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

We report on a detailed study of superconducting critical temperatures T, and critical fields H, 2 of V/Fe multilayers. The thickness of the V layers (dv) and Fe layers (dF, ) as well as the total number of layers in the multilayer (N) were varied systematically. For dF, «0.6 nm, at constant dv, T, and the critical fields for parallel (H, 2~~) and perpendicular (H,») orientation do not depend on either dF, or N, and a two-dimensional (2D) temperature dependence for H, 2I~ without 3D-2D crossover is observed for small values of dv. The predicted oscillatory behavior of T, as a function of dF, is not found. %"e conclude that the superconducting V layers are completely decoupled by only 0.6 nm Fe, in con6ict with previous reports. Upon decreasing dv at constant dF„a strong decrease of T, is found. This, together with the temperature dependence of H, &~~ and H, » for all samples can be described by existing theory.