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

摘要

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 magneto resistance measurements in external magnetic field ranging from 0 to 16 T, at field orientations of 0 degrees, 25 degrees, 45 degrees, 60 degrees, and 90 degrees with respect to the broad face of the tape. It is shown that the H-irr and H-TAFF phase boundaries tend to shift to lower temperature region with increasing field angle. On the other hand, the H-FF curves remain roughly unaffected, leading to broadening of the unpinned liquid phase region between the H-TAFF and H-FF curves. Further analysis of the H-irr(T) data for theta = 90 degrees on the basis of Kim's model of pancake depinning has yielded a whole set of vortex parameters and H-c2 (theta). (c) 2005 Elsevier B.V. All rights reserved.