Decoupling of superconducting V by ultrathin Fe layers in V/Fe multilayers

We report on a detailed study of superconducting critical temperatures Tc and critical fields Hc2 of V/Fe multilayers. The thickness of the V layers (dV) and Fe layers (dFe) as well as the total number of layers in the multilayer (N) were varied systematically. For dFe0.6 nm, at constant dV, Tc and the critical fields for parallel (Hc2) and perpendicular (Hc2) orientation do not depend on either dFe or N, and a two-dimensional (2D) temperature dependence for Hc2 without 3D-2D crossover is observed for small values of dV. The predicted oscillatory behavior of Tc as a function of dFe is not found. We conclude that the superconducting V layers are completely decoupled by only 0.6 nm Fe, in conflict with previous reports. Upon decreasing dV at constant dFe, a strong decrease of Tc is found. This, together with the temperature dependence of Hc2 and Hc2 for all samples can be described by existing theory.