OBSERVATION OF THE INTERACTION OF VORTICES WITH DISLOCATIONS IN A NB SUPERCONDUCTOR BY A CRYO-LORENTZ EM

The arrangement of quantized magnetic flux lines (vortices) in a Nb su perconductor was observed in different magnetic fields up to 200 Gauss by a cryo-Lorentz electron microscope. The interaction of vortices wi th dislocations in the specimen could directly be clarified. Edge-on d islocations, having been parallel to the vortex core, were identified to pin individual vortices effectively at magnetic fields below 100 Ga uss. In higher magnetic fields the formation of a regular hexagonal vo rtex lattice started preferentially at in-plane dislocations. At 200 G auss the Abrikosov vortex lattice was formed almost completely and it revealed domains of vortex lattice with slightly different orientation s. The dislocations were observed in the centre part of the domains, s howing their important role on the formation of the vortex lattice.