ANISOTROPY OF THE LOWER CRITICAL-FIELD IN NB CU MULTILAYER/

Lower critical fields parallel and perpendicular to the layers of the superconducting Nb(200 angstrom)/Cu(150 angstrom) multilayer were meas ured in the temperature range from T(c) = 7.2K down to 2K. The anisotr opy of the lower critical field for the S/N multilayer was obtained fo r the first time. The anisotropy exhibited a sharp upturn at T approxi mately 5.5K. This temperature was found to coincide with the temperatu re of 3D-2D crossover obtained from the measurements of the upper crit ical field.