Fabrication and superconducting properties of nanostructured SFS contacts

Superconducting hybrid structures of submicrometer size utilizing high-melting transition metals such as Nb or Ta can be fabricated in ultra-high vacuum by means of a non-organic evaporation mask (Si3N4) of high thermal and mechanical stability. We report on the magnetic and superconducting properties of mesoscopic superconductor/ferromagnet/superconductor (SFS) junctions realized in a Nb/Cu/Co/Cu/Nb multilayer (ML). Below the superconducting transition temperature, the magnetic hysteresis loop shows a contribution from the strongly pinned magnetic flux of the superconducting Nb layers. Electrical transport measurements perpendicular to the layered structure clearly demonstrate a Josephson coupling between the Nb layers through the 5-nm thick ferromagnetic Co film.