Avalanche flux dynamics in the vortex state of type-II superconductors

We show that flux motion behavior in type II superconductors cab well be interpreted by the self-organized criticality theory. Based on a previous model developed by Tang, we derive various important relations for the dynamics of the vortex state including the time dependence of current density, j. We also experimentally demonstrate that flux entry at the initial stage in a zero-field -cooled relaxation experiment involves avalanches. The classical creep behavior, as treated by Anderson and Kim, is observed only in the small j regime.<>