533 research outputs found
Hierarchically Porous Gd3+-Doped CeO2 Nanostructures for the Remarkable Enhancement of Optical and Magnetic Properties
Rare earth ion-doped CeO2 has attracted more and more attention because of its special electrical, optical, magnetic, or catalytic properties. In this paper, a facile electrochemical deposition route was reported for the direct growth of the porous Gd-doped CeO2. The formation process of Gd-doped CeO2 composites was investigated. The obtained deposits were characterized by SEM, EDS, XRD, and XPS. The porous Gd3+- doped CeO2 (10 at% Gd) displays a typical type I adsorption isotherm and yields a large specific surface area of 135 m2/g. As Gd3+ ions were doped into CeO2 lattice, the absorption spectrum of Gd3+-doped CeO2 nanocrystals exhibited a red shift compared with porous CeO2 nanocrystals and bulk CeO2, and the luminescence of Gd3+-doped CeO2 deposits was remarkably enhanced due to the presence of more oxygen vacancies. In addition, the strong magnetic properties of Gd-doped CeO2 (10 at% Gd) were observed, which may be caused by Gd3+ ions or more oxygen defects in deposits. In addition, the catalytic activity of porous Gd-doped CeO2 toward CO oxidation was studied
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Technique for bulk Fermiology by photoemission applied to layered ruthenates
We report the Fermi surfaces of the superconductor Sr2RuO4 and the
non-superconductor Sr1.8Ca0.2RuO4 probed by bulk-sensitive high-energy
angle-resolved photoemission. It is found that there is one square-shaped
hole-like, one square-shaped electron-like and one circle-shaped electron-like
Fermi surface in both compounds. These results provide direct evidence for
nesting instability giving rise to magnetic fluctuations. Our study clarifies
that the electron correlation effects are changed with composition depending on
the individual band.Comment: 5 pages, 3 figures including 2 color figure
Morphologies of three-dimensional shear bands in granular media
We present numerical results on spontaneous symmetry breaking strain
localization in axisymmetric triaxial shear tests of granular materials. We
simulated shear band formation using three-dimensional Distinct Element Method
with spherical particles. We demonstrate that the local shear intensity, the
angular velocity of the grains, the coordination number, and the local void
ratio are correlated and any of them can be used to identify shear bands,
however the latter two are less sensitive. The calculated shear band
morphologies are in good agreement with those found experimentally. We show
that boundary conditions play an important role. We discuss the formation
mechanism of shear bands in the light of our observations and compare the
results with experiments. At large strains, with enforced symmetry, we found
strain hardening.Comment: 6 pages 5 figures, low resolution figures
Variation of strong correlation effects in A-site ordered perovskites CaCu3Ti4-xRuxO12: Photoemission and inverse photoemission studies
We have systematically studied the strong correlation effects in A-site
ordered perovskites CaCu3Ti4-xRuxO12 (x = 0, 1, 3.5, 4) by using photoemission
and inverse photoemission spectroscopies. In x = 0, 1, 3.5, the peak positions
of the strongly correlated Cu 3d states around -3.8 eV and Ti 3d states around
3.6 eV little change. On the other hand, in x = 4, the Cu 3d states is observed
around -2.5 eV. These indicate that Ti plays an important role to retain the
strong correlation effects. In addition, the multiplet structures of Cu 3d
final states from -8 to -15 eV become weak as Ru increases, indicating the
reduction of the localized characters of Cu 3d states. At the Fermi level, we
observe the absence of spectral weight in x = 0, 1 and the development of Ru 4d
in-gap states between the Cu 3d and Ti 3d peaks in x = 3.5, 4, which give rise
to the metal-insulator transition between x = 1 and x = 3.5.Comment: 12 pages, 3 figure
High-energy photoemission on Fe3O4: Small polaron physics and the Verwey transition
We have studied the electronic structure and charge ordering (Verwey)
transition of magnetite (Fe3O4) by soft x-ray photoemission. Due to the
enhanced probing depth and the use of different surface preparations we are
able to distinguish surface and volume effects in the spectra. The pseudogap
behavior of the intrinsic spectra and its temperature dependence give evidence
for the existence of strongly bound small polarons consistent with both dc and
optical conductivity. Together with other recent structural and theoretical
results our findings support a picture in which the Verwey transition contains
elements of a cooperative Jahn-Teller effect, stabilized by local Coulomb
interaction
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