Upper critical fields in superconductor-normal metal type superlattices in the Ginzburg-Landau approximation

The application of the Ginzburg-Landau theory to the superconductor-normal metal-superconductor (SNS) superlattices is considered in the case when normal and superconducting layers have the same thickness. The temperature dependences of the transverse and longitudinal upper critical fields are considered. The theoretical curves are compared with the available experimental results on SNS superlattices [C. Coccorese , Phys. Rev. B57, 7922 (1998)]. It is shown that the theoretical model can provide a correct interpretation of the experimental results with the minimum number of fitting parameters. The peculiarities of the order parameter behavior at the dimensional crossover in a parallel magnetic field as a function of the sample symmetry axis are discussed, and practical recommendations are given for an experimental verification of the role of symmetry of SNS-type structures. (C) 1999 American Institute of Physics. [S1063-777X(99)00412-0].