Upper critical field of Nb/Pd1-xFex/Nb triple layers

The parallel upper critical field Bc2∥(T) of Nb/Pd1-xFex/Nb triple layers exhibits with increasing interlayer thickness and/or increasing Fe concentration x a transition from two-dimensional (2D) behavior of the whole sandwich, where the Nb films are coupled across the ferromagnetic interlayer, to a 2D behavior of decoupled Nb films. The interlayer thickness dc, above which no transition is observed drops precipitously from ∼ 100 to 15 Å around x ≈ 0.1 and remains nearly constant up to x = 1. This change is most probably associated with a change of the interlayer from paramagnetic to ferromagnetic order with increasing x. © 2000 Elsevier Science B.V. All rights reserved.