颗粒表面覆Cu的La2/3Ca1/3MnO3复合颗粒系统中的低场高磁电阻效应

用化学方法将Cu有关的材料引入到La2／3Ca1／3MnO3颗粒表面以形成复合颗粒系统．低磁场(0．3T)下磁电阻与温度关系测量表明，伴随着Cu有关材料的引入，磁电阻图像发生了明显变化．对纯La2／3Cal／3MnO3颗粒系统，磁电阻随温度降低而单调增加；而对复合颗粒系统，磁电阻最明显的特征是绝缘体-金属转变温度附近表现出尖的磁电阻峰，且有较高的磁电阻值．结合低场磁化实验对实验结果进行了讨论．

Large Magnetoresistance under a Low Applied Magnetic Field in a Cu-dependent Material Coated-La2/3Ca1/3MnO3 Granular System

A composite granular system consisting of La2/3Ca1/3MnO3 grains and Cu-dependent material, introduced into the boundary region of the granular surface, was fabricated in a chemical route. The measurement of magnetoresistance versus temperature dependence for a low magnetic field (0.3 T) indicates that the features of magnetoresistance in the composite granular system are significantly different from that in pure La2/3Ca1/3MnO3. The pure La2/3Ca1/3MnO3 granular system shows a monotonic increasing response in magnetoresistance with cooling. But for the composite granular system, a sharp peak with large magnetoresistance appears in the magnetoresistance versus temperature curve at a temperature near which the insulator-metal transition occurs. The experimental observation was discussed based on the measurement of low-field magnetization.