  We have investigated the magnetism of the bare and graphene-covered (111)
surface of a Ni single crystal employing three different magnetic imaging
techniques and ab initio calculations, covering length scales from the
nanometer regime up to several millimeters. With low temperature spinpolarized
scanning tunneling microscopy (SP-STM) we find domain walls with widths of 60 -
90 nm, which can be moved by small perpendicular magnetic fields. Spin contrast
is also achieved on the graphene-covered surface, which means that the electron
density in the vacuum above graphene is substantially spin-polarized. In
accordance with our ab initio calculations we find an enhanced atomic
corrugation with respect to the bare surface, due to the presence of the carbon
pz orbitals and as a result of the quenching of Ni surface states. The latter
also leads to an inversion of spinpolarization with respect to the pristine
surface. Room temperature Kerr microscopy shows a stripe like domain pattern
with stripe widths of 3 - 6 {\mu}m. Applying in-plane-fields, domain walls
start to move at about 13 mT and a single domain state is achieved at 140 mT.
Via scanning electron microscopy with polarization analysis (SEMPA) a second
type of modulation within the stripes is found and identified as 330 nm wide
V-lines. Qualitatively, the observed surface domain pattern originates from
bulk domains and their quasi-domain branching is driven by stray field
reduction.
