"Magic" vicinal zinc oxide surfaces.

The structure of (0001) oriented ZnO single crystal surfaces is investigated by scanning tunneling microscopy. Depending on the preparation conditions, faceting of the crystals into large areas of {101¯4} surface orientation occurs. This restructuring of the surface is shown to be a consequence of dipole compensation and charge neutralization.

Microscopic nature of ferro- and antiferromagnetic interface coupling of uncompensated magnetic moments in exchange bias systems.

Exchange bias in layered CoO/Fe structures is investigated by x-ray resonant magnetic reflectivity (XRMR) measurements. Element-specific hysteresis loops are obtained from x-ray magnetic circular dichroism effects in the XRMR spectra. Evidence is provided for the existence of different types of uncompensated moments in the antiferromagnetic material.

Direct observation of exchange bias related uncompensated spins at the CoO/Cu interface.

Magnetization-induced optical second harmonic generation (MSHG) from the exchange-biased CoO/Cu-(X)/Fe multilayer shows the presence of pinned uncompensated spins at the CoO/Cu interface. For increasing Cu spacer thickness, the exchange bias measured via the hysteresis loop shift diminishes and disappears at X = 3.5 nm, while the MSHG signal still shows a strong magnetic contribution from the CoO interface.

Surface structure of ultrathin Fe films on Cu(001) revisited.

The structure and magnetism of ultrathin Fe films epitaxially grown on a Cu(001) surface are investigated by grazing scattering of fast H and He atoms or ions. By making use of a new variant of ion beam triangulation based on the detection of the number of emitted electrons, we obtain direct information on the structure of the film surface. We observe for room temperature growth a dominant and defined fcc-like structure.

Spin-glass-like behavior in CoO nanoparticles and the origin of exchange bias in layered CoO/ferromagnet structures.

The magnetic behavior of CoO nanoparticles and layered CoO/ferromagnetic (FM) structures has been investigated by magnetization and hysteresis loop measurements. In the amorphous CoO, a large uncompensation of spins is found that is closely related to spin-glass-like behavior below a freezing temperature T(F) approximately 215-220 K. The spin-glass-like phase may be described by the de Almeida-Thouless line for Ising spin systems.