title: Local structural investigation of SmFeAsO₁₋xF(x) high temperature superconductors.
abstract: A strong revitalization of the field of high temperature superconductivity (HTSC) has been induced recently by the discovery of T(C) around 26 K in F-doped LaFeAsO iron pnictides. Starting from this discovery, a huge amount of experimental data have been accumulated. This important corpus of results will allow the development of suitable theoretical models aimed at describing the basic electronic structure properties and nature of superconducting states in these fascinating new systems. A close correlation between structural features and physical properties of the normal and superconducting states has already been demonstrated in the current literature. Advanced theoretical models are also based on the close correlation with structural properties and in particular with the Fe-As tetrahedral array. As for other complex materials, a deeper understanding of their structure-properties correlation requires a full knowledge of the atomic arrangement within the structure. Here we report an investigation of the local structure in the SmFeAsO₁₋ xF(x) system carried out by means of x-ray total scattering measurements and pair distribution function analysis. The results presented indicate that the local structure of these HTSC significantly differs from the average structure determined by means of traditional diffraction techniques, in particular the distribution of Fe-As bond lengths. In addition, a model for describing the observed discrepancies is presented.
authors.affiliation: Dipartimento di Chimica-Sezione di Chimica Fisica, INSTM (UdR Pavia), Università di Pavia, Viale Taramelli 16, 27100 Pavia, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Malavasi
authors.forename: Gianluca A
authors.initials: GA
authors.lastname: Artioli
authors.forename: Hyunjeong
authors.initials: H
authors.lastname: Kim
authors.forename: Beatrice
authors.initials: B
authors.lastname: Maroni
authors.forename: Boby
authors.initials: B
authors.lastname: Joseph
authors.forename: Yang
authors.initials: Y
authors.lastname: Ren
authors.forename: Thomas
authors.initials: T
authors.lastname: Proffen
authors.forename: Simon J L
authors.initials: SJ
authors.lastname: Billinge