The local structure of the Ca_0.9Pr_0.1Fe₂As₂ superconductor as a function of temperature

We have studied the local structure of Ca_0.9Pr_0.1Fe₂As₂, showing filamentary superconductivity above 40 K, by a combined analysis of Fe K-edge and As K-edge extended X-ray absorption fine structure measurements. The experiments are performed as a function of temperature exploiting a single crystal sample and in-plane polarization of the X-ray beam to extract information on the directional displacements. The local structure of the FeAs layer is found to be consistent with a regular FeAs₄ tetrahedron containing negligible local disorder. Unlike other superconducting systems, we do not find any change in the atomic displacements across the superconducting transition temperature. The results are compatible with electron doping induced intrinsic superconductivity of optimized FeAs₄ local structure containing negligible disorder.