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It remains unclear why type-II antiferromagnetic order with a propagation vector along a trigonal axis and a tetragonal Jahn-Teller deformation coexist in a low-temperature phase of CoO. Nanocrystals generally have a lower magnetic transition temperature but crystal size reduction does not affect structural transition locally induced by a crystal field. On this basis, we investigated the magnetic and structural properties of CoO nanocrystals. Both transition temperatures were equally reduced in nanocrystals, which indicates that magnetic order triggers the tetragonal deformation. This observation is consistent with a model that the Jahn-Teller deformation is assisted by spin-orbit energy splitting of t2g electrons in the high-spin Co2+ ion, proposed by Kugel and Khomskii. [ABSTRACT FROM AUTHOR]

Local variation of frictional properties associated with adatoms of Sr and Cu with SrTiO[sub 3](100) surfaces was investigated by friction force microscopy. On the surfaces partially covered with Sr, strong friction was observed on Sr adlayers. In contrast, the areas covered with Cu showed weaker friction than the substrates. We found that a thick Cu layer became easily worn by scanning, so the stepped surface of the substrate appeared in the scanned area. Furthermore, inversion of the contrast in friction between the SrO and TiO[sub 2] terraces was observed in the same region during measurement. The origins of this friction behavior will be discussed in terms of the interaction between adsorbates and the substrate. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Friction force microscopy (FFM) was used to investigate local variation of frictional properties associated with adatoms of Strontium and copper with SrTiO3 (100) surfaces. Results indicate that FFM is a promising tool with which to investigate the initial state of thin film growth.

A two-dimensional electron gas interacting with an external periodic potential attracts attention as a designable artificial material to explore topological phases. Here, to introduce a periodic potential into a Shockley state, superstructures of CO molecules have been fabricated on a Cu(111) surface by atom manipulation with a low-temperature scanning tunneling microscope. Local electronic states have been investigated in relation to specific locations on the CO triangular lattice. All tunneling spectra of the lattice exhibit a reduction at the bottom energy of the surface-state band, which reflects absorption of surface-state electrons into the bulk. For an (8×8) CO structure, spectra measured at positions corresponding to two equivalent triangular sublattices of artificial graphene have different features near the Fermi level. This sublattice site dependence is not observed for a (6×6) structure. First-principles calculations for a (4×4) structure have reproduced the local density of states that depend on the sublattice sites. These results can be understood that coupling between the surface state and the bulk is strengthened via scattering by the adsorbates, and that the external periodic potential is perturbed by the second layer of the Cu(111) substrate. The periodicity of the external potential appears to be the key parameter which dominates the equivalence of pseudospin states in the artificial graphene. [ABSTRACT FROM AUTHOR]