Anomalous vortex properties of superconductor(Nb)/ferromagnet(Co) multilayers

Abstract We have measured magnetization on RF-sputtered superconductor(Nb)/ferromagnet(Co) multilayers to investigate the influence of magnetism on vortex properties. Under perpendicular applied fields, we observed a maximum of magnetization at low fields whose position is dependent on both temperature and layer thickness. These observations imply vortex–lattice transitions associated with vortex pinning by Co magnetic moments.