Variation of vortex structure characteristics of Bi-2223/Ag superconducting tapes with respect to applied magnetic field direction

A study of the effects of external magnetic field orientation on the vortex characteristics was performed on a Bi-2223/Ag superconducting tape prepared by powder in tube method incorporating two-axial rolling and eccentric rolling processes. The data used for the analysis were obtained by magnetoresistance measurements in external magnetic field ranging from 0 to 16 T, at field orientations of 0°, 25°, 45°, 60°, and 90° with respect to the broad face of the tape. It is shown that the Hirr and HTAFF phase boundaries tend to shift to lower temperature region with increasing field angle. On the other hand, the HFF curves remain roughly unaffected, leading to broadening of the unpinned liquid phase region between the HTAFF and HFF curves. Further analysis of the Hirr(T) data for θ = 90° on the basis of Kim's model of pancake depinning has yielded a whole set of vortex parameters and Hc2 (θ).