Electrical Characteristics of Nb Based Superconductor-Ferromagnet-Insulator-Superconductor Josephson Junctions

We have studied electrical characteristics of the Nb based Josephson junctions with a ferromagnetic (F) barrier layer which would be useful as an element of superconducting integrated circuits. A PdNi alloy with a Ni ratio of 11 at% was used as an F layer. The junctions showed a small standard deviation between 0.6% and 1.7% for the critical current (I-c) spread in a series array of 100 junctions. External magnetic field dependence of Ic showed homogeneity of the junction barrier layers, and effects of the magnetization in an F layer. On the other hand, a change in the film thickness of an F layer caused a drastic change in the critical current density.