TEMPERATURE-DEPENDENCE OF THE CRITICAL-CURRENT DETERMINED FROM MAGNETIC-RELAXATION IN HGBA2CA2CU3O8+DELTA

Based on the U(j) relation of the collective pinning theory, U(j) = [U -c/mu][(j(c)/j)(mu) - 1], we introduce a direct method to derive the t emperature dependence of the characteristic exponent mu, the collectiv e pinning energy U-c and the critical current density j(c) from magnet ic relaxation measurement. By utilizing a linear relation between 1/R = 1//partial derivative ln j/partial derivative ln t/ and ln t at a fi xed temperature, mu and U-c are easily obtained. Inserting these param eters into U(j) we can extract j(c). So mu(T), U-c(T) and j(c)(T) are able to be derived from relaxation measurements at different temperatu res. This method was applied to a HgBa2Ca2Cu3O8+delta superconductor. The results were discussed within the collective pinning and creep the ory. (C) 1998 Elsevier Science B.V.