Effect of geometrical symmetry on the angular dependence of the critical magnetic field in superconductor/normal metal multilayers

摘要

The angular dependence of the upper critical field, Hc , for Nb/Pd multilayers with different geometricaludsymmetries i.e., with an even or an odd number of bilayers, Nbil and thickness of Nb and Pd layers of theudorder of superconducting coherence length were investigated the angle is here defined from the planeudparallel to the sample surface . The presence of an angular dimensional crossover at some temperature dependentudangle * T was established. At angles * T the multilayers are in two-dimensional mode while atud * T they are in a three-dimensional one. In addition, the sample with odd Nbil has a larger value ofud * T with respect to the sample with even Nbil. The experimental results have been qualitatively explained inudthe framework of the Ginzburg-Landau theory. It was shown that the main features of the Hc dependencesudin samples with even and odd Nbil values are related to the different localizations of the superconducting orderudparameter.