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TT: Fachverband Tiefe Temperaturen

TT 10: Poster Session: Superconductivity

TT 10.9: Poster

Monday, March 14, 2011, 14:00–18:00, P4

Thermodynamic Investigations and Superconductivity in A(Fe_1−xCo_x)₂As₂ (A = Ba, Ca, K) Systems — •M. Abdel-Hafiez, L. Harnagea, S. Singh, S. Aswartham, C. Nacke, G. Friemel, M. Kumar, C. Hess, S. Wurmehl, R. Klingeler, A.U.B. Wolter, and B. Büchner — Leibniz Institut für Festkörper- und Werkstoffforschung IFW Dresden, 01069 Dresden, Germany

We report on thermodynamic properties of single crystals A(Fe_1−xCo_x)₂As₂ (A = Ba, Ca, K) combining magnetization, specific heat and resistivity investigations. In comparison to a similar phase diagram for Co-doped Ba122 and Ca122, which exhibits split quasicontinuous magnetic and structural transitions upon Co-doping, the parent compound KFe₂As₂ lacks such structural/magnetic transitions completely. Furthermore, its superconducting transition temperature has been determined to be around 3.8 K, while Ca122 and Ba122 systems only become superconducting upon doping. In addition to these doping-dependent studies, thorough investigations on the magnetic phase diagram have been performed on individual compounds of all three systems. The Werthamer-Helfand-Hohenberg model was used to determine the upper critical field for different directions H || c and H || (ab).