Properties of superconductivity for decoupled ferromagnet/superconductor trilayers and multilayers in Fe/Nb system

Abstract

The transition temperature T(c) and upper critical field H(c2) of sputtered Fe/Nb trilayers and multilayers have been determined by measurement of electrical resistivity. For a fixed Fe layer thickness, T(c) decreases with decreasing Nb thickness up to a critical thickness d(Nb)(crit) approximate to 34 nm below which superconductivity vanishes. When the superconducting layers are thin (d(Nb) < 140 nm) and decoupled by pair breaking in the ferromagnetic layers, the parallel critical field exhibits nonlinear temperature dependence, revealing a change in the superconducting dimensionality. The strong decrease of T(c) with decreasing Nb thickness as well as the temperature dependence of H(c2) can be well described by theoretical model. (C) 2006 Elsevier B. V. All rights reserved.