1,765 research outputs found
Electronic and magnetic properties of the kagome systems YBaCo4O7 and YBaCo3MO7 (M=Al, Fe)
We present a combined experimental and theoretical x-ray absorption
spectroscopy (XAS) study of the new class of cobaltates YBaCo4O7 and YBaCo3MO7
(M= Al, Fe). The focus is on the local electronic and magnetic properties of
the transition metal ions in these geometrically frustrated kagome compounds.
For the mixed valence cobaltate YBaCo4O7, both the Co2+ and Co3+ are found to
be in the high spin state. The stability of these high spin states in
tetrahedral coordination is compared with those in the more studied case of
octahedral coordination. For the new compound YBaCo3FeO7, we find exclusively
Co2+ and Fe3+ as charge states
Correlation effects in CaCu3Ru4O12
We have investigated the electronic structure of CaCu3Ru4O12 and LaCu3Ru4O12
using soft x-ray photoelectron and absorption spectroscopy together with band
structure and cluster configuration interaction calculations. We found the Cu
to be in a robust divalent ionic state while the Ru is more itinerant in
character and stabilizes the metallic state. Substitution of Ca by La
predominantly affects the Ru states. We observed strong correlation effects in
the Cu 3d states affecting the valence band line shape considerably. Using
resonant photoelectron spectroscopy at the Cu L3 edge we were able to unveil
the position of the Zhang-Rice singlet states in the one-electron removal
spectrum of the Cu with respect to the Ru-derived metallic bands in the
vicinity of the chemical potential
Home country effects of offshoring. A critical survey on empirical literature.
The International fragmentation of production processes is of rising importance. One part of this fragmentation involves the relocation of a production process from a home- to a new host country. This literature survey deals with the effects of such relocations on the home country. First of all, we try to conceptualize the terms and definitions most frequently used in this context which are "outsourcing", "offshore outsourcing" and "offshoring". Despite the fact that there is little textual documentation dealing directly with the phenomena of offshoring and offshore outsourcing we try to give an overview of possible empirical literature to which one can regard to. Including FDI literature we try to cover empirical literature which can provide helpful insight on the effects of a relocation to foreign countries on the home country in connection with wages, skill upgrading, prices, profits, taxes and unions. (author's abstract)Series: Discussion Papers SFB International Tax Coordinatio
Plasma from Volunteers Breathing Helium Reduces Hypoxia-Induced Cell Damage in Human Endothelial Cells-Mechanisms of Remote Protection Against Hypoxia by Helium.
PurposeRemote ischemic preconditioning protects peripheral organs against prolonged ischemia/reperfusion injury via circulating protective factors. Preconditioning with helium protected healthy volunteers against postischemic endothelial dysfunction. We investigated whether plasma from helium-treated volunteers can protect human umbilical vein endothelial cells (HUVECs) against hypoxia in vitro through release of circulating of factors.MethodsHealthy male volunteers inhaled heliox (79% helium, 21% oxygen) or air for 30 min. Plasma was collected at baseline, directly after inhalation, 6 h and 24 h after start of the experiment. HUVECs were incubated with either 5% or 10% of the plasma for 1 or 2 h and subjected to enzymatically induced hypoxia. Cell damage was measured by LDH content. Furthermore, caveolin 1 (Cav-1), hypoxia-inducible factor (HIF1α), extracellular signal-regulated kinase (ERK)1/2, signal transducer and activator of transcription (STAT3) and endothelial nitric oxide synthase (eNOS) were determined.ResultsPrehypoxic exposure to 10% plasma obtained 6 h after helium inhalation decreased hypoxia-induced cell damage in HUVEC. Cav-1 knockdown in HUVEC abolished this effect.ConclusionsPlasma of healthy volunteers breathing helium protects HUVEC against hypoxic cell damage, possibly involving circulating Cav-1
Spin blockade, orbital occupation and charge ordering in La_(1.5)Sr_(0.5)CoO4
Using Co-L_(2,3) and O-K x-ray absorption spectroscopy, we reveal that the
charge ordering in La_(1.5)Sr_(0.5)CoO4 involves high spin (S=3/2) Co^2+ and
low spin (S=0) Co^3+ ions. This provides evidence for the spin blockade
phenomenon as a source for the extremely insulating nature of the
La_(2-x)Sr_(x)CoO4 series. The associated e_g^2 and e_g^0 orbital occupation
accounts for the large contrast in the Co-O bond lengths, and in turn, the high
charge ordering temperature. Yet, the low magnetic ordering temperature is
naturally explained by the presence of the non-magnetic (S=0) Co^3+ ions. From
the identification of the bands we infer that La_(1.5)Sr_(0.5)CoO4 is a narrow
band material.Comment: 5 pages, 3 figure
Orbital order in La0.5Sr1.5MnO4: beyond a common local Jahn-Teller picture
The standard way to find the orbital occupation of Jahn-Teller (JT) ions is
to use structural data, with the assumption of a one-to-one correspondence
between the orbital occupation and the associated JT distortion, e.g. in O6
octahedron. We show, however, that this approach in principle does not work for
layered systems. Specifically, using the layered manganite La0.5Sr1.5MnO4 as an
example, we found from our x-ray absorption measurements and theoretical
calculations, that the type of orbital ordering strongly contradicts the
standard local distortion approach for the Mn3+O6 octahedra, and that the
generally ignored long-range crystal field effect and anisotropic hopping
integrals are actually crucial to determine the orbital occupation. Our
findings may open a pathway to control of the orbital state in multilayer
systems and thus of their physical properties.Comment: 4+ pages, 4 figure
Epitaxial and layer-by-layer growth of EuO thin films on yttria-stabilized cubic zirconia (001) using MBE distillation
We have succeeded in growing epitaxial and highly stoichiometric films of EuO
on yttria-stabilized cubic zirconia (YSZ) (001). The use of the Eu-distillation
process during the molecular beam epitaxy assisted growth enables the
consistent achievement of stoichiometry. We have also succeeded in growing the
films in a layer-by-layer fashion by fine tuning the Eu vs. oxygen deposition
rates. The initial stages of growth involve the limited supply of oxygen from
the YSZ substrate, but the EuO stoichiometry can still be well maintained. The
films grown were sufficiently smooth so that the capping with a thin layer of
aluminum was leak tight and enabled ex situ experiments free from trivalent Eu
species. The findings were used to obtain recipes for better epitaxial growth
of EuO on MgO (001).Comment: 10 pages, 15 figure
Orbital occupation and magnetic moments of tetrahedrally coordinated iron in CaBaFe4O7
CaBaFe4O7 is a mixed-valent transition metal oxide having both Fe2+ and Fe3+
ions in tetrahedral coordination. Here we characterize its magnetic properties
by magnetization measurements and investigate its local electronic structure
using soft x-ray absorption spectroscopy at the Fe L2,3 edges, in combination
with multiplet cluster and spin-resolved band structure calculations. We found
that the Fe2+ ion in the unusual tetrahedral coordination is Jahn-Teller active
with the high-spin e^2 (up) t2^3 (up) e^1 (down) configuration having a
x^2-y^2-like electron for the minority spin. We deduce that there is an
appreciable orbital moment of about L_z=0.36 caused by multiplet interactions,
thereby explaining the observed magnetic anisotropy. CaBaFe4O7, a member of the
'114' oxide family, offers new opportunities to explore charge, orbital and
spin physics in transition metal oxides
Electronic signature of the vacancy ordering in NbO (Nb3O3)
We investigated the electronic structure of the vacancy-ordered 4d-transition
metal monoxide NbO (Nb3O3) using angle-integrated soft- and hard-x-ray
photoelectron spectroscopy as well as ultra-violet angle-resolved photoelectron
spectroscopy. We found that density-functional-based band structure
calculations can describe the spectral features accurately provided that
self-interaction effects are taken into account. In the angle-resolved spectra
we were able to identify the so-called vacancy band that characterizes the
ordering of the vacancies. This together with the band structure results
indicates the important role of the very large inter-Nb-4d hybridization for
the formation of the ordered vacancies and the high thermal stability of the
ordered structure of niobium monoxide
- …