Magnetization relaxation in the flux-creep annealing regime across the second magnetization peak of disordered YBa2Cu3O7− crystals

Abstract The relaxation of the irreversible magnetization of disordered YBa 2 Cu 3 O 7− x crystals measured in the “flux-creep annealing” regime reveals that across the second magnetization peak (SMP) the barriers against flux motion remain finite at low current densities, which supports the existence of a crossover to a dissipation process involving the plastic deformation of the vortex system. In our experiments, the vortex creep process appears to be exclusively controlled by collective pinning barriers (diverging at low current densities) only below the onset of the SMP, where the vortex system is stable against dislocation formation. The (elastic) collective pinning barriers observed f…