Upper critical field anisotropy in Nb-Ti tapes

Nb47Ti tapes were prepared with various degrees of rolling and round-wire drawing after the final heat treatment. Rolling aligned the precipitates and produced 2D behavior in several tapes, as indicated by the development of anisotropy of the upper critical field H_c2. The anisotropy was observed prior to the onset of strong proximity coupling, as indicated by the change of the critical temperature T_c. These different dependencies resulted in one tape having a 9.5 K T_c and a 12.3 T H_c2 at 4.2 K in parallel field. Since the 2D behavior occurred prior to the optimization of flux pinning with increasing strain, the implications of 2D properties on the pinning force are discussed