、低场磁电阻与温度 (77K～ 30 0K)之关系 .实验表明 ,随Ce替代量的增加 ,磁电阻(MR)峰值无显著变化 ,而MR峰值出现的温度Tp 则递减 .关于“ <rA>减小可能导致Mn O Mn键角减小而最终使Tc 降低”The manganite polycrystalline samples La-{0.7-x}Ce-xCa-{0.3}MnO-3 (x=0, 0.05, 0.10, 0.20) were prepared by the solid-state reaction technique. The electrical resistance (R) and low fields magnetoresistance (MR) have been measured in the temperature region from 77K to 300K in applied fields from zero to 0.25 Tesla. The element substitution of Ce for La and the doping concentration dependence of R and MR were studied. It is found that the giant magnetoresistance (GMR) in the Ce doping samples does not change obviously, while the characteristic temperature T-P, at which the peak of MR appears, descend from that in La-{0.7}Ca-{0.3}MnO-3. The notion that decreasing <r-A> results decrease in the Mn-O-Mn bond angle as well as T-c avail to understand these experimental results.

关 键 词：磁电阻 亚锰酸盐 晶格效应 钙钛矿结构 电子活性能带 固相反应法 

分 类 号：O441[理学—电磁学]