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TT: Fachverband Tiefe Temperaturen

TT 45: Superconductivity: Ferropnictides 2

TT 45.8: Talk

Friday, March 27, 2009, 12:15–12:30, HSZ 03

Absorption spectroscopy of rare earth oxypnictides — •Friedrich Roth¹, Thomas Kroll¹, Andreas Koitzsch¹, Roberto Kraus¹, Günter Behr¹, Guoli Sun², Dunlu Sun², Chengtian Lin², Bernd Büchner¹, and Martin Knupfer¹ — ¹Institute for Solid State Research, IFW-Dresden, P.O. Box 270116, D-01171 Dresden, Germany — ²Max-Planck-Institute for Solid State Research, Heisenbergstraße 1, D-70569 Stuttgart, Germany

A large oxypnictides family LnFeAsO (Ln= La, Ce, Pr, Nd, Sm, Gd) has been found to be superconducting with a transition temperature up to 55K and high upper critical fields. The onset of the superconducting critical temperature T_c in these compounds increases with the reduction of the rare-earth ionic size, and the highest T_c obtained so far is 55K in doped SmFeAsO. In this contribution we present results of x-ray absorption (XAS) spectroscopy measurements on the soft X-ray regime for polycrystalline LaFeAsO, CeFeAsO, SmFeAsO and GdFeAsO at various temperature as well as for Ba_1−xK_xFe₂As₂ single crystals.