【摘要】 研究制备了 L a0 .6 7Ba0 .3 3Mn1 - x Fex O3(x=0 ,0 .0 5 ,0 .1)材料。结果表明 :铁替换锰降低了材料的饱和磁化强度及居里温度 ,主要是因为 Fe离子不参加双交换作用 ,同时 Mn3+ - O2 - - Mn4+ 的作用对随铁离子替代 Mn3+ 而数量减少 ,材料的铁磁作用随之减弱。铁替换锰降低了金属 -半导体转换峰温度 ,相应提高了材料的零场电阻值。值得注意的是铁掺杂提高了大磁阻材料 L a0 .6 7Ba0 .3 3Mn1 - x Fex O3的低温性能 ,5 K下磁阻比 [R(6 T) - R(0 ) ]/ R(0 )从 x=0时的- 40 %增加到 x=0 .1时的 - 6 0 %。本文同时利用迪尼模型对材料大磁阻效应进行了计算分析 ,发现理论计算曲线可以较好的反映实验上出现的金属 -半导体转换峰现象 ,同时负的大磁阻效应现象也可从理论计算上得到证实。更多还原

【Abstract】 Rare earth ceramics, La 0 67 Ba 0 33 Mn 1- x Fe x O 3( x =0,0 05,0 1), has been prepared. The saturation magnetization and Curie temperature decrease with increasing Fe content in the compounds La 0 67 Ba 0 33 Mn 1- x Fe x O 3,since Fe does not participate in double exchange interaction and the amount of bond Mn 3+ O 2 Mn 4+ decreases. The ferromagnetic interaction decreases with Fe doping in the compounds La 0 67 Ba 0 33 Mn 1 x Fe x O 3. Fe doping also dereases the transition temperature of the metal semiconductor transition peak and increases the resistance of La 0 67 Ba 0 33 Mn 1 x Fe x O 3. The colossal magneloresistance(CMR) effect at low temperatures has been improved for doped La 0 67 Ba 0 33 Mn 1 x Fe x O 3. The magnetoresistance ratio [ R (6T) R (0)]/ R (0) changes from 40% to 60% with increasing Fe content from x=0 to x=0 1 . The results also show that the metal semiconductor transition peak and the negative CMR effect are well described by the Dionne model.更多还原