Barkhausen-like conductance noise in polycrystalline high-T_c superconductors immersed in a slowly varying magnetic field

Analysis of the resistive transition of a polycrystalline YBCO specimen produced by a low-frequency ac magnetic field reveals the presence of a large conductance noise signal that is repetitive over subsequent magnetization cycles until a large magnetic perturbation is applied. It is shown that the noise arises from avalanche effects produced by the simultaneous resistive transition of large groups of weak links. Owing to its repeatability, the noise signal may be considered as sort of signature of the weak-link critical-current distribution, making it an interesting tool for the study of high-T_c ceramic superconductors, as reported measurements of the noise hysteresis show.