Proximity Effect in NiCu-Based Josephson Tunnel Junctions

We present experimental results concerning both the fabrication and the characterization of superconducting tunnel junctions based on Nb/NiCu superconductor/ferromagnet (S/F) bilayers. Josephson junctions have been characterized down to T=1.4 K in terms of current-voltage I-V characteristics, Josephson critical current vs magnetic field, role of external magnetic field. Proximity parameters of the bilayer, such as the coherence length and the exchange field energy of the F metal, have been estimated by means of a numerical deconvolution of the I-V data the electronic density of states on both sides of the S/F bilayer. Results have been compared with theoretical predictions from a proximity model for S/F bilayers in the dirty limit in the framework of Usadel equations for the S and F layer, respectively.