Flux-creep mechanism studied in extended windows for the HgBa 2Ca 2Cu 3O y superconductor

Abstract

Flux-creep mechanisms are examined by the current density J dependence of the effective barriers U( J), which were determined to be U(J) αJ −μ by three independent measurements i.e. AC susceptibility (ACS), magnetic relaxation ( M- t) and hysteresis loop ( M- H) for polycrystalline HgBa 2Ca 2Cu 3O y . It is found that, as J is increased, the U( J) of M- H decreases monotonically and gradually crosses over from μ = 0.43, which connects smoothly with the ACS one with J ≈ 10 2 A/cm 2, to the one with μ = 1.03, which just overlaps with the M- t one with J ≈ 10 6 A/cm 2. This result demonstrates the consistency of the data of the three methods and is considered to be evidence of a crossover between the CDW type and large bundle creep in the vortex-glass phase or collective-creep theories.