  We present a first-principles study of the surface magnetism induced by Cr,
Mn, Fe and Co adatoms on the (111) surfaces of Rh, Pd, Ag, Ir, Pt and Au. We
first describe how the different contributions to the surface magnetism enter
the magnetic stray field, with special attention paid to the induced orbital
moments. Then we present results for the spin and orbital magnetic moments of
the adatoms, and for the induced surface spin and orbital magnetic moments, the
latter being further divided into atomic and inter-atomic contributions. We
investigate how the surface magnetism is determined by the chemical nature of
the elements involved, such as the filling of the magnetic d-orbitals of the
adatoms and the properties of the itinerant electrons at the surface (whether
they are sp- or d-like, and whether the spin-orbit interaction is relevant),
and how it is modified if the magnetic adatoms are brought together to form a
cluster, with Cr, Mn, Fe, and Co trimers on Pt(111) as an example. We also
explore the impact of computational approximations, such as the distance
between the adatom and the Pt(111) surface, or confinement effects due to the
finite thickness of the slab used to model it. Our discussion of the magnetic
stray field generated by a single adatom and its environment suggests a
possible way of disentangling the induced surface magnetism from the adatom
one, which could be feasible with scanning NV-center microscopy.
