Resistivities and mean-free paths in individual layers of a metallic multilayered structure.

There exists in the literature a number of transport measurements performed on metallic superlattices. In this paper a method is proposed which, given such measurements performed at two different temperatures, allows determination of resistivities and mean-free paths (m.f.p.) of carriers in individual layers comprising a superlattice. The method is illustrated for Nb/ Al (author's data) Cu (data of 1. Schuler and co-workers). The behavior of m.f.p. in individual layers as a function of layer thickness turns out to be both unexpected and instructive. In particular, we find that in all cases except for Cu in Nb/Cu, the m.f.p. is significantly (factor of 2-3) smaller than the layer thickness. Previously, for the lack of such information, it was uniformly assumed that the m.f.p. is limited by the layer thickness, L ~ d. Knowledge of the m.f.p. is important for interpretation of various experiments on metallic superlattices, in particular for better understanding of superconducting proximity systems and tunneling measurements.