Flux creep and pinning potential distribution in zone-melted YBa2Cu3Ox

Magnetic relaxation data have been taken on zone-melted and sintered YBa₂Cu₃O_x samples over wide temperature and magnetic field ranges. We have found that magnetic relaxation varies greatly in the samples with different microstructures and crystallographic orientations. Flux-creep rates have been found to be reduced in the zone-melted samples owing to large amounts of intragranular crystal defects such as edge dislocations and stacking faults. An important flux-pinning behavior related to the pinning potential distributions has been observed in the samples. The relationship between microstructural orientation and pinning potential distributions in YBa₂Cu₃O_x is discussed.