406 research outputs found
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
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
Quantification of Methane Emissions from Indoor-Fed Fogera Dairy Cows Using Laser Methane Detector
Portable laser methane detectors (LMDs) may be an economical means of estimating CH4 emissions from ruminants. Here, we validated an LMD-based approach and then used that approach to evaluate CH4 emissions from indigenous dairy cows in a dryland area of Ethiopia. First, we validated our LMD-based approach in Simmental crossbred beef cattle (n = 2) housed in respiration chambers and fed either a high- or low-concentrate diet. We found that the exhaled air CH4 concentrations measured by LMD were linearly correlated with the CH4 emissions determined by infrared-absorption-based gas analyzer (r2 = 0.55). On the basis of these findings, we constructed an estimation equation to determine CH4 emissions (y, mg minâ1) from LMD CH4 concentrations (x, ppm m) as y = 0.4259x + 38.61. Next, we used our validated LMD approach to examine CH4 emissions in Fogera dairy cows grazed for 8 h dâ1 (GG, n = 4), fed indoors on natural-grassland hay (CG1, n = 4), or fed indoors on Napier-grass (Pennisetum purpureum) hay (CG2, n = 4). All the cows were supplemented with concentrate feed. Daily CH4 emissions did not differ among the three groups; however, a numerically greater milk yield was obtained from the CG2 cows than from the GG cows, suggesting that Napier-grass hay might be better than natural-grassland hay for indoor feeding. The CG1 cows had higher CH4 emissions per feed intake than the other groups, without significant increases in milk yield and body-weight gain, suggesting that natural-grassland hay cannot be recommended for indoor-fed cows. These findings demonstrate the potential of using LMDs to rapidly and economically evaluate feeding regimens for dairy cows in areas under financial constraint, while taking CH4 emissions into consideration
Vertical current induced domain wall motion in MgO-based magnetic tunnel junction with low current densities
Shifting electrically a magnetic domain wall (DW) by the spin transfer
mechanism is one of the future ways foreseen for the switching of spintronic
memories or registers. The classical geometries where the current is injected
in the plane of the magnetic layers suffer from a poor efficiency of the
intrinsic torques acting on the DWs. A way to circumvent this problem is to use
vertical current injection. In that case, theoretical calculations attribute
the microscopic origin of DW displacements to the out-of-plane (field-like)
spin transfer torque. Here we report experiments in which we controllably
displace a DW in the planar electrode of a magnetic tunnel junction by vertical
current injection. Our measurements confirm the major role of the out-of-plane
spin torque for DW motion, and allow to quantify this term precisely. The
involved current densities are about 100 times smaller than the one commonly
observed with in-plane currents. Step by step resistance switching of the
magnetic tunnel junction opens a new way for the realization of spintronic
memristive devices
Origin of "hot-spots" in the pseudogap regime of Nd(1.85)Ce(0.15)CuO(4): LDA+DMFT+Sigma_k study
Material specific electronic band structure of the electron-doped high-Tc
cuprate Nd(1.85)Ce(0.15)CuO(4) (NCCO) is calculated within the pseudo gap
regime, using the recently developed generalized LDA+DMFT+Sigma_k scheme.
LDA/DFT (density functional theory within local density approximation) provides
model parameters (hopping integral values, local Coulomb interaction strength)
for the one-band Hubbard model, which is solved by DMFT (dynamical mean-field
theory). To take into account pseudogap fluctuations LDA+DMFT is supplied with
"external" k-dependent self-energy Sigma_k, which describes interaction of
correlated conducting electrons with non-local Heisenberg-like
antiferromagnetic (AFM) spin fluctuations responsible for pseudo gap formation.
Within this LDA+DMFT+Sigma_k approach we demonstrate the formation of
pronounced "hot-spots" on the Fermi surface (FS) map in NCCO, opposite to our
recent calculations for Bi(2)Sr(2)CaCu(2)O(8-d) (Bi2212), which have produced
rather extended region of FS "destruction". There are several physical reasons
for this fact: (i) the "hot-spots" in NCCO are located closer to Brillouin zone
center; (ii) correlation length of AFM fluctuations \xi is larger for NCCO;
(iii) pseudogap potential \Delta is stronger, than in Bi2212. Comparison of our
theoretical data with recent bulk sensitive high-energy angle-resolved
photoemission (ARPES) data for NCCO provides good semiquantitative agreement.
Based on that comparison alternative explanation of the van-Hove singularity at
-0.3 eV is proposed. Optical conductivity both for Bi2212 and NCCO is also
calculated within LDA+DMFT+Sigma_k and compared with experimental results,
demonstrating satisfactory agreement.Comment: 8 pages, 10 figures, 1 tabl
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