203,265 research outputs found
Magnetic characterization and switching of Co nano-rings in current-perpendicular-to-plane configuration
We fabricated Co nano-rings incorporated in the vertical pseudo-spin-valve
nanopillar structures with deep submicron lateral sizes. It is shown that the
current-perpendicular-to-plane giant magnetoresistance can be used to
characterize a very small magnetic nano-ring effectively. Both the onion state
and the flux-closure vortex state are observed. The Co nano-rings can be
switched between the onion states as well as between onion and vortex states
not only by the external field but also by the perpendicularly injected dc
current
Doping and temperature-dependent optical properties of oxygen-reduced BaTiO3-d
We report on optical properties of reduced BaTiO3-d at different doping
levels including insulating and metallic samples. In all the samples, including
metallic one, we observe structural phase transitions from the changes in the
infrared-active phonon modes. Metallic ground state is confirmed by the
Drude-type lowfrequency optical reflectance. Similar to SrTiO3-d we find that
the midinfrared-absorption band in BaTiO3-d appears and grows with an increase
in the oxygen-vacancy concentration. Upon decrease in temperature from 300 K,
the midinfrared band shifts slightly to higher frequency and evolves into two
bands: the existing band and a new and smaller band at lower frequency. The
appearance of the new and smaller band seems to be correlated with the
structural phase transitionsComment: 8 pages, 7 figure
Light-Cone Distribution Amplitudes of Light Tensor Mesons in QCD
We present a study for two-quark light-cone distribution amplitudes for the
light tensor meson states with quantum number . Because
of the G-parity, the chiral-even two-quark light-cone distribution amplitudes
of this tensor meson are antisymmetric under the interchange of momentum
fractions of the quark and antiquark in the SU(3) limit, while the chiral-odd
ones are symmetric. The asymptotic leading-twist LCDAs with the strange quark
mass correction are shown. We estimate the relevant parameters, the decay
constants and , and first Gegenbauer moment , by
using the QCD sum rule method. These parameters play a central role in the
investigation of meson decaying into the tensor mesons.Comment: 18 pages, 3 Figure
Enhanced electroweak penguin amplitude in B-->VV decays
We discuss a novel electromagnetic penguin contribution to the transverse
helicity amplitudes in B decays to two vector mesons, which is enhanced by two
powers of mB/Lambda relative to the standard penguin amplitudes. This leads to
unique polarization signatures in penguin-dominated decay modes such as B-->rho
K* similar to polarization effects in the radiative decay B-->K*gamma, and
offers new opportunities to probe the magnitude and chirality of
flavour-changing neutral current couplings to photons.Comment: 4 pages, 1 figur
Light-Cone Distribution Amplitudes of Light Tensor Mesons in QCD
We present a study for two-quark light-cone distribution amplitudes for the
light tensor meson states with quantum number . Because
of the G-parity, the chiral-even two-quark light-cone distribution amplitudes
of this tensor meson are antisymmetric under the interchange of momentum
fractions of the quark and antiquark in the SU(3) limit, while the chiral-odd
ones are symmetric. The asymptotic leading-twist LCDAs with the strange quark
mass correction are shown. We estimate the relevant parameters, the decay
constants and , and first Gegenbauer moment , by
using the QCD sum rule method. These parameters play a central role in the
investigation of meson decaying into the tensor mesons.Comment: 18 pages, 3 Figure
Viscous effects on transonic airfoil stability and response
Viscous effects on transonic airfoil stability and response are investigated using an integral boundary layer model coupled to the inviscid XTRAN2L transonic small disturbance code. Unsteady transonic airloads required for stability analyses are computed using a pulse transfer function analysis including viscous effects. The pulse analysis provides unsteady aerodynamic forces for a wide range of reduced frequency in a single flow field computation. Nonlinear time marching aeroelastic solutions are presented which show the effects of viscosity on airfoil response behavior and flutter. Effects of amplitude on time marching responses are demonstrated. A state space aeroelastic model employing Pade approximants to describe the unsteady airloads is used to study the effects of viscosity on transonic airfoil stability. State space dynamic pressure root loci are in good overall agreement with time marching damping and frequency estimates. Parallel sets of results with and without viscous effects reveal the effects of viscosity on transonic unsteady airloads and aeroelastic characteristics of airfoils
Epitaxial Ferromagnetic Nanoislands of Cubic GdN in Hexagonal GaN
Periodic structures of GdN particles encapsulated in a single crystalline GaN
matrix were prepared by plasma assisted molecular beam epitaxy. High resolution
X-ray diffractometery shows that GdN islands, with rock salt structure are
epitaxially oriented to the wurtzite GaN matrix. Scanning transmission electron
microscopy combined with in-situ reflection high energy electron diffraction
allows for the study of island formation dynamics, which occurs after 1.2
monolayers of GdN coverage. Magnetometry reveals two ferromagnetic phases, one
due to GdN particles with Curie temperature of 70K and a second, anomalous room
temperature phase.Comment: 4 pages, 3 figure
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