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TT: Fachverband Tiefe Temperaturen

TT 34: Superconductivity - Vortex Dynamics, Vortex Phases, Pinning

TT 34.10: Vortrag

Freitag, 30. März 2007, 12:45–13:00, H19

Critical currents in high-temperature superconductor/ferromagnet heterostructures — •Märit Djupmyr¹, Soltan Soltan^2,3, Hanns-Ulrich Habermeier², and Joachim Albrecht¹ — ¹Max-Planck-Institut für Metallforschung, Heisenbergstr. 3, D-70569 Stuttgart — ²Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart — ³Physics Department, Faculty of Science, Helwan University, 11795 Cairo, Egypt

The critical current in bilayer structures consisting of high-temperature superconducting YBa₂Cu₃O_7−δ(YBCO) and ferromagnetic La_2/3Ca_1/3MnO₃ thin films, is substantially influenced by the presence of the ferromagnetic layer at low temperatures. Using quantitative magneto-optics a detailed analysis of the temperature dependence of the critical currents is done in the range T=10-90 K, giving information about the mechanisms of flux line pinning. For YBCO thin films, different current limiting mechanisms have been found depending on temperature and microstructure. For temperatures above T=40 K thermal depinning of flux lines is most important for the YBCO thin films as for the bilayers. Below T=40 K, the granularity of the film plays an important role for the current transport in the YBCO thin film and the ferromagnetic layer strongly affects the critical current in the bilayer.