Regensburg 2010 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 9: SC: Poster Session

TT 9.26: Poster

Montag, 22. März 2010, 14:00–18:00, Poster A

Phase diagram of Ca(Fe_1−xCo_x)₂As₂ single crystals — •Mahmoud Abdel-Hafez, Luminita Harnagea, Surjeet Singh, Norman Leps, Liran Wang, Gerd Friemel, Ulrike Stockert, Sabine Wurmehl, Günter Behr, Christian Hess, Rüdiger Klingeler, and Bernd Büchner — Leibniz Institute for Solid State and Materials Research IFW Dresden, D-01171 Dresden, Germany

We present specific heat, thermal expansion and magnetization data on Ca(Fe_1−xCo_x)₂As₂ single crystals grown from Sn-flux with 0≤ x ≤0.2. From our measurements we determine the phase diagram depicting the doping dependence of the structural/magnetic and superconducting transition temperatures. With increasing Co doping, the simultaneous first-order structural/magnetic transition at T₀=170 K of pristine CaFe₂As₂ is suppressed and superconductivity for x≥ 0.045 emerges. The optimal doping level was found to be x₀ ∼ 0.065. Below and above this value, the superconducting volume fraction diminishes rapidly. In contrast, the onset T_c remains rather unchanged for x < x₀ but decreases slowly to 10 K in the overdoped region of the phase diagram. These observations are discussed in the light of recent studies which show extreme pressure sensitivity of CaFe₂As₂ with a pressure induced T_c of 10 K.