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

The specific boundary resistance, R B, of superconducting (S)/ferromagnetic (F) hybrids is obtained by measuring the dependence of the superconducting critical temperature, T c, as a function of the thickness of the ferromagnetic layers, d F, and of the thickness of the superconducting layers, d S, in S/F bilayers and of the number of S/F bilayers, N bil, for large values of N bil, in F/ [S/F] N bil multilayers. We choose Nb for the superconducting material and two weakly ferromagnetic alloys, Cu 0. 38 Ni 0. 62 and Pd 0. 81 Ni 0. 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 R B which for both the S/F hybrids is of the order of 1 f m 2. © 2011 American Institute of Physics.