Berlin 2012 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 17: Superconductivity: Fe-based Superconductors - 122 Part 2 & Theory

TT 17.2: Talk

Tuesday, March 27, 2012, 09:45–10:00, H 2053

Electronic phase diagram of Co-doped BaFe₂As₂ films prepared by PLD — •Fritz Kurth, Kazumasa Iida, Jens Hänisch, Steffen Oswald, Konstantin Nenkov, Jochen Werner, Ludwig Schultz, Bernhard Holzapfel, and Silvia Haindl — IFW Dresden, Helmholtzstrasse. 20, 01069 Dresden; Germany

Ba(Fe_1−xCo_x)₂As₂ thin films with different Co-concentrations, x, were prepared on Fe-buffered MgO(100) substrates using pulsed laser deposition under ultra high vacuum conditions. All films were grown epitaxially with high phase purity as confirmed by X-ray diffraction. The c-axis lattice parameter was observed to decrease with increasing x, as observed as well in bulk material. The superconducting transition temperature, T_c, shows the typical dome shaped dependence on x where the maximum T_c of over 26 K is found at a doping level of x = 0.044, which is different from the results observed on single crystals and bulk pellets. This difference might be due to a change in the Co or As stoichiometry in the films compared to the nominal target compositions. A detailed chemical analysis by Auger electron spectroscopy reveals Co diffusion into the Fe buffer. At high deposition temperatures a large gradient of the Co-content is observed from 18,2 % to 8,7 %. Finally, transport properties of the doping series will be presented in this talk. This work was supported by DFG under Project no. HA5934/3-1.