Temperature, current and field dependencies of activation energy in Tl2Ba2CaCu2O8 superconducting thin film

The dynamic magnetic hysteresis loops m(T, B-a, (B) over dot(a)) of an epitaxial Tl2Ba2CaCu2O8 superconducting thin film are measured at various field sweep rates (B) over dot(a) and at temperatures ranging from (1/2)T-c to (4/5)T-c. The magnetization current densities J(m)(T, B-a, (B) over dot(a)) are obtained using the Bean model approximation. Followed by the determination of the maximum creep velocity for fluxons or flux bundles, the optimum temperature, current and field dependent functions of the effective activation energy, g(T), F(J(m)) and B-a(gamma) are uniquely determined for a range of temperatures and applied fields. The inverse function of F(J(m)), i.e. J(m)(c)(T, B-a, (B) over dot(a)), is in excellent agreement with the experimental results of J(m)(T, B-a, (B) over dot(a)). Hence in a range of temperatures and applied fields, the optimum temperature, current and field dependencies of activation energy can be ascertained without a priori assumption of their explicit forms. (C) 1998 Elsevier Science Ltd. All rights reserved.