QUASI-PERIODIC SUPERCONDUCTING V ZR MULTILAYERS - CRITICAL MAGNETIC-FIELDS AND CROSSOVER/

Critical magnetic fields parallel and perpendicular to the planes of q uasiperiodic superconducting Fibonacci multilayers (ML) consisting of vanadium and zirconium are measured. The temperature dependence of the parallel critical field H-c parallel to displays two crossovers. The H-c parallel to(T) dependence is of square-root type in the vicinity o f the transition temperature T-c and linear at low temperatures. Betwe en these temperature intervals, the dependence follows a power law: H( c parallel to)similar to(1-T/T-c)(alpha), alpha = 0,78+/-0,02. The com plex nature of this dependence can be explained in the framework of th e Ginzburg-Landau theory for a quasiperiodic ML, as well as by the sca ling theory for fractal multilayers which takes into account the diffe rent structure length scales in the case of ML with a complex sequence of layers. (C) 1998 American Institute of Physics. [S1063-777X(98)004 08-3].