  Graphene is attractive for spintronics due to its long spin life time and
high mobility. So far only thick and polycrystalline slabs have been used as
ferromagnetic electrodes. We report the growth of flat, epitaxial ultrathin Co
films on graphene. These display perpendicular magnetic anisotropy in the
thickness range 0.5-1nm, which is confirmed by theory. PMA, epitaxy and
ultrathin thickness bring new perspectives for graphene-based spintronic
devices such as the zero-field control of an arbitrary magnetization direction,
band matching between electrodes and graphene, and interface effects such as
Rashba and electric field control of magnetism.
