Observation of vortex expulsion in mesoscopic superconducting disks

We have studied vortex expulsion processes in a superconducting disk with a multi-terminal Hall sensor. Various combinations of these terminals enabled us to obtain an angular dependence of magnetization in the disk. The resolution of π/4 allowed us to identify three vortices. With a decrease in magnetic fields, vortices were expelled one by one from the different edges. After each expulsion the residual vortices were reconfigured in a complicated way. Their equilibrium positions changed with lowering temperatures. These results are interpreted in terms of repulsively interacting particles in the confinement and the pinning potential. The latter potential is found to be important at low temperatures.