Vortex Confinement in S/F heterostructures

Low temperature scanning tunneling microscopy and magnetic force microscopy have been used to directly visualize the superconducting vortex behavior in hybrid structures consisting of striped ferromagnetic materials (such as Py or Co/Pd) and conventional superconductors (such as Nb or Pb). We observe that strong confinement potential profoundly affects the vortex spatial distribution eventually leading to vortex cluster formation. High resolution scanning tunneling microscopy has been used to obtain detailed information of the local electronic density of states outside and inside the vortex clusters.