The magnetism of nickel monolayers

Nickel allows to study the largest variety of phenomena in the magnetism of UHV ultrathin films. The low critical temperature of approximate to 630 K for the bulk favors experiments from 0 K to above T-c and from one monolayer to infinite thick films. The thickness dependence of T-c (d) for the (001) and the (111) orientation is compared. Susceptibility measurements in UHV are presented, and from chi(max) the film geometry can be deduced. Ferromagnetic resonance measures the second- and fourth-order anisotropy constants. These give a clear understanding of when and how the reorientation transition from the inplane to the perpendicular orientation occurs and its nature. Magnetic resonance and circular X-ray dichroism measure the spin and orbital parts of the magnetic moment mu, its anisotropy Delta mu, and the 3d and 4sp contributions. Finally, we show how a 4 Monolayer (ML) Ni (001) film can be transformed into NiO by controlled oxygen dosage and thermal treatment.