Flux-line cutting in granular high-T-c and semi-reversible classical type-II superconductors

The magnetic responses of granular (NdBa2Cu3O7-x and YBa2Cu3O7-x) and monol ithic (PbIn) superconducting plates, cooled in a fixed magnetic field H-z p arallel to their plane and, later, subjected to cycles of a transverse magn etic field H-y with an amplitude H-y,H-max > H-z, are investigated both exp erimentally and theoretically. Magnetization curves, generated as H-y with H-z constant applied and of the order of the full penetration field H-p, ar e interpreted by employing two competing models (the double critical-state model and the two-velocity hydrodynamic model) for describing flux-line cut ting effects on the magnetic behaviour of superconductors. Both models qual itatively and semi-quantitatively reproduce the experimental curves. Unlike the double critical-state model, the two-velocity hydrodynamic approach pr edicts the appearance of zones with homogeneous magnitude of the magnetic i nduction B at relatively small values of H-y as \H-y\ is increased. However the effect of these zones is not appreciable since they disappear when \H- y\ reaches a sufficiently large value: \H-y\ greater than or similar to H-z approximate to H-p.