La_(5/8)Ca_(3/8)Mn_(1-x)Co_xO_3(x≤0.1)体系电阻率低温最小值现象的散射机制  

Scatting Mechanism of the Low-Temperature Resistivity Minimum in La_(5/8)Ca_(3/8)Mn_(1-x)Co_xO_3(x≤0.1) System

作　　者：程素君[1] 姚恺[1] 梁彦天[1] 

机构地区：[1]新乡学院物理系,河南新乡453000

出　　处：《河南师范大学学报（自然科学版）》2009年第3期64-67,共4页Journal of Henan Normal University(Natural Science Edition)

基　　金：河南省教育厅[教高(2005)461号]资助课题

摘　　要：主要研究了La5/8Ca3/8Mn1-xCoxO3(x≤0.1)体系的低温电输运特性.在全温区,电阻率随温度变化曲线出现双绝缘—金属转变峰现象;各样品均在25 K附近存在一个有趣的低温电阻最小值现象,外加磁场可使其向低温区移动并产生抑制作用.通过对La5/8Ca3/8Mn1-xCoxO3(x≤0.1)样品在25 K附近的电输运特性进行的拟合分析,表明存在着弹性和非弹性散射过程的竞争,可用库仑相互作用和非弹性电子散射解释.拟合参数值的变化表明来自电子—电子、电子—声子及电子—磁子散射的共同作用,且电子—电子相互作用随着Co掺杂量的增加而增强,这与样品在低温下存在的铁磁—反铁磁相互竞争产生的团簇玻璃态有关.随着Co掺杂量增大,FM团簇减少且自旋冻结,使载流子局域化增强而导致电阻率增大.证明了与磁场和温度有关的电子散射进程引起电子的局域化效应乃是导致体系输运行为发生变化的主要原因.This paper has studied the scatting mechanism of the low-temperature resistivity minimum in La5/8Ca3/8Mn1-xCoxO3（x≤0.1）. The double peaks phenomenon is oecured in temperature dependence of the resistivity. The doping can suppress the conductivity of the system, but it favors the large CMR effect. The electron localization arises mainly from strongly temperature and field dependence of electron scattering process and it is a main contribution to the conductivity in the whole temperature range. The results obtained for the resistivity at zero applied magnetic field exhibit a shallow minimum at the temperature T-25 K which shifts towards lower temperatures upon applying a magnetic field. It can fit the experience formula （ρ=ρ-BT^1/2＋CT^n）, and explained with Coulomb interaction （CI） and the electric scatting process. It is proved that there exists the electron localization effect induced by Co doping, caused by enhanced electric scatting process related to magnetic field and temperature. It is the main reason why the transport properties of system changes.

关 键 词：La5/8Ca3/8Mn1-xCoxO3(x≤0.1)体系 电阻率低温最小值 散射机制 

分 类 号：O513[理学—低温物理]