Study of flux dynamics in NdBCO single crystal before and after heavy ionsirradiation

The magnetic properties in NdBCO single crystal fabricated by flux growing method in controlled oxygen atmosphere have been investigated using both SQ UID magnetometer and magneto-optical (M-O) technique before and after heavy ions irradiation. An external magnetic field was applied parallel to the s ample c-axis up to 7 T at different temperatures. Critical current densitie s were obtained using the extended Bean model from the hysteresis loops as measured by SQUID. The M-O images were collected using a special facility e quipped with a superconductor magnet able to reach 8 T. The indicator film was produced in ISTEC. The M-O images were associated to the data obtained by analysing the magnetization curves. It was found that the irradiation st rongly affects the magnetic behaviour. The direct and detailed visualizatio n of the field behaviour provided by magneto optical images allows a more p recise understanding of the magnetization loops. (C) 2001 Elsevier Science B.V. All rights reserved.