Dresden 2006 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 11: Superconductivity: Heterostructures, Andreev Scattering, Proximity Effect, Coexistence
TT 11.2: Vortrag
Dienstag, 28. März 2006, 09:45–10:00, HSZ 301
Multiple 0 - π - transitions of Josephson - junctions with Ni3Al as weak ferromagnetic interlayer — •Frank Born1, M. Siegel1, E. Hollmann2, H. Braak3, C.M. Schneider3, and M.Yu. Kupriyanov4 — 1Institut für Mikro- und Nanoelektronische Systeme, Universität Karlsruhe (TH) — 2ISG2, Forschungszentrum Jülich GmbH — 3IFF, Forschungszentrum Jülich GmbH — 4Institute of Nuclear Physics, Moscow State University
Andreev - reflection is the central mechanism for the superconducting proximity effect. In a NS bi-layer the correlation of electron-like and hole-like quasi-particles decays exponentially with distance from the interface due to the de-phasing of its wave functions. In the case of a ferromagnetic material the Andreev - reflection picture is strongly modified: the spins of electron-like and hole-like quasi-particles are opposite orientated. This results under the influence of the exchange field in an energy shift and the creation of a nonzero momentum, leading to an additional spatially oscillation of the superconducting correlation amplitude. We report on experimental studies about superconducting coupling through a thin Ni3Al film. Depending on the deposition process the alloy is either only paramagnetic or it is magnetically ordered. In the paramagnetic regime the critical supercurrent, IC, decays exponentially over several nm, thus showing the pure proximity effect. In the ferromagnetic regime up to six damped oscillations of critical current on F-layer thickness was observed, revealing 0 - π - shifts in the ground state of Josephson junctions.