Local structure of ReFeAsO (Re = La, Pr, Nd, Sm) oxypnictides studied by Fe K-edge EXAFSA. Iadecola1, S. Agrestini2, M. Filippi3, L. Simonelli4, M. Fratini1, B. Joseph1, D. Mahajan5, 6 and N. L. Saini1
1 Dipartimento di Fisica, Università di Roma “La Sapienza" - P. le Aldo Moro 2, 00185 Roma, Italy, EU
2 Laboratoire CRISMAT, CNRS UMR 6508, ENSICAEN - Boulevard du Marechal Juin, 14050 Caen, France, EU
3 Department of Physics and Astronomy, Vrije Universiteit - De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands, EU
4 European Synchrotron Radiation Facility - 6 Rue Jules Horowitz, BP 220, 38043 Grenoble Cedex 9, France, EU
5 Department of Materials Science and Engineering, State University of New York at Stony Brook Stony Brook, NY 11794, USA
6 Brookhaven National Laboratory - Upton, NY 11973, USA
received 22 June 2009; accepted in final form 9 July 2009; published July 2009
published online 5 August 2009
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.
61.05.cj - X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.
74.62.Bf - Effects of material synthesis, crystal structure, and chemical composition.
74.81.-g - Inhomogeneous superconductors and superconducting systems.
© EPLA 2009