Regensburg 2004 – scientific programme

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TT: Tiefe Temperaturen

TT 19: Supraleitung: Heterostrukturen, Andreev-Streuung, Proximity-Effekt, Koexistenz

TT 19.2: Talk

Wednesday, March 10, 2004, 17:15–17:30, H20

Ferromagnetic/Superconducting Bilayer Structure: A Model For Spin Diffusion Length Estimation — •Soltan Soltan, Joachim Albrecht, and Hanss-U. Habermeier — Max Planck Institut für Festkörperforschung, Heisenbergstr.1, D 70569 Stuttgart, Germany

Epitaxial bilayer structures of La_2/3Ca_1/3MnO₃ (LCMO) and YBa₂Cu₃O_7−δ (YBCO) are grown on single crystalline SrTiO₃ substrates by pulsed laser deposition. The microstructure is analyzed by XRD and exhibits c-axis oriented growth. The properties of these samples are investigated by current transport and magnetization measurements. We find that the transition temperature of the superconductor strongly depends on the thickness of the YBCO film which can be explained by the tunnelling of spin polarized quasiparticles from the magnetic film into the superconductor. A theoretical model has been developed that fits the experimental data quite well and allows us to determine the spin diffusion length to be in the order of 10 nm. Furthermore we observe a shift of the Kosterlitz-Thouless transition temperature close to T_c in case of the injection of an additional transport into the bilayers.