Regensburg 2007 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 8: Superconductivity - Poster Session

TT 8.32: Poster

Montag, 26. März 2007, 14:00–17:45, Poster A

Investigation of dynamic effects in 0, π and 0-π SIFS Josephson junctions — •Judith Pfeiffer¹, Edward Goldobin¹, Martin Weides², Matthias Kemmler¹, Andreas Dewes¹, Dieter Koelle¹, and Reinhold Kleiner¹ — ¹Universität Tübingen, Experimentalphysik II, Auf der Morgenstelle 14, D-72076 Tübingen, Germany — ²Forschungszentrum Jülich GmbH, Institut für Festkörperforschung, 52425 Jülich

We present experimental and numerical studies of high quality underdamped SIFS Josephson junctions (JJ) fabricated as Nb/Al₂O₃/Cu₄₀Ni₆₀/Nb heterostructures. Varying the thickness of the ferromagnetic barrier we can create 0, π and 0-π junctions. From measurements of the current voltage characteristic (IVC) and critical current I_c vs. magnetic field H we find record values for the critical current density j_c in the π-state. The I_c(H) data for the 0-π JJ show a clear minimum at H=0. Dynamical phenomena such as Fiske steps and zero field steps are visible on the IVCs. In the case of the 0-π junction we are able to detect a half-integer zero field step due to the dynamics of a semifluxon. The dissipation in all these JJs is not linear, but the linear part decreases exponentially with a decreasing temperature in the range between 4.2 and 2.1 K.