Anisotropic phase diagram at higher temperature for Tl₂Ba₂CaCu₂O₈ thin film

By measuring the temperature dependence of the magnetoresistivity of Tl₂Ba₂CaCu₂O₈ thin films, two superconducting transitions were observed for field orientations in the H⊥ab- and H∥ab-planes. The transition at the high temperature (T_ch) corresponds to a steep peak in the derivative of the effective activation energy and shifts very moderately with increasing magnetic field. The transition is in good agreement with the value of the upper critical field derived from critical fluctuation theory. Meanwhile, the transition at low temperature (T_cl) was associated with the Josephson coupling and strong intrinsic pinning for the two field orientations, respectively. This is consistent with the different magnetic field dependence of the activation energy calculated from the experimental data between T_ch and T_cl.