Study of superconducting systems using scanning Hall probe microscopy

Scanning Hall probe microscopy (SHM) is an important new magnetic imaging technique that allows direct spatial measurement of magnetic structures with high magnetic sensitivity and spatial resolution. This combination of features has allowed us to study aspect of two distinct superconducting systems that would not be possible using other methods.;An array of isolated type I superconducting rings at an applied flux of ;Spatial images from the SHM give new insights into the problem of how magnetic fields penetrate the interior of type II superconductors. We observe vortices driven into superconducting samples with two different geometries by ramping an external magnetic field. In a 50 ;Field penetration into a 100-;We have also observed vortex motion due to transport currents in these niobium strips. When the critical current is exceeded, certain regions of the sample exhibit field fluctuations on time scales orders of magnitude longer than the travel times of single vortices. Such fluctuations indicate patterns of possible channels of irregular vortex motion that become more uniform with increasing current.