Irreversible matching effects in homogeneous and layered superconducting films

Numerical simulation is used to study the vortex dynamics in thin supercond ucting homogeneous films and multilayers. The films are assumed to have thi ckness less than or equal to the penetration depth and subjected to a paral lel magnetic field. The structure of the multilayers is treated as a period ic pinning potential. We use Langevin dynamics and London theory to calcula te the vortex configurations when the external field is increased from zero to a maximum value and turned back to zero. The results show that the vort ex lattice consists of parallel linear chains of vortices and goes through transitions from n to n + 1 chains in particular values of the increasing f ield. The strong surface effects yield an irreversible magnetization curve even for the homogeneous films. Moreover, the pinning structure of the mult ilayers presents only small influence on the vortex lattice. (C) 2001 Elsev ier Science B.V. All rights reserved.