Extended Rate Equation for Flux Motion in High-T_c Superconductors

The rate equation for flux motion in high- T_c superconductors is extended to take the contribution of field sweep into account in this work. It is shown that the time and field sweep rate (H) dependence of magnetization are equivalent approaches to the study of flux creep properties in high- T_c superconductors. The agreement of the effective activation energy U_eff (J) extracted from the time relaxation and that from magnetic hysteresis loops measurements on a melt-textured YBa₂Cu₃O_6+x sample supports this extended rate equation for flux motion in high temperature superconductors.