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TT: Fachverband Tiefe Temperaturen

TT 8: Superconductivity - Poster Session

TT 8.4: Poster

Monday, March 26, 2007, 14:00–17:45, Poster A

High-Resolution Specific-Heat data of YBa₂Cu₃O_x up to 400 K — •Christoph Meingast¹, Akira Inaba², Thomas Wolf¹, Volker Pankoke¹, Rolf Heid¹, and Klaus-Peter Bohnen¹ — ¹Forschungszentrum Karlsruhe, Institut für Festkörperphysik, D-76021 Karlsruhe, Germany — ²Research Center for Molecular Thermodynamics, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan

Very accurate (0.1 percent) adiabatic specific heat measurements up to 400 K have been made on YBa₂Cu₃O_x samples with oxygen contents x = 6.7, 6.9 and 7.0. The oxygen deficient samples clearly show an anomaly due to the oxygen ordering above room temperature. In order to analyze this oxygen-ordering contribution, as well as the electronic contribution, in detail, the phonon contribution, obtained by first-principles electronic structure calculations, was subtracted from the data. This subtraction works quite well, which demonstrates the quality of both the measured and calculated heat capacities.