【摘要】 本文采用固相反应法制备了高价态离子Mo掺杂的La0.7Ca0.2Ba0.1Mn1-xMoxO3(x=0,0.01,…,0.06)多晶样品,研究了Mo掺杂对样品的结构、磁性和磁电阻的影响.X射线衍射谱证实所有样品均为具有正交对称性的钙钛矿结构.零场冷却(ZFC)和加场冷却(FCH=0.01T)下其磁化～温度(M～T)曲线的测量表明样品随温度降低发生了从顺磁(PM)到铁磁(FM)的相变,T<Tc时样品呈现出团簇玻璃态.随Mo掺杂量的增加,样品的居里温度发生了显著变化,从x=0的294.2K降低到x=0.06的240.83K.零场和外加磁场(H=1.5T)测量得到样品的ρ～T曲线表明随温度降低(300～5K)样品的导电行为发生了从绝缘体到金属的相变,相转变温度与居里温度一样随着掺杂量的增加而明显降低(≈50K).磁阻温度曲线表明Mo掺杂提高了相变点附近的磁电阻效应,当x=0.0时,磁阻为14.11%,当x=0.06时,磁阻达到45.32%,增强了三倍多.更多还原

【Abstract】 The Mo-doping La0.7Ca0.2Ba0.1Mn1-xMoxO3(x=0,0.01,…,0.06) polycrystalline samples have been prepared by solid state reaction method. The influence of Mo-doping on the structure ,transport properties and magnetoresistance have been investigated. X-ray diffraction indicated that all of the samples have orthorhombic(Pbnm) perovskite structure. The magnetization versus temperature (M～T) curves for zero field-cooled (ZFC)and field-cooled (FC) conditions in a magnetic filed of 100 G suggest that all of the samples undergo a FM to PM phase transition. The cluster-glass state is found to be formed below Tc,meanwhile the transition temperature Tc decreases from Tc~294.2K(x=0.00) to Tc~240.83K (x=0.06) due to increasing Mo doping. The temperature dependence of resistivity ρ(T) curves are measured under H=0T and H=1.5T,which reveals a metal-insulator transition and the transition temperature TP shifts obviously to lower temperature with increasing Mo content. The temperature dependence of magnetoresistance(MR ) curve of the samples indicates that the CMR around Tp is enhanced considerably by Mo-doping. For the sample with x=0.06,MR reaches a maximum value of 45.32%,which is almost three times of the undoped sample for x=0.更多还原