【摘要】 用固相反应法制备了La2/3(CaxBa1-x)1/3MnO3(x=0.00,0.40,0.45,0.55,0.60,1.00)6种多晶CMR材料,测量了材料在77～350K范围内零磁场和0.4T外磁场下的电阻率。在不同的温度区域呈现不同的电阻率以及磁电阻随温度的变化行为,说明存在不同的磁电阻效应的机制。证实了高温下的电阻率峰为I M转变。研究发现掺杂量x=0.55,0.60两种材料在室温有较大的磁电阻,表明掺杂量大小影响材料特性。更多还原

【Abstract】 A series of polycrystal bulk samples of La_2/3(Ca_xBa_1-x)（x=0.00, 0.40, 0.45, 0.55, 0.60, 100） were prepared by standard solid reaction method. The temperature dependences of resistance and magnetoreisitance from 77 K up to 420 K were studied respectively in the surrounding of H=0 and 0.4 T. Experimental results indicate that the behaviors of ρ（or MR）-T is quite different in different temperature regions, which suggests there exist difference mechanisms of magnetoresistance effect. Based on some theory, we suggest the resistivity peak in higher temperature （near 300 K） is insulator to metal transitions. It is found that MR of the two samples (La_2/3(Ca_xBa_1-x)_1/3（x=0.55, 0.60）) is quite large, specially up to 14.5% and 19.5% respectively at room-temperature and μ₀H=1.2 T, which means doping level（x） effects properties of the materials.更多还原