We have investigated the correlation between morphology and magnetic anisotropy in nanostructured Co films on Cu(001). The formation of nanoscale ripples by ion erosion is found to deeply affect the magnetic properties of the Co film. A surface-type uniaxial magnetic anisotropy with easy axis parallel to the ripples is observed. The origin of the magnetic anisotropy has been identified with the modification of thermodynamic-step distribution induced by ripple formation. At higher ion doses, when Co ripples detach and crystalline nanowires form, a strong enhancement of the magnetic anisotropy due to magnetostatic contributions is observed.

Perovskite nickel oxides are of fundamental as well as technological interest because they show large resistance modulation associated with phase transition as a function of the temperature and chemical composition. Here, the effects of fluorine doping in perovskite nickelate NdNiO epitaxial thin films are investigated through a low-temperature reaction with polyvinylidene fluoride as the fluorine source. The fluorine content in the fluorinated NdNiOF films is controlled with precision by varying the reaction time. The fully fluorinated film (x ≈ 1) is highly insulating and has a bandgap of 2.1 eV, in contrast to NdNiO, which exhibits metallic transport properties. Hard X-ray photoelectron and soft X-ray absorption spectroscopies reveal the suppression of the density of states at the Fermi level as well as the reduction of nickel ions (valence state changes from +3 to +2) after fluorination, suggesting that the strong Coulombic repulsion in the Ni 3d orbitals associated with the fluorine substitution drives the metal-to-insulator transition. In addition, the resistivity of the fluorinated films recovers to the original value for NdNiO after annealing in an oxygen atmosphere. By application of the reversible fluorination process to transition-metal oxides, the search for resistance-switching materials could be accelerated.

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We have studied desorption of CO on a Pt-deposited highly oriented pyrolytic graphite (HOPG) surface by temperature programmed desorption of CO (CO-TPD), scanning tunneling microscope (STM), and He atom scattering (HAS). A desorption peak of CO at a significantly lower temperature of ∼270 K with a heating rate of 0.5 K/s is observed for Pt clusters on a flat terrace of HOPG. STM results indicate that the height of Pt clusters on the terraces of the HOPG surface is monatomic. It is concluded that the significant reduction in CO adsorption energy is due to a modified electronic structure as a result of the interface interaction between Pt clusters and the HOPG surface.

We have studied the electronic structure change of the Cu͑100͒ surface due to the lattice strain both experimentally and theoretically. In the experiments, the surface lattice is compressed by partial nitrogen adsorption. Detailed measurements were made using angle-resolved photoemission spectroscopy with synchrotron and He I radiations. We mainly focused on surface states at the d-band top and bottom, and also sp states ͑Shockley state͒ at X . The d-band bottom shifts toward higher binding energy, while the d-band top shifts toward the Fermi level. This is the direct evidence experimentally indicating the d-band broadening due to the lattice-constant reduction. The observation of the shift of the Shockley state beyond the Fermi level indicates the large electronic redistribution in the sp band. The changes in the electronic structures in the experiments are in good agreement with the results by first-principles calculations. The directions of the energy shifts due to the lattice contraction are well understood by considering the symmetry of the corresponding wave functions at each point of the surface Brillouin zone. An increase of the work function due to the lattice contraction is also discussed in terms of the first-principles calculations. This also implies the special redistribution of Cu 4sp electrons, which can significantly influence the chemical reaction on noble metals. Finally, the lattice-constant reduction is quantitatively estimated from the folding point shift of a surface state at the Brillouin-zone boundary.