【摘要】 研究了Al和Fe替代的La0 .6 7Ca0 .33Mn1-xMxO3体系的结构特征及其对金属 绝缘转变的影响 .结果表明 ,随Fe替代含量的增加 ,晶胞体积并未有显著的变化 ;而随Al替代含量的增加 ,在整个替代范围内 ,晶胞体积表现为单调减小 .两种替代均使体系的电阻率急剧增加 ,绝缘 金属转变温度TIM向低温方向移动 .对少量替代含量 ,在T <TIM的低温区域满足金属输运行为 ,这种输运行为随Al和Fe离子替代含量的变化特征 ,可从Al3+离子和Fe3+离子对Mn3+ O2 - Mn4 +双交换通道的破坏给予解释 .对于较高的替代含量 ,Al离子的替代除通过形成Al3+ O2 - Mn4 +作用通道影响双交换外 ,由晶格畸变所导致的电声子耦合变化也会影响双交换 ,而对于Fe离子的替代 ,由于反铁磁簇的存在所诱发的Mn离子自旋对电子的散射可能是影响体系输运特性的重要原因 .更多还原

【Abstract】 The influence of Al\+ 3+ and Fe\+ 3+ doping on structure and metal insulator ( M I ) transition behavior of the colossal magnetoresistance material La\- 0.67 Ca\- 0.33 MnO\-3 has been studied systematically. It is found that the cell volume is almost independent of the Fe\+ 3+ doping content, but it decreases monotonously with the Al\+ 3+ doping content. In these two systems, the resistance increases rapidly and the M I transition temperature shifts to lower temperature region with increasing the doping content. If the doping content is quite small, the transport properties of the samples manifest metallic characteristics in the temperature range of T<T \- IM , which may be attributed to the blocking effect of the double exchange channel of Mn\+ 3+ O\+ 2- Mn\+ 4+ caused by Al\+ 3+ and Fe\+ 3+ ions. If the doping content is comparable high, however, both the Al\+ 3+ O\+ 2- Mn\+ 4+ channel and electro phonon coupling induced by crystal lattice distortion could influence the double exchange seriously in Al\+ 3+ doping system, while the electron scattering by the spins of Mn ions induced by antiferromagnetic clusters may be mainly responsible for the double exchange in Fe\+ 3+ doping system.更多还原