PREFERENTIAL POSITION FOR NUCLEATION OF ORDER-PARAMETER AND ANGULAR-DEPENDENCE OF UPPER CRITICAL FIELDS IN NB NBZR MULTILAYERS/

The Nb/NbZr multilayer is a typical one composed of two materials with the same bulk transition temperature and different electron diffusion constants and exhibits an anomalous upturn at T+ in the temperature d ependence of parallel upper critical field H-c2 parallel to(T) For all samples which show the upturn behavior in H-c2 parallel to(T), we hav e found the anomalous minimum and maximum at a tilt of angle theta = t heta and a perpendicular direction theta = 0, respectively. Of partic ular interest is the existence of a different tendency in the variatio n of theta and H-c2 perpendicular to-peak as a function of T below an d above T+. From our experimental results, we suggest the dimensional crossover of the localization of Delta(r) for a tilt of angle. The ang ular dependence of H-c2(T) has been in a good agreement with the numer ical calculations.