A uniform description of irreversibility lines for various high- Tc superconductors

For a variety of high- T c superconducting systems with two-dimensional flux lattices the irreversibility lines can be described in a uniform manner by the theory of Matsushita which is based on a depinning mechanism caused by thermally activated flux creep. Two Bi-based and two Hg-based samples are selected for which in some cases the measurements are extended to magnetic fields up to 21 and 14 T, respectively. The theoretical description fits well in the whole temperature ranges between about 0.25 T c and T c. The activation energy for flux creep U 0 increases almost parabolically with decreasing temperature.