ANGULAR-DEPENDENCE OF THE UPPER CRITICAL-FIELD IN NB CUMN MULTILAYERS/

We present data related to the temperature (T) and angular (theta) dep endencies of the upper critical field (H-c2) Of Nb(Superconductor)-CuM n(spin glass) multilayers as a function of CuMn layer thickness and Mn concentration. We observe two-dimensional (2D) behavior for large CuM n thickness. As the CuMn layer thickness is decreased, the H-c2(T) cur ves correspond to three-dimensional (3D) behavior, while the H-c2(thet a) dependencies measured in the range [-1.5 degrees, + 1.5 degrees] an more sensitive to the dimensionality of the system. In particular, th e experimental data reveal a 3D --> 2D crossover at very low angle whe n the Mn percentage is increased at fixed CuMn thickness. This behavio r can be related to vortex dimensionality change in anisotropic superc onductors.