ACTIVATION ENERGY OFBi2Sr2Ca(Cu1-xFex)2O8+dTHIN FILMS

The scaling behavior of the effective activation energy U(T,H) of epitaxial c-axis oriented Bi2Sr2Ca(Cu1-xFex)2O8+d thin films with 0 ≤ x ≤ 0.02 has been studied as a function of temperature and magnetic field. It has been found that the activation energy scales as U(H,T) = U0(1 - t)mHn with exponent m = 1.15 ± 0.03 and n = -1/2. The field and 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 deformations of viscous flux liquid above the vortex-glass transition temperature.