1,005 research outputs found
Photoemission Spectral Weight Transfer and Mass Renormalization in the Fermi-Liquid System LaSrTiO
We have performed a photoemission study of LaSrTiO near
the filling-control metal-insulator transition (MIT) as a function of hole
doping. Mass renormalization deduced from the spectral weight and the width of
the quasi-particle band around the chemical potential is compared with
that deduced from the electronic specific heat. The result implies that, near
the MIT, band narrowing occurs strongly in the vicinity of . Spectral
weight transfer occurs from the coherent to the incoherent parts upon
antiferromagnetic ordering, which we associate with the partial gap opening at
.Comment: 4 pages, 3 figure
Simple bonding technique for high-temperature ceramic coatings
Coatings, consisting of zirconia powder bonded with orthophosphoric acid and a small amount of hydrofluoric acid, are hard, strong, and refractory, resist thermal shock, and provide good thermal protection. After the aqueous coating is applied to a metallic surface, only a 600 deg F cure is required before service
Investigation of the use of microwave image line integrated circuits for use in radiometers and other microwave devices in X-band and above
Program results are described in which the use of a/high permittivity rectangular dielectric image waveguide has been investigated for use in microwave and millimeter wavelength circuits. Launchers from rectangular metal waveguide to image waveguide are described. Theoretical and experimental evaluations of the radiation from curved image waveguides are given. Measurements of attenuation due to conductor and dielectric losses, adhesives, and gaps between the dielectric waveguide and the image plane are included. Various passive components are described and evaluations given. Investigations of various techniques for fabrication of image waveguide circuits using ceramic waveguides are also presented. Program results support the evaluation of the image line approach as an advantageous method for realizing low loss integrated electronic circuits for X-band and above
The electrokinetic behavior of calcium oxalate monohydrate in macromolecular solutions
Electrophoretic mobilities were measured for calcium oxalate monohydrate (COM) in solutions containing macromolecules. Two mucopolysaccharides (sodium heparin and chrondroitin sulfate) and two proteins (positively charged lysozyme and negatively charged bovine serum albumin) were studied as adsorbates. The effects of pH, calcium oxalate surface charge (varied by calcium or oxalate ion activity), and citrate concentration were investigated. All four macromolecules showed evidence for chemical adsorption. The macromolecule concentrations needed for reversing the surface charge indicated that the mucopopolysacchrides have greater affinity for the COM surface than the proteins. The amount of proteins that can chemically adsorb appears to be limited to approximately one monomolecular layer. When the surface charge is high, an insufficient number of proteins can chemically adsorb to neutralize or reverse the surface charge. The remaining surface charge is balanced by proteins held near the surface by longer range electrostatic forces only. Citrate ions at high concentrations appear to compete effectively with the negative protein for surface sites but show no evidence for competing with the positively charged protein
Universal Scaling Behavior of Anomalous Hall Effect and Anomalous Nernst Effect in Itinerant Ferromagnets
Anomalous Hall effect (AHE) and anomalous Nernst effect (ANE) in a variety of
ferromagnetic metals including pure metals, oxides, and chalcogenides, are
studied to obtain unified understandings of their origins. We show a universal
scaling behavior of anomalous Hall conductivity as a function of
longitudinal conductivity over five orders of magnitude, which is
well explained by a recent theory of the AHE taking into account both the
intrinsic and extrinsic contributions. ANE is closely related with AHE and
provides us with further information about the low-temperature electronic state
of itinerant ferromagnets. Temperature dependence of transverse Peltier
coefficient shows an almost similar behavior among various
ferromagnets, and this behavior is in good agreement quantitatively with that
expected from the Mott rule.Comment: 4pages, 4figures, 1tabl
Studies of the Anomalous Hall Effect and Magnetic Structure of Nd2Mo2O7 -Test of the Chirality Mechanism-
Neutron scattering studies have been carried out under the magnetic fields
H//[0_11] and H//[001] on a single crystal of Nd2Mo2O7, whose Hall
resistivity(rhoH) exhibits quite unusual H- and temperature(T)-dependences.
Material parameters such as the single ion anisotropies of the Mo- and Nd-
moments and exchange coupling constants among the Mo-Mo, Mo-Nd and Nd-Nd
moments, have been determined to reproduce various kinds of experimental data
taken as a function of H and T. For example, the neutron Bragg intensities,
magnetization curves and the magnetic specific heats have been reproduced by
the common parameters. By using the magnetic structure reproduced by these
parameters, the spin chirality (chi) of Mo spins or the fictitious magnetic
flux Phi proportional to chi has been calculated as a function of H and T by
using equation chi=, where the bracket means the statistical
average. (Note that we do not use the equation chi=x, because the
local nature of the chirality should be correctly considered.) Comparing the
calculated results with the observed rhoH, we can conclude that the unusual
behavior of rH cannot be understood consistently only by the chirality
mechanism.Comment: 16 pages, 12 fiures, submitted to J. Phys. Soc. Jp
Magneto-optics induced by the spin chirality in itinerant ferromagnet NdMoO
It is demonstrated both theoretically and experimentally that the spin
chirality associated with a noncoplanar spin configuration produces a
magneto-optical effect. Numerical study of the two-band Hubbard model on a
triangle cluster shows that the optical Hall conductivity
is proportional to the spin chirality. The detailed comparative experiments on
pyrochlore-type molybdates MoO with Nd (Ising-like moments)
and Gd (Heisenberg-like ones) clearly distinguishes the two mechanisms,
i.e., spin chirality and spin-orbit interactions. It is concluded that for
=Nd, is dominated by the spin chirality for the dc
() and the incoherent intraband optical transitions between
Mo atoms.Comment: 4 pages, 5 figures. submitted to Phys. Rev.
Temperature dependent magnetotransport around = 1/2 in ZnO heterostructures
The sequence of prominent fractional quantum Hall states up to =5/11
around =1/2 in a high mobility two-dimensional electron system confined at
oxide heterointerface (ZnO) is analyzed in terms of the composite fermion
model. The temperature dependence of \Rxx oscillations around =1/2
yields an estimation of the composite fermion effective mass, which increases
linearly with the magnetic field. This mass is of similar value to an enhanced
electron effective mass, which in itself arises from strong electron
interaction. The energy gaps of fractional states and the temperature
dependence of \Rxx at =1/2 point to large residual interactions between
composite fermions.Comment: 5 pages, 4 Figure
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