Pr替代La_(5/8)Ca_(3/8)MnO_3体系的磁性与电输运特性

Electrical Transport and Magnetic Properties of Pr-doping La_(5/8)Ca_(3/8)MnO_3 Perovsksite Manganese

系统地研究了多晶La5/8-xPrxCa3/8MnO3(x=0,0.10,0.13,0.15)体系的磁性和电输运特性,并报道了这一体系的电阻率极小值行为.X射线粉末衍射测量表明,所有的样品都具有较好的单相结构;电输运和磁性测量结果表明,随掺杂量的增大,居里温度Tc和绝缘体-金属转变温度TMI都向低温区移动.在较低温度下电阻率表现出了极小值现象,而这一现象随外加磁场的增大逐渐受到抑制,对此现象从强电子-电子相互作用角度进行了分析讨论.在Tc和TMI转变温.度区域,样品表现出较大的磁电阻效应.样品在高温下的电输运行为可根据可变程跃迁机制得到很好的解释.

In this paper, electrical transport and magnetic properties of polycrystalline La5/8-x Prx Ca3/8 MnO3 （x =0, 0.10, 0.13, 0.15） are investigated systematically. Low temperature resistivity minima for La5/8-x Prx Ca3/8MnO3 systems are reported. X-ray powder diffraction measurement shows that all prepared samples have good single phases. Magnetic and electrical transport measurements indicate that both Curie point Tc and the metal-insulator transition TMI shift to lower temperature with the increasing doping of Pr compositions, while the behavior of resistivity minima appears at low-temperature for all samples. Resistivity minima are depressed gradually with the increasing magnitude of applied magnetic field. This phenomenon is analyzed according to the enhanced electron-electron interactions. Meanwhile, a larger magneto-resistance （MR） arises in the region of transition temperature of TMI and Tc Electrical transport properties at higher temperature can be explained quite well based on the variable-range-hopping （VRH） theory.