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

The magnetic properties in NdBCO single crystal fabricated by flux growing method in controlled oxygen atmosphere have been investigated using both SQUID magnetometer and magneto-optical (M-O) technique before and after heavy ions irradiation. An external magnetic field was applied parallel to the sample c-axis up to 7 T at different temperatures. Critical current densities 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 equipped 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 strongly affects the magnetic behaviour. The direct and detailed visualization of the field behaviour provided by magneto optical images allows a more precise understanding of the magnetization loops.