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TT: Fachverband Tiefe Temperaturen

TT 5: Postersession Superconductivity: Materials - Fabrication and Properties

TT 5.31: Poster

Montag, 23. März 2009, 13:00–16:45, P1A

Superconductivity and magnetism in the oxypnictides: high field ESR and µSR studies of (La,Gd)FeAsO_1−xF_x compounds — •Ferenc Murányi^1,2, Alexey Alfonsov², Vladislav Kataev², Anke Köhler², Jochen Werner², Günter Behr², Norman Leps², Rüdiger Klingeler², Agnieszka Kondrat², Christian Hess², Bernd Büchner², Rustem Khasanov³, Hubertus Luetkens³, and Hans-Henning Klaus⁴ — ¹Physics Institute, University of Zürich, Winterthurerstr. 190, 8057 Zürich, Switzerland — ²IFW Dresden, Helmholtzstraße 20, 01069 Dresden, Germany — ³Paul Scherrer Institut, 5232 Villigen PSI, Switzerland — ⁴IFP, TU Dresden, D-01069 Dresden, Germany

The discovery of a new class of superconducting materials, ReFeAsO_1−xF_x, stirred up the scientific community. Here we report the Gd³⁺ high field ESR study of differently doped (La,Gd)FeAsO_1−xF_x compounds. In lightly Gd-doped LaFeAsO samples the SDW transition yields line-broadening at the transition temperature, the SDW transition is then suppressed upon F-doping. In the dense compound, GdFeAsO, with SDW transition around 140 K, the Gd-ESR was also studied. With 15% F-doping superconductivity appears at ∼ 21 K. The SDW and SC transitions are clearly seen in ESR and in µ SR as well. Surprisingly the reminiscence of the SDW transition of the undoped material (GdFeAsO) was identified in the doped (15% F) compound at lower temperature (∼ 80 K). This indicates the importance of the the interplay between superconductivity and magnetism in oxypnictides.