用溶胶-凝胶（so-lgel）法制备了多铁Bi1-xLaxMnO3（BLMO,0.1≤x≤0.4）系列样品.样品的结构表征（X-射线衍射,扫描电子显微镜）及差热-热重（TG-DTA）分析测量显示,形成稳定的BLMO钙钛矿相的烧结温度位于900-950℃.La掺杂对BLMO样品（950℃烧结）的结构和磁性能的影响也被仔细研究.结果显示,随着La掺杂减少,样品中BLMO钙钛矿相减弱,铁磁转变温度（TC）由53K降至41K,而饱和磁化强度经历了先降低再升高的变化.这可归因于La含量较少的样品中Bi空位浓度的增加诱导了Mn-O-Mn键角的减小和局域Mn4＋离子的增多,使得Mn3＋和Mn4＋离子的铁磁超交换增强和Mn3＋离子的dz2轨道有序受到局域破坏.
Multiferroic Bi1-xLaxMnO3（BLMO,0.1（x≤0.4） samples were synthesized by the sol-gel method.The structure of BLMO samples were characterized by using X-ray diffraction（XRD）,scanning electronic microscope（SEM）,and the thermo gravimetric analysis-differential thermal analyses（TG-DTA）.It was shown that the BLMO sample with a stable perovskite phase was sintered at temperature of 900-950℃.It was also carefully investigated that the La doping effect on the structural and magnetic properties of the BLMO samples sintered at 950℃.Our results indicated that the perovskite phase of samples was weakened as La doping reducing,the Curie temperature TC decrease from 53K to 41K,corresponding to the saturation magnetization experienced a lowering and then an enhancing.It was ascribed to the increase of Bi vacancies in La doping reducing samples,which induced a decrease of Mn-O-Mn bond angle and an increase of Mn4＋ ions.This resulted in an enhancing of the ferromagnetic superexchange between Mn3＋ and Mn4＋ ions and a disrupting of the dz2 orbital ordering around the Mn3＋ matrix.
参考文献
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