Vortex Lattices in High Temperature Superconducting Single Crystals and Thin Films by Bitter Magnetic Decoration: Order/Disorder Analysis

R.F. LUCCAS; T. PUIG; X. GRANADOS; X. OBRADORS; Y. FASANO; F. DE LA CRUZ; G. NIEVA

Rhodas (Grecia)

Conferencia; 5th International Conf. on Vortex Matter In Nanostructures Superconductors; 2007

Bitter Magnetic Decoration is one of the best techniques for the visualization of the vortex lattice in large areas of superconducting materials. The analysis of periodicity, order/disorder and symmetry of the lattice through image processing allows us to study the vortices behaviour in the lattice as well as their interaction with material's defects, naturally or artificially made. We have implemented a Bitter Magnetic Decoration system where special emphasis on the iron evaporation process has been considered by automatically controlling the filament current. We have worked at 4.2 K in a range of magnetic fields higher than 10 G. Results on BiSCCO-2212 and YBCO-123 single crystals as well as on YBCO-123 thin films grown by laser ablation are presented. Our results show a typical hexagonal ordered lattice (Abrikosov lattice) for BiSCCO and YBCO single crystals. However, in YBCO thin films a disordered lattice is obtained suggesting the appearance of a vortex glass regime associated to the strong pinning capability of these thin films. Additional analysis of the vortex positions distribution evidences that the interaction between vortices within the lattice of the single crystal is preserved at distances up to nine lattice parameters at least. Instead, in the case of YBCO thin film, we observe a disordered lattice where the distribution of vortices presents a one lattice parameter separation, between two neighboring vortices, in agreement with the value of the applied magnetic field.