511 research outputs found
Li intercalation effects on magnetism in undoped and Co-doped anatase TiO
The effects of -type carrier doping by Li intercalation on magnetism in
undoped and Co-doped anatase TiO are investigated. We have found that doped
-type carriers in TiO are localized mainly at Ti sites near the
intercalated Li. With increasing the intercalation, local spins are realized at
Ti. In the case of Co-doped TiO, most of the added -type carriers fill
the Co 3 bands and the rest are localized at Ti. Therefore, Co magnetic
moment vanishes by Li intercalation to have a nonmagnetic ground state.Comment: 6 pages, 2 figures, to appear in a special issue of Physica B,
proceedings of the 2nd Hiroshima Workshop on Transport and Thermal Properties
of Advanced Materials (Aug. 2002; Hiroshima, Japan
Electronic structures of doped anatase : (M=Co, Mn, Fe, Ni)
We have investigated electronic structures of a room temperature diluted
magnetic semiconductor : Co-doped anatase . We have obtained the
half-metallic ground state in the local-spin-density approximation(LSDA) but
the insulating ground state in the LSDA++SO incorporating the spin-orbit
interaction. In the stoichiometric case, the low spin state of Co is realized
with the substantially large orbital moment. However, in the presence of oxygen
vacancies near Co, the spin state of Co becomes intermediate. The
ferromagnetisms in the metallic and insulating phases are accounted for by the
double-exchange-like and the superexchange mechanism, respectively. Further,
the magnetic ground states are obtained for Mn and Fe doped ,
while the paramagnetic ground state for Ni-doped .Comment: 5 pages, 4 figure
Charge and Orbital Ordering and Spin State Transition Driven by Structural Distortion in YBaCo_2O_5
We have investigated electronic structures of antiferromagnetic YBaCo_2O_5
using the local spin-density approximation (LSDA) + U method. The charge and
orbital ordered insulating ground state is correctly obtained with the strong
on-site Coulomb interaction. Co^{2+} and Co^{3+} ions are found to be in the
high spin (HS) and intermediate spin (IS) state, respectively. It is considered
that the tetragonal to orthorhombic structural transition is responsible for
the ordering phenomena and the spin states of Co ions. The large contribution
of the orbital moment to the total magnetic moment indicates that the
spin-orbit coupling is also important in YBaCo_2O_5.Comment: 4 pages including 4 figures, Submitted to Phys. Rev. Let
Satellite Estimates of the Direct Radiative Forcing of Biomass Burning Aerosols Over South America and Africa
Atmospheric aerosol particles, both natural and anthropogenic are important to the earth's radiative balance. Therefore it is important to provide adequate validation information on the spatial, temporal and radiative properties of aerosols. This will enable us to predict realistic global estimates of aerosol radiative effects more confidently. The current study utilizes 66 AVHRR LAC (Local Area Coverage) and coincident Earth Radiation Budget Experiment (ERBE) images to characterize the fires, smoke and radiative forcings of biomass burning aerosols over four major ecosystems of South America
Bogomol'nyi equations for solitons in Maxwell-Chern-Simons gauge theories with the magnetic moment interaction term
Without assuming rotational invariance, we derive Bogomol'nyi equations for
the solitons in the abelian Chern-Simons gauge theories with the anomalous
magnetic moment interaction. We also evaluate the number of zero modes around a
static soliton configuration.Comment: 9 pages, Revtex, SNUTP-94/6
Half-metallic antiferromagnets in thiospinels
We have theoretically designed the half-metallic (HM) antiferromagnets (AFMs)
in thiospinel systems, and , based on the electronic structure
studies in the local-spin-density approximation (LSDA). We have also explored
electronic and magnetic properties of parent spinel compounds of the above
systems; and are found to be HM
ferromagnets in their cubic spinel structures, while is a
ferrimagnetic insulator. We have discussed the feasibility of material
synthesis of HM-AFM thiospinel systems.Comment: 4 pages, 5 figure
On the inner Double-Resonance Raman scattering process in bilayer graphene
The dispersion of phonons and the electronic structure of graphene systems
can be obtained experimentally from the double-resonance (DR) Raman features by
varying the excitation laser energy. In a previous resonance Raman
investigation of graphene, the electronic structure was analyzed in the
framework of the Slonczewski-Weiss-McClure (SWM) model, considering the outer
DR process. In this work we analyze the data considering the inner DR process,
and obtain SWM parameters that are in better agreement with those obtained from
other experimental techniques. This result possibly shows that there is still a
fundamental open question concerning the double resonance process in graphene
systems.Comment: 5 pages, 3 figure
A Reverse Logistics Network Model for Handling Returned Products
58827Due to the emergence of e-commerce and the proliferation of liberal return policies, product returns have become daily routines for many companies. Considering the significant impact of product returns on the company’s bottom line, a growing number of
companies have attempted to streamline the reverse logistics process. Products are usually returned to initial collection points (ICPs) in small quantities and thus increase the unit shipping cost due to lack of freight discount opportunities. One way to address this issue is to aggregate the returned products into a larger shipment. However, such aggregation increases the
holding time at the ICP, which in turn increases the inventory carrying costs. Considering this logistics dilemma, the main objectives of this research are to minimize the total cost by determining the optimal location and collection period of holding time of ICPs; determining the optimal location of a centralized return centre; transforming the nonlinear objective function of the proposed model formulation by Min et al. (2006a) into a linear form; and conducting a sensitivity analysis to the model solutions according to varying parameters such as shipping volume. Existing models and solution procedures are too complicated to solve real-world problems. Through a series of computational experiments, we discovered that the linearization model obtained the optimal solution at a fraction of the time used by the traditional nonlinear model and solution procedure, as well as the ability to handle up to 150 customers as compared to 30 in the conventional nonlinear model. As such, the proposed linear model is
more suitable for actual industry applications than the existing models.S
Isotope effects and the charge gap formation in the charge ordered phase of colossal magnetoresistance manganites
Giant oxygen isotope effects observed in colossal magnetoresistance
manganites are investigated by employing the combined model of the double
exchange and interacting lattice polaron mechanism. We have shown that the
isotope effects on in the metallic phase and in the charge
ordered phase of manganites can be explained well in terms of the double
exchange and polaron narrowing factors with reasonable physical parameters.Comment: 5 pages, 3 figure
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