层状结构锰氧化物La_(2-2x)Sr_(1+2x)Mn_2O_7的EXAFS研究  

Study on the layered perovskite manganites La_(2-2x)Sr_(1+2x)Mn_2O_7 by EXAFS

作　　者：王爱华[1,2] 刘洋[1] 曹国辉[1] 马颖[1] 刘涛[3] 张静[3] 谢亚宁[3] 李风英[4] 

机构地区：[1]北京科技大学材料物理与化学系 [2]首都师范大学物理系,北京100037 [3]中国科学院高能物理所同步辐射实验室 [4]中国科学院物理所高压组

出　　处：《功能材料与器件学报》2004年第3期313-317,共5页Journal of Functional Materials and Devices

基　　金：北京市自然科学基金资助项目(No.2022013)

摘　　要：采用溶胶-凝胶法和传统的固相反应法相结合,制备了双层钙钛矿结构锰氧化物La2-2xSr1+2xMn207较宽掺杂范围内(0.2≤x≤0.6)系列单相样品,并测量了各样品的X射线衍射谱(XRD)和扩展X射线吸收精细结构(EXAFS)谱。通过对XRD的分析证实样品均为Sr3Ti2O7型四方结构,空间群为I4/mmm,同时发现晶格参数a随掺杂量x的变化几乎不变,而c随x的增加则明显减小。通过对EXAFS的分析和研究得到MnO6八面体中c轴方向的Mn-O键长和Jahn-Teller畸变量ΔJT随掺杂浓度x的变化,发现在最佳掺杂浓度x=0.33附近,J-T畸变最大,显示出La2-2xSr1+2xMn207(0.2≤x≤0.6)系列锰氧化物的磁电性能与畸变量ΔJT密切相关。Double layered perovskite manganites La2-2xSr1+2xMn2O7 (0.2≤x≤0.6) were synthesized by sol-gel method and conventional solid state reaction method. X-ray powder diffraction was tested to characterize the crystal of the samples. The analyses indicate that the crystals are single-phase with I4/mmm tetragonal lattice symmetry. As the strontium concentration increases, the parameter a prac-tically does not change, whereas the parameter c decreases. Extend X-ray absorption fine structure (EXAFS) measurements at the Mn K-edge as a function of doping level x were performed on La2-2xSr1+2xMn2O7. All samples have a Jahn-Teller (J-T) distortion, further more, the J-T distor- tion magnitude ΔJT gets the biggest value at x=0.33. Simultaneously the Debye-Waller factor σ2 for the Mn-O(1) and Mn-O(2) atom pairs vs x are similar to ΔJT. These results suggest that the mag- netism-electricity of layered perovskite manganites La2-2xSr1+2xMn2O7 is closely related with the ΔJT.

关 键 词：层状结构 锰氧化物 La2-2xSr1+2xMn2O7 EXAFS 溶胶-凝胶 LSMO 

分 类 号：O614.711[理学—无机化学]