  Magnetic domain structure and spin-dependent reflectivity measurements on
cobalt thin films intercalated at the graphene / Ir(111) interface are
investigated using spin-polarised low-energy electron microscopy. We find that
graphene-covered cobalt films have surprising magnetic properties. Vectorial
imaging of magnetic domains reveals an unusually gradual thickness-dependent
spin reorientation transition, in which magnetisation rotates from
out-of-the-film plane to the in-plane direction by less than 10$^\circ$ per
cobalt monolayer. During this transition, cobalt films have a meandering spin
texture, characterised by a complex, three-dimensional, wavy magnetisation
pattern. In addition, spectroscopy measurements indicate that the electronic
band structure of the unoccupied states is essentially spin-independent already
a few electron-Volts above the vacuum level. These properties strikingly differ
from those of pristine cobalt films and could open new prospects in surface
magnetism.
