IRREVERSIBILITY FIELD ANALYSIS FOR BI2SR2CA2CU3OX TAPES BY USING AXIAL PROBE

An axial probe for evaluation of J(c) = f(B, T, theta) was designed an d fabricated. The probe is capable of carrying currents over 250 A in a magnetic field up to 13 T. The critical current density of 61 filame nt Bi2223 tape was measured by this probe in a temperature range of fr om 10 to 100 K for two orientations of the magnetic field. Obtained re sults confirm high sensitivity of the superconductor to the field, esp ecially for B perpendicular to tape surface, Moreover, the J(c) = f(B) dependence reveals a logarithmic relationship and it is in good agree ment with the scaling law proposed by Kobayashi ei al. [S. Kobayashi, T. Kaneko, T. Kato, J. Fujikami, K. Sate, Physica C 258 (1996) 336]. D erived irreversible lines show temperature dependence as B-irr proport ional to [1 - T/T-c](n), with a distinct kink observed at higher tempe ratures. The transition from n = 1.65 to n = 3 is believed to represen t crossover from the weakly to the highly correlated regime of fluxoid s. (C) 1998 Elsevier Science B.V. All rights reserved.