Abstract
The dynamics of highly dilute vortex ensembles in thin films is investigated by low-field (5–90 Oe) ac susceptibility measurements of the dynamical relaxation rate Q. In a film with relatively weak pinning, flux bundling is found to be effective at all temperatures and down to the lowest fields. In a film with stronger pinning, single-vortex creep dominates only for and small bundle creep is fully developed for The behavior of highly separated vortices is hence surprisingly collective in Quantum creep is observed below 11 K, and at about 60 K the elastic vortex description breaks down as the importance of plastic creep gradually increases.
- Received 13 August 2001
DOI:https://doi.org/10.1103/PhysRevB.65.134525
©2002 American Physical Society