利用固相反应法制备了Ru掺杂La0．7Ca0．2Ba0．1Mn1-xRuxO3（x=0～0．06）的多晶样品，探讨了Ru掺杂对体系结构，输运性质以及磁电阻的影响．多晶X射线衍射证实所有样品均保持简单立方钙钛矿结构．通过零场冷却（ZFC）和加场冷却（FC）下的磁化曲线的测量发现随温度降低样品发生了顺磁（PM）到铁磁（FM）的相变，且样品的居里温度（Tc）随Ru掺杂发生了显著的变化，从x=0．00时的306．7K，下降到x=0．02时的294．3K，紧接着又上升到x=0．04时的302．4K．测得居里温度明显高于La0．7Ca0．2Ba0．1Mn1-xRuxO3体系，而且其磁性也大为增强．由零场和外加磁场H=1T测量得到样品的p～T曲线表明随温度降低样品同时发生了从绝缘体到金属的转变，绝缘体-金属转变温度低于相应的居里温度．适量的Ru掺杂降低了样品的电阻率，增强了低温时的磁电阻．
The Ru-doping La0.7Ca0.2Ba0.1Mn1-xRuxO3 （x = 0- 0. 06 ） polycrystalline samples have been prepared by solid state reaction method. The influence of Ru-doping on the structure , transport properties and magnetoresistance have been investigated. X-ray diffraction indicated that all the samples are of simple cubic perovskite structure. The magnetization versus temperature （M- T） curves for zero field-cooled （ZFC）and field-cooled （F C） conditions in a magnetic filed of 1000G suggest that all of the samples undergo a ferromagnetic （FM） to paramagnetic （PM） phase transition. The Curie temperature Tc are found to go through a striking change upon Ru doping, which decreases from 306.7K（x=0. 00） to 294. 3K（x=0. 02）, but reaches 302. 4K for x=0. 04. Obviously, Tc is higher than that of La0.7Ca0.2Ba0.1Mn1-xRuxO3, and the magnetism is enhanced obviously. The temperature dependence of resistivity p（T） curves are measured under H=0T and H=IT, which reveals a metal-insulator transition and the transition temperature TIM is much lower than the corresponding Curie temperature To. Moderate Ru doping thus can reduce the resistivity of the samples, and meanwhile enhance the magneteresistence of the samples at low temperature.
参考文献
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