Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

TT: Tiefe Temperaturen

TT 12: Fachsymposium 2: Künstliche Pinning Zentren

TT 12.1: Hauptvortrag

Dienstag, 27. März 2001, 14:30–15:00, J

Flux Confinement Effects in Nanostructured Superconductors — •V. V. Moshchalkov — Laboratory for Solid State Physics and Magnetism, KU Leuven, Celestijnenlaan 200 D, 3001 Leuven, Belgium

Flux confinement phenomena have been studied in individual superconducting nanoplaquettes and their huge arrays (films with nanoengineered periodic pinning arrays (PPA)). In individual nanoplaquettes of different form (loops, discs, triangles, and squares) the superconducting critical temperature was measured resistively and also calculated from the linearized Ginzburg-Landau equations. Novel symmetry-consistent vortex patterns have been identified for triangles and squares. To keep the imposed symmetry, vortex-antivortex pairs can be spontaneously formed. For example, in an equilateral triangle with two flux quanta, an antivortex is formed in the center and three vortices sit in the corners (for details see Nature 408, 833 (2000)). In multiloops and antidot clusters the spontaneous changes of connectivity are investigated. In films with PPA (lattices of antidots or magnetic dots) pronounced peaks at integer and rational fields have been revealed in magnetization and transport measurements. The peaks are attributed to certain stable vortex configurations. These configurations can be directly visualised by using different vortex imaging techniques: magnetic decoration, Lorentz- and scanning Hall probe microscopy. The combination of these local techniques with the bulk probes allows to identify correctly all relevant patterns (multiquanta and composite vortex lattices, interpenetrating sublattices of strongly and weakly pinned vortices, etc.) responsible for the strong enhancement of the critical current.