Temperature-dependent local structure of LaFeAsO1−xFx: Probing the atomic correlations

T. A. Tyson, T. Wu, J. C. Woicik, B. Ravel, A. Ignatov, C. L. Zhang, Z. Qin, T. Zhou, S.-W. Cheong
2010 Journal of Applied Physics  
The local structure of the parent and doped LaFeAsO 1−x F x ͑pnictide͒ compounds were studied by x-ray absorption spectroscopy and density functional methods. In the doped system, the Fe-As and Fe-Fe correlations are both well modeled by an Einstein model. For the Fe-As bonds, the Einstein temperatures are identical for the doped ͑11%͒ and undoped samples but the doped sample is found to have a lower level of static disorder. Doping is found to increases the effective Einstein temperature of
more » ... Fe atomic correlation. The results suggest that the onset of superconductivity in the F doped system may be related to enhanced magnetic interactions. Density functional calculations of the total charge density reveal strong bonding between neighboring As ions but metal-like behavior in the Fe layers. It is also seen directly that the replacement of oxygen by fluorine modifies the electron charge density mainly on the Fe sites.
doi:10.1063/1.3525999 fatcat:fnwkpge5wbea7httjfxrhi742y