纳米La_(0.67)Sr_(0.33)MnO_3块体的磁性与电输运特性研究

采用溶胶–凝胶法制备了纳米La0.67Sr0.33MnO3样品,通过XRD、TEM及PPMS(物理性质测量系统)研究了样品的结构、磁性和电输运特性。结果表明,样品为单相菱方钙钛矿结构,平均晶粒大小为61 nm,在10 K到300 K间样品具有铁磁性和绝缘体导电行为,在温度小于60 K时因库仑阻塞效应样品电阻随温度降低急遽增加。纳米晶粒尺寸导致样品具有强的磁电阻效应,其中低场磁电阻效应由晶粒间自旋极化电子隧穿界面引起,高场磁电阻效应由界面磁无序引起。

Study of magnetic and electrical transport properties in La0.67Sr0.33MnO3 nano-compacts

Nano-powder La0.67Sr0.33MnO3 was synthesized using the sol-gel method.The structure,magnetic and electrical transport properties were studied through XRD,TEM and PPMS measurements.The results indicate that the prepared sample is of single phase with rhombohedral perovskite structure and an average grain size of 61 nm.The sample presents ferromagnetism and insulator-like transport behaviors from 10 K to 300 K.The observed fast upturn in the low-temperature resistance is understood in terms of the Coulomb blockade effect.The small grain size results in the strengthened magnetoresistance,including the low field magnetoresistance due to spin polarized tunneling and the high field magnetoresistance induced by the spin disorder in grain boundaries.