The temperature dependence of the perpendicular upper critical field B-c2perpendicular to of a single superconducting Nb film (S) sandwiched between insulating (I) and/or normal-metal layers (N = Cu) is investigated. For the ISI configuration, B-c2perpendicular to exhibits the usual linear T-dependence near the transition temperature T, in contrast to the NSI and NSN configurations There a positive curvature of B-c2perpendicular to(T) is observed near T-c. This demonstrates the influence of the different boundary conditions on the B-c2perpendicular to(7) behavior of a single S film in contact with N or L Deviations from the linear T-dependence are thus attributed to the proximity effect due to the presence of an N-S boundary. (C) 2001 Elsevier Science B.V. All rights reserved. [References: 27]
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