Anomalous Structural Change of Layered Perovskite Manganites La2-2x Sr1+2xMn2O7
Aihua Wang1, 2, Tao Liu3, Yang Liu4, Guohui Cao1, 4, Cheng Dong5, Ning Chen1, 4, Zhaosheng Feng 6, Yang Li*, 7
1 Department of Physics, Beijing University of Science and Technology, Beijing 100083, China
2 Department of Physics, Capital Normal University, Beijing 100037, China
3 Beijing Synchrotron Radiation Laboratory, Institute of High Energy Physics, Chinese Academy of Science, Beijing, 100049, China
4 Department of Material Physics and Chemistry, Beijing University of Science and Technology, Beijing 100083, China
5 Institute of Physics, Chinese Academy of Sciences, P.O.Box 603, Beijing 100080, China
6 Department of Mathematics, University of Texas-Pan American, Edinburg, TX 78541, USA
7 Department of Engineering Science and Materials, University of Puerto Rico at Mayaguez, PR 00681-9044, USA
The temperature-dependent structural changes were investigated by using the X-ray diffraction and the Extended X-ray absorption fine spectroscopy (EXAFS) for layered perovskite manganites La2-2xSr1+2xMn2O7 (x=0.33 and 0.4). The anomalous changes of Mn-O bond length and Jahn-Teller (J-T) distortion of MnO6 octahedron were observed, corresponding to ferromagnetic transition temperature (~ 120 K). Around the temperature of 2D short-range magnetic ordering (~ 235 K), there occurs an anomaly of the Jahn-Teller distortions of MnO6. These results indicate that magnetic properties of perovskite manganites La2-2xSr1+2xMn2O7 depend heavily on their microstructure change. The orbital state occupancy is involved in the observed Mn-O bond change.
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