Local magnetic measurement of strong pinning by columnar defects

Abstract Local magnetic measurements by Hall-sensor arrays are used to study flux penetration and trapping in heavy ion irradiated YBCO:123 crystals. From the Bean-like flux profiles we obtain loops of the field gradient dB z /dx vs local induction B z , which show an asymmetry between the flux penetration and exit processes. The asymmetry is related to a sudden acceleration of the relaxation at some characteristic value of the local induction during flux penetration only.