Fabrication and Characterization of Short Josephson Junctions with Stepped Ferromagnetic Barrier

Uthayasankaran Peralagu and Martin Weides

Institute for Solid State Research, Research Centre Juelich, 52425Juelich, Germany
e-mail: m.weides@fz-juelich.de; 0307850P@student.gla.ac.uk

Abstract—We present novel low-T_c superconductor-insulator-ferromagnet-superconductor (SIFS) Josephson junctions with planar and stepped ferromagnetic interlayer. We optimized the fabrication process to set a step in the ferromagnetic layer thickness. Depending on the thickness of the ferromagnetic layer the ground state of the SIFS junction has a phase drop of either 0 or π. So-called 0–π Josephson junctions, in which 0 and π ground states compete with each other, were obtained. These stepped junctions may have a double degenerate ground state, corresponding to a vortex of supercurrent circulating clock- or counterclockwise and creating a magnetic flux which carries a fraction of the magnetic flux quantum Φ₀. Here, we limit the presentation to static properties of short junctions.

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Manuscript received January 3, 2008; accepted January 17, 2008.  Reference No. ST27; Category 4.