Volume 87, Number 2, July 2009
Article Number 26005
Number of page(s) 5
Section Condensed Matter: Structural, Mechanical and Thermal Properties
Published online 05 August 2009
EPL, 87 (2009) 26005
DOI: 10.1209/0295-5075/87/26005

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

A. 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