Direct observation of the interaction between vortices and dislocations insuperconducting crystals by a cryo-Lorentz EM (interaction between vortices and dislocations)

Quantized magnetic nux lines (vortices) in a Nb foil were directly observed in different magnetic fields up to 200 G by a cryo-lorentz electron micros cope. The interaction of vortices with dislocations in the specimen was exa mined and clarified; edge-on dislocations weakly pin individual vortices at magnetic fields below 100 G, In higher magnetic fields the formation of a regular hexagonal vortex lattice started preferentially at in-plane disloca tions. At 200 G the Abrikosov vortex lattice was formed with small domains, whose centre included the dislocations, showing their important role on th e formation of the vortex lattice. For a NbTi foil no clear image of vortic es could be seen, because the surface was rough due to the formation of fin e grains and precipitates.