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• 作者：Sami H. Mahmood ; Jumana Dawood ; Abdel-Fatah Lehlooh ; Abdelwaheb Cheikhrouhou and Abdallah Ammar
• 关键词：M枚ssbauer spectroscopy ; Manganites ; Polarons ; Charge order ; Jahn– ; Teller distortion ; Delocalization
• 刊名：Hyperfine Interactions
• 出版时间：February, 2010
• 出版年：2010
• 期刊代码：18_03043843
• 类别：cp
• 卷：196
• 期：1-3
• 页码：385-394
• 数据来源：sp

摘要

In this work we report the results of X-ray diffraction and M枚ssbauer spectroscopy for the systems Pr<sub>0.5sub>Sr<sub>0.5sub>Mn<sub>1 − x sub>Fe<sub> x sub>O<sub>3sub> (with x = 0.05, 0.10, 0.15, 0.20, 0.25, 0.30). XRD patterns indicated that all samples were single phase with slightly distorted orthorhombic symmetry. Room temperature M枚ssbauer spectra are all quadrupole split, indicating paramagnetic relaxation of the Fe moment for all values of Fe concentrations. The spectra are fitted with two doublet components associated with Fe3 +  ions in octahedral sites with different distortions. M枚ssbauer spectra recorded at liquid nitrogen temperature for this system also indicate paramagnetic relaxation of the Fe moments down to liquid nitrogen temperature (LNT). In these spectra a third quadrupole component with quadrupole splitting close to zero develops. This component is associated with the delocalization of the charge carriers and the consequent disappearance of lattice distortions produced by the polaronic effect at room temperature. The component with the high quadrupole splitting (0.81 to 1.07 mm/s) results from Jahn–Teller distortion as a consequence of charge ordering transition at low temperature.