SrTiO_3掺杂La-K-Mn-O系统的电磁性质  

Magnetic and electronic transport properties of SrTiO_3-doped La-K-Mn-O system

作　　者：吴坚[1] )张世远[2] 

机构地区：[1]河海大学理学院,南京210098 [2]南京大学物理系,南京210093

出　　处：《物理学报》2007年第2期1127-1134,共8页Acta Physica Sinica

基　　金：河海大学校基金(批准号:2013/406083;1014/405139)资助的课题~~

摘　　要：用溶胶-凝胶制备了La0.833K0.167MnO3-SrTiO3(LKMO/STO)系列样品,并研究了它们的结构、磁性和输运特性.X射线衍射实验表明,1200℃烧结的LKMO/STO(STLK12)是一个均匀的固溶相.其电阻率表现为绝缘体的行为,而纯La0.833K0.167MnO3(LKMO)样品随温度的升高则有金属-绝缘体转变.在低场下(μ0H=0.02T),对STLK12样品,当温度从220K降低到4K时,磁电阻从0.2%升高到11%.在高场下(μ0H=5.5T),随着温度降低,磁电阻几乎是线性增大.在4.2K时,达到65%.比纯LKMO样品40%的磁电阻高出了25%.我们用晶界处的自旋极化隧穿效应定性地解释了这种增强的磁电阻效应.La0.833 K0.167 MnO3 （LKMO） and La0.833 K0.167 MnO3/SrTiO3 （LKMO/STO） are fabricated at different temperatures. STLK08, STLK10 and STLK12 stand for the samples sintered at 800, 1000 and 1200℃ respectively. X-ray diffraction （XRD） shows that all of the three samples consisted of homogeneous solid solution phases. The resistivity for LKMO shows insulator-metal transition with decreasing temperature, but the resistivities of STLK10 and STLK12 show an insulator behavior over the whole temperature regime （4-300 K）. The low-field （0.02 T） magnetoresistance increases from 0.2% to 11% with temperature decreases from 250 K to 4 K for STLX12 sample. The high field （μ0H = 5.5 T） magnetoresistanee almost increases linearly with decreasing temperature, which is much higher than the magnetoresistance of LKMO （The high field magnetoresistance are 65% and 40% at 4 K for STLK12 and LKMO, respectively）. The enhancement in magnetoresistance is quantitatively explained by spin-polarizedtunneling at grain boundaries.

关 键 词：低场磁电阻 高场磁电阻 白旋极化隧穿 钙钛矿 

分 类 号：O482.5[理学—固体物理]