We investigate the dependence of the magnetic anisotropy and magnetic moments in surface-supported nanostructures on local atomic coordination, structure size, substrate material and orientation, and the interaction with molecular ligands. Since the relevant length scale of the exchange interaction is only a few atomic distances, magnetic materials must be engineered down to the sub-nanometer scale to make coordination and size effects observable. The synthesis of surface-supported nanostructures with atomic precision and unprecedented complexity is therefore an important part of our program. We study model nanostructures locally with low-temperature scanning probe microscopy and spectroscopy. Integral magnetic behavior is studied over large surface areas with magneto-optical Kerr effect as well as X-ray magnetic dichroism measurements. The combination of local and integral methods allows for a comprehensive characterization of the correlation between structure, the electronic properties and the magnetism.

Sub-Nanostructures

We are able to construct model nanostructures on crystalline surfaces, almost atom-by-atom. The comparative investigation of such structures with local and integral methods reveals the influence of the local atomic arrangement on the magnetic moments or the magnetic anisotropy. The results help us to develop a fundamental understanding of the magnetism in nanostructures, which could be useful to engineer magnetism by structural design.

 

Two-Dimensional Systems

On atomically thin metal films we study interface effects, spin reorientation transitions and micromagnetic phenomena. We are particularly interested in the dependence of the magnetism on film morphology, epitaxial strain, interface properties, adsorbate coverage, temperature and other perturbations.

 

 

Clusters on Surfaces

Clusters are at the crossover between monatomic aggregates and bulk materials and have electronic and magnetic properties distinctive from both. We fabricate nanometer-size clusters on surfaces to study size effects in the magnetic moments or the magnetic anisotropy. We expend particular effort on developing fabrication strategies for self-assembled patterned media, which – if applied in magnetic recording – would allow for unprecedented bit densities.