纳米多晶La_(0．7)Sr_(0．3)MnO_(3-δ)的输运性质  

Transport properties and magnetoresistance effect of nano-polycrystalline La_(0.7)Sr_(0.3)MnO_(3-δ)

作　　者：席力[1] 刘杰[1] 田航[1] 寇晓明[1] 周雪云[1] 李成贤[1] 葛世慧[1] 

机构地区：[1]兰州大学磁学与磁性材料教育部重点实验室,甘肃兰州730000

出　　处：《兰州大学学报（自然科学版）》2008年第3期134-137,共4页Journal of Lanzhou University(Natural Sciences)

基　　金：国家自然科学基金(50371034;50701021)资助.

摘　　要：利用溶胶—凝胶法制备了纳米多晶La_(0.7)Sr_(0.3)MnO_(3-δ)(简称LSM)块体样品.详细研究了在不同烧结温度下的LSM样品电阻率随测量温度的变化关系.随着温度从室温降低,电阻率(ρ)在250 K附近存在最大值,低于该温度后,样品表现为金属导电特性,随后在50 K左右存在一极小值.通过对输运性质的研究表明在低温下(<50 K),ρ随温度降低而升高的现象与隧穿效应的理论模型(lnραT^(-1/2))符合得很好,表明这种现象是由于传导电子在通过邻近LSM晶粒间表面/界面层时的隧道效应所导致的.利用自旋回波法测量了样品中^(55)Mn的核磁共振谱图,结果表明样品中存在这种绝缘性的势垒.The resistivity of bulk polycrystalline La0.7Sr0.3MnO3-δ（LSM）, deliberately fabricated to produce nanoscale grains sintered at different temperatures, was investigated as a function of temperature. With temperature decreasing below room temperature the resistivity （ρ） exhibited a maximum near 250 K below which it displayed ＂metallic＂ behaviour, i.e. ρ∝ T^2 at 50-170 K. However, ρ subsequently exhibited a minimum near 50 K, below which it well fit the predictions for the tunneling of conduction electrons through insulating interfacial layers viz. ln ρ∝ T^-1/2, a result interpreted as conduction-electron tunneling between adjacent LSM granules. The 55^Mn zero field spin-echo nuclear magnetic resonance spectra indicated that the insulating barrier existed in LSM. The minimum of ρ occuring in these samples may have resulted from the competition of the tunneling effect and the intrinsic metallic transport mechanism of LSM.

关 键 词：多晶La0.7Sr0.3MnO3 隧道效应 核磁共振 

分 类 号：O484.4[理学—固体物理]