(d-wave) and Pb (s-wave) superconductors. The first unambiguous proof of a Josephson junction with a ferromagnetic barrier was given only a decade later. That work used a weak ferromagnet consisting of a copper-nickel alloy (CuxNi1−x, with x around 0.5) and optimized it so that the Curie temperature was close to the superconducting transition temperature of the superconducting niobium leads. See also Josephson effect φ Josephson junction Semifluxon Fractional vortices Brian D. Josephson References Superconductivity Josephson effect