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 630 K for the bulk favors experiments from 0 K to aboveT _c and from one monolayer to infinite thick films. The thickness dependence ofT _c (d) for the (001) and the (111) orientation is compared. Susceptibility measurements in UHV are presented, and from _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 in-plane 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 µ, its anisotropy µ, 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.Paper presented at the annual Spring Meeting of the Deutsche Physikalische Gesellschaft for Condensed- Matter Division, Berlin, Germany. 20–24 March, 1995