EFFECT OF MICROSTRUCTURAL CHANGES ON THERMALLY ACTIVATED FLUX-CREEP BEHAVIOR IN THE BI-SR-CA-CU-O SYSTEM

We measured magnetic relaxation for the zero-field-cooled magnetization of liquid-quenched Bi-Sr-Ca-Cu-O samples with various microstructures at an applied field of 1 kOe. We found that a large amount of crystal defects observed in the sample matrix greatly increase the pinning strength and, in turn, enhance the flux-creep behavior. The relaxation rate peaks at 14 K and drops to zero near 60 K. The increased activation energy in our crystallized samples is attributed to strong pinning caused by a high density of precipitates and lattice stacking faults. © 1990 The American Physical Society.