Activation energy of Bi2Sr2Ca(Cu1-xFex)(2)O8+d thin films

The scaling behavior of the effective activation energy U(T, H) of epitaxia l c-axis oriented Bi2Sr2Ca(Cu1-xFex)(2)O8+d thin films with 0 < x less than or equal to 0.02 has been studied as a function of temperature and magneti c field. It has been found that the activation energy scales as U(H, T) = U -0 (1 - t)H-m(n) with exponent m = 1.15 +/- 0.03 and n = - 1/2. The field a nd temperature dependence of the activation energy, as well as its overall magnitude is consistent with a model in which U(T, H) arises from plastic d eformations of viscous flux liquid above the vortex-glass transition temper ature.