Berlin 2008 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 11: Superconductivity: Tunneling, Josephson Junctions, SQUIDs
TT 11.4: Talk
Monday, February 25, 2008, 16:15–16:30, H 3010
Self resonances in Josephson π-junctions — •Georg Wild, Achim Marx, and Rudolf Gross — Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
Due to their potential application as π-phase shift elements Josephson junctions with ferromagnetic interlayer have attracted much interest. We have developed a self-aligned multilayer process for the fabrication of superconductor/insulator/ferromagnetic metal/superconductor (SIFS) Josephson junctions (S=Nb, I=Al2O3, F=NiPd). Our junctions show RCSJ-like current-voltage characteristics (IVCs) and a Fraunhofer diffraction pattern for the magnetic field dependence of the critical current Ic. The dependence of the Ic Rn-product on the ferromagnet thickness shows a clear crossover between the zero- and the π-state. The π-coupled multilayers show critical current densities of about 50 A/cm2 and Ic Rn-products of about 20 µV at T=1.5 K.
The IVCs of these junctions show both Fiske resonances and zero field steps. The height of the Fiske steps can be fitted by Kulik’s theory. Fitting the measured height of the Fiske steps of different order we derived quality factors varying between 20 and 40.
This work was supported by the DFG via SFB 631 and the Excellence Initiative via NIM.