EXPERIMENTAL STUDY OF LOCAL FLUX CREEP ON A CYLINDRICAL MELTING-TEXTURED GROWN YBa 2 Cu 3 O 7-δ SAMPLE AT APPLIED FIELDS

Using semiconductor Hall probes,we studied the local flux creep on a cylindrical melting-textured grown YBa 2 Cu 3 O 7-δ sample at liquid nitrogen temperature and low applied field.The measurements on the top surface of the sample show that the local flux creep fits well the logarithmic time dependence in both the field-on and field-off cases.The obtained activation energy U 0 in the field-on case is greater than the field-off one.The local magnetization was almost changing with the applied field synchronously in the measurement of magnetic hysteresis loops.The field was almost identical at a fixed local point under various sweep ratios of the applied field.The results imply that besides the side surface the applied field penetrates into the upper and lower surfaces to a certain extent too.The disparity in U 0 results from the difference of the angle between the flux line and the ab plane.This study also shows that the measurement of flux creep at the low field has a potential to become a simple and effective method to investigate the pinning property in large size samples.