稀土材料La—Ba—（Mn,Fe）—O的磁电输运特性探讨

研究制备了Ｌａ０．６７Ｂａ０．３３Ｍｎ１－ｘＦｅｘＯ３（ｘ＝０，０．０５，０．１）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Ｍｎ＾３＋－Ｏ＾３－Ｍｎ＾４＋的作用对随铁离子替代Ｍｎ＾３＋而数量减少，材料的铁磁作用随之减弱。铁替换降低了金属－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Ｌａ０．６７Ｂａ０．３３Ｍｎ１－ｘＦｅｘＯ３的低温性能，５Ｋ下磁阻比「Ｒ（６Ｔ）－Ｒ（０）」Ｒ（０）从ｘ＝０时的－４０％增加到ｘ＝０．１时的－６０％。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。

Investigation of Magneto-Electronic Transport Behavior in La-Ba-(Mn,Fe)-O Ceramics

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.