Dresden 2009 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 40: Superconductivity: Ferropnictides 1
TT 40.4: Talk
Thursday, March 26, 2009, 14:45–15:00, HSZ 03
Thermodynamic study of the Co-doped Ba-122 iron pnictide — •Frédéric Hardy1, Christoph Meingast1, Thomas Wolf1, Rolf Heid1, Peter Adelmann1, Peter Schweiss1, Doris Ernst1, and Hilbert v. Löhneysen1,2 — 1Forschungszentrum Karlsruhe, Institut für Festkörperphysik, 76021 Karlsruhe, Germany — 2Physikalisches Institut, Universität Karlsruhe, 76128 Karlsruhe, Germany
Since the discovery of the new high-Tc iron pnictides, many scenarios were put forward to describe the symmetry of the order parameter including d-wave and unconventional s-wave. Early heat capacity measurements suggested that the electron-doped 1111 compounds show a nodal gap, while K-hole-doped 122 materials are fully gapped. Here we present a critical analysis of our own specific-heat data on Co-doped 122 single crystals, in which we pay particular attention to the details of the phonon background subtraction as well as to the contribution of impurity phases. We also discuss an interesting field-dependence of the thermal expansivity below Tc(H).