多自旋态离子Co替代诱导La2/3Ca1/3MnO3体系的输运反常

利用具有多自旋态的Co离子进行Mn位替代，制备了La_2/3Ca_1/3Mn_1-xCo_xO₃ (0≤x≤0.15) 系列样品并研究了体系的结构和输运特性.结果表明，在替代范围内，样品呈现很好的单相结构，各晶格参数随替代量的增大而减小；Co替代导致体系出现电输运反常，具体表现为在居里温度T_C以下电阻-温度曲线的二次金属-绝缘转 关键词： Mn位替代 双峰现象 自旋结构 磁电阻效应

Abnormal transport behavior in the mult-spin Co-doped La2/3Ca1/3MnO3 manganites

The spin structure and polarization characters are the dominant aspects in the physical properties of manganite systems with colossal magnetoresistance effect. In this paper, a series of Mn-site doping samples La_2/3Ca_1/3Mn_1-xCo_xO₃ (0≤x≤0.15) have been prepared with Co ion which has mult-spin states. The structure and transport properties of this system have been systematically investigated. The results showed that all the samples show good single phase and the lattice parameters decrease with the increasing of doping concentration x. The abnormal transport properties are induced by Co doping. To be specific, the resistivity exhibits two metal_insulator (M—I) transitions (double peak effect). Both high temperature peak (T_MIH) and low temperature peaks (T_MIL) shift to low temperature end with increasing x. While the T_MIH shifts to high temperature, the T_MIL is almost unchanged under the external field. The corresponding peak values of resistivity show strong dependence on the external field and Co doping concentration x. All the peak values of resistivity increase with the increase of x, and the low temperature peak value seems more sensitive than the high temperature peak. Compared with the magnetization properties, it could be concluded that, the high temperature peak is related with the undoped M-I transition, and the abnormal behavior of low temperature peak has certain relationship with the oxygen vacancy and high spin state induced by Co³⁺ substituting Mn⁴⁺ in the present system.