中文摘要：

运用X射线衍射（XRD）分析技术,对钙钛矿型La0.55Ca0.45MnO3化合物的空间结构进行了变温测量,用Rietveld方法对XRD实验数据进行了精修拟合.随着温度的降低,实验上观测到衍射峰的劈裂,暗示该化合物内部晶体结构发生了相变.磁化曲线测量表明,对应晶体结构相变的温度,化合物的磁性也发生由铁磁性向反铁磁性的转变.运用Rietica软件对化合物的XRD数据进行了处理,得到了La0.55Ca0.45MnO3晶体内的电子密度分布图.结果显示,结构相变前后的电子密度分布图之间存在着巨大的差异.结合样品的晶胞参数随温度的变化和Jahn-Teller效应不同畸变模式,对电子密度分布的巨大变化给出了定性的解释.

英文摘要：

The temperature-dependent spatial structure of perovskite oxide La0.55 Ca0.45 MnO3 has been checked by X-ray diffraction（XRD） and Rietveld method was employed to refine the XRD data.It was found that with the decrease of temperature,almost all of the diffraction peaks were split;each peak was divided from single peak at high temperature into two peaks at low temperature,indicating the appearance of a crystalline structural phase transition.Corresponding to the structural phase transition,magnetization measurements also revealed a magnetic transition from ferromagnetism to antiferromagnetism.With the Rietica analysis of the XRD data of the compound,plots of the electronic density distribution of La0.55Ca0.45MnO3 were made.Sharp difference in the distributions above and below the transition temperature was clearly shown.Taking the magnetism of the compound into consideration,the structural phase transition was analyzed and the sharp difference of the electronic density distribution was qualitatively explained.