Dip effect in ac susceptibility due to surface barrier with flux creep

[摘要] A model is proposed to describe the effect of surface barrier (SB) on ac susceptibility (ACS) and a different kind of dip effect (DE) in ACS is observed. Simulation based on this model with flux creep reveals two dips in ACS curve, one at temperature T-d(') in real part chi(') and the other at temperature T-d(') in imaginary part chi('). These two dips are different from the ones resulting from the peak effect in critical current density j(c), where the dips in chi(') and chi(') occur at the same temperature T-p. The DE is also characterized by a large chi(') and a large parallel tochi(')(T-d('))parallel to. The ACS curves for single crystals Bi2Sr2CaCu2O8 have been observed and compared with the DE in YBa2Cu3O7 samples, confirming the numerical results. It is also shown that when flux creep is absent only kinks appear in chi(') and chi(') for a sample with SB.

[发布日期] 2003-12-01

[关键词] HIGH-TEMPERATURE SUPERCONDUCTORS;II SUPERCONDUCTORS;TRANSPORT-PROPERTIES;MAGNETIC-RELAXATION;SINGLE-CRYSTALS;CRITICAL-STATE;VORTEX MATTER;FIELD;YBA2CU3O7-DELTA;BI2SR2CACU2O8