| Popis: |
The dynamic magnetic hysteresis loops m(T, B a , B a ) of an epitaxial Tl2Ba2CaCu2O8 superconducting thin film are measured at various field sweep rates B a and at temperatures ranging from (1/2)Tc to (4/5)Tc. The magnetization current densities J m (T, B a , B 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(Jm) and Bγa are uniquely determined for a range of temperatures and applied fields. The inverse function of F(Jm), i.e. J c m (T, B a , B a ) , is in excellent agreement with the experimental results of J m (T, B a , B 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. |
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