Local structure of ReFeAsO (Re=La, Pr, Nd, Sm) oxypnictides studied by Fe K-edge EXAFS

• Published in: Europhysics letters Vol. 87; no. 2; pp. 26005 - p1-5
• Main Authors: Iadecola, A, Agrestini, S, Filippi, M, Simonelli, L, Fratini, M, Joseph, B, Mahajan, D, Saini, N. L
• Format: Journal Article
• Language: English
• Published: United States IOP Publishing 01.07.2009; EDP Sciences
• Subjects: 61.05.cj; 74.62.Bf; 74.81.-g; ABSORPTION; BOND LENGTHS; ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; FINE STRUCTURE; FLUORESCENCE; MAGNETISM; SUPERCONDUCTIVITY
• ISSN: 0295-5075; 1286-4854
• DOI: 10.1209/0295-5075/87/26005

Local structure of ReOFeAs (Re = La, Pr, Nd, Sm) system has been studied as a function of chemical pressure varied due to different rare-earth size. Fe K-edge extended X-ray absorption fine structure (EXAFS) measurements in the fluorescence mode has permitted to compare systematically the inter-atomic distances and their mean square relative displacements (MSRD). We find that the Fe-As bond length and the corresponding MSRD hardly show any change, suggesting the strongly covalent nature of this bond, while the Fe-Fe and Fe-Re bond lengths decrease with decreasing rare-earth size. The results provide important information on the atomic correlations that could have direct implication on the superconductivity and magnetism of ReOFeAs system, with the chemical pressure being a key ingredient.