Evaluation of the specific boundary resistance of superconducting/weakly ferromagnetic hybrids by critical temperature measurements

Abstract

The specific boundary resistance, RB, of superconducting (S)/ferromagnetic (F) hybrids is obtained by measuring the dependence of the superconducting critical temperature, Tc, as a function of the thickness of the ferromagnetic layers, dF, and of the thickness of the superconducting layers, dS, in S/F bilayers and of the number of S/F bilayers, Nbil, for large values of Nbil, in F/[S/F]Nbil multilayers. We choose Nb for the superconducting material and two weakly ferromagnetic alloys, Cu0.38Ni0.62 and Pd0.81Ni0.19, for F. Analyzing the experimental results by using a matrix formulation of a theoretical model based on the Usadel equations, we are able to determine the value of RB which for both the S/F hybrids is of the order of 1 fΩm2.