Activation energy of Bi₂Sr₂Ca₁-_xEr_x Cu₂O_8+d epitaxial thin films

The scaling behavior of the effective activation energy U (T,H) of epitaxial oriented Bi₂Sr₂Ca₁-_xEr_xCu ₂O_8+d thin films with 0 ≤ x ≤ 0.10 has been studied as function of temperature and magnetic field. It has been found that the activation energy scales as U (H,T) = U_o (1-t)^m Hⁿ with exponent m = 1.20±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.