Transport in superconductor/ferromagnet/superconductor junctions dominated by interface resistance

We report on high-sensitivity measurements performed on weakly resistive Nb/Al/Gd/Al/Nb ferromagnetic rare-earth-based junctions. High interface barriers in such junctions can strongly modify interplay between ferromagnetism and superconductivity. We show in the present paper that fur such ferromagnetic/superconductor junctions that the main contribution to the resistance comes from interface scattering. On the other hand, measurements on identical nonmagnetic rare-earth-based junctions such as Nb/Al/H/Al/Nb exhibit opposite behavior; hence most resistance comes from the bulk. A theoretical description of the temperature dependence of the superconductor/ferromagnet/superconductor (S/F/S) junction resistance is given through a temperature dependent Blonder-Tinkham-Klapwick theory for an energy range well below the superconducting gap scale of the Al/Nb bilayer. Such a theoretical description proves that interfacial scattering is of crucial importance when experimenting in S/F systems using gadolinium.