Upper critical magnetic fi eld of KxFe2-ySe2 and Eu0.5K0.5Fe2As2 single crystals

V.A. Gasparov (1) , Alain Audouard (2) , Loïc Drigo (2) , A.I. Rodigin (3) , C.T. Lin (4) , W.P. Liu (4) , M. Zhang (5) , A. F. Wang (6) , X.H. Chen (6) , H.S. Jeevan (7) , J. Maiwald (7) , P. Gegenwart (7)

1 ISSP - Osipyan Institute of Solid State Physics
2 LNCMI-T - Laboratoire national des champs magnétiques intenses - Toulouse
3 MSU - Lomonosov Moscow State University
4 Max Planck Institute for Solid State Research
5 ISCR - Institut des Sciences Chimiques de Rennes
6 USTC - University of Science and Technology of China [Hefei]
7 Georg-August-University = Georg-August-Universität Göttingen

The H-T phase diagrams of single crystalline electron-doped K0.83Fe1.83Se2 (KFS1), K0.8Fe2Se2(KFS2) and hole-doped Eu0.5K0.5Fe2As2 (EKFA) have been deduced from tunnel diode oscilla-tor-based contactless measurements in pulsed magnetic fields up to 57 T for the inter-plane (H//c) and in-plane (H//ab) directions. The temperature dependence of the upper critical mag-netic field Hc2(T) relevant to EFKA is accounted for by the Pauli model including an anisotropic Pauli paramagnetic contribution (BHp=114 T for H//ab and 86 T for H//c). This is also the case of KFS1 and KFS2 for H//ab whereas a significant upward curvature, accounted for by a two-gap model, is observed for H//c. Despite the presence of antiferromagnetic lattice order within the superconducting state of the studied compounds, no influence of magnetic ordering on the temperature dependence of Hc2(T) is observed.

Domaines: Supraconductivité [cond-mat.supr-con]

V.A. Gasparov, Alain Audouard, Loïc Drigo, A.I. Rodigin, C.T. Lin, et al.. Upper critical magnetic fi eld of KxFe2-ySe2 and Eu0.5K0.5Fe2As2 single crystals. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2013, 87, pp.094508. ⟨10.1103/PhysRevB.87.094508⟩. ⟨hal-00825700⟩