13,475 research outputs found
Magnetic-field and doping dependence of low-energy spin fluctuations in the antiferroquadrupolar compound Ce(1-x)La(x)B(6)
CeB(6) is a model compound exhibiting antiferroquadrupolar (AFQ) order, its
magnetic properties being typically interpreted within localized models. More
recently, the observation of strong and sharp magnetic exciton modes forming in
its antiferromagnetic (AFM) state at both ferromagnetic and AFQ wave vectors
suggested a significant contribution of itinerant electrons to the spin
dynamics. Here we investigate the evolution of the AFQ excitation upon the
application of an external magnetic field and the substitution of Ce with
non-magnetic La, both parameters known to suppress the AFM phase. We find that
the exciton energy decreases proportionally to T_N upon doping. In field, its
intensity is suppressed, while its energy remains constant. Its disappearance
above the critical field of the AFM phase is preceded by the formation of two
modes, whose energies grow linearly with magnetic field upon entering the AFQ
phase. These findings suggest a crossover from itinerant to localized spin
dynamics between the two phases, the coupling to heavy-fermion quasiparticles
being crucial for a comprehensive description of the magnon spectrum.Comment: Extended version with a longer introduction and an additional figure.
6 pages and 5 figure
Charge states and magnetic ordering in LaMnO3/SrTiO3 superlattices
We investigated the magnetic and optical properties of
[(LaMnO3)n/(SrTiO3)8]20 (n = 1, 2, and 8) superlattices grown by pulsed laser
deposition. We found a weak ferromagnetic and semiconducting state developed in
all superlattices. An analysis of the optical conductivity showed that the
LaMnO3 layers in the superlattices were slightly doped. The amount of doping
was almost identical regardless of the LaMnO3 layer thickness up to eight unit
cells, suggesting that the effect is not limited to the interface. On the other
hand, the magnetic ordering became less stable as the LaMnO3 layer thickness
decreased, probably due to a dimensional effect.Comment: 17 pages including 4 figures, accepted for publication in Phys. Rev.
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
Hysteresis and the dynamic phase transition in thin ferromagnetic films
Hysteresis and the non-equilibrium dynamic phase transition in thin magnetic
films subject to an oscillatory external field have been studied by Monte Carlo
simulation. The model under investigation is a classical Heisenberg spin system
with a bilinear exchange anisotropy in a planar thin film geometry with
competing surface fields. The film exhibits a non-equilibrium phase transition
between dynamically ordered and dynamically disordered phases characterized by
a critical temperature Tcd, whose location of is determined by the amplitude H0
and frequency w of the applied oscillatory field. In the presence of competing
surface fields the critical temperature of the ferromagnetic-paramagnetic
transition for the film is suppressed from the bulk system value, Tc, to the
interface localization-delocalization temperature Tci. The simulations show
that in general Tcd < Tci for the model film. The profile of the time-dependent
layer magnetization across the film shows that the dynamically ordered and
dynamically disordered phases coexist within the film for T < Tcd. In the
presence of competing surface fields, the dynamically ordered phase is
localized at one surface of the film.Comment: PDF file, 21 pages including 8 figure pages; added references,typos
added; to be published in PR
Simple scheme for expanding a polarization-entangled W state by adding one photon
We propose a simple scheme for expanding a polarization-entangled W state. By
mixing a single photon and one of the photons in an n-photon W state at a
polarization-dependent beam splitter (PDBS), we can obtain an (n+1)-photon W
state after post-selection. Our scheme also opens the door for generating
n-photon W states using single photons and linear optics.Comment: 3 pages, 2 figure
Development of a test bench for drip irrigation electronic valve
Background: Efficiency of a water management and irrigation control system is important for improved production and quality of crops. Electronic valve is one of the most important components for the irrigation management system, and the performance is characterized by the flow-pressure relationships. In the study, a test bench was developed to test electronic valves for irrigation management systems.
Methods: A multistage pump (Model: DRL10-8; DOOCH, Korea), flow rate sensors (Model: E-MAG-I, AUTOFLOW, Korea), and pressure sensors (Model: A-10; WIKA, Germany) were used to construct the test bench. A control program was coded to control the pump operation. The flow rate was set at four different levels (20, 40, 60, 80 m3/h) using the multistage pump. Flow rate and pressure sensors were installed before and after the test electric valve. Data were collected through a wireless sensor network. The electric valve was controlled remotely by the software developed using C # (visual studio 2010, USA).
Results& discussion: The experimental results showed that the error ranges were 2% at 20 m3/h and 7% at 80 m3/h. We found that the flow rate within 20 ~ 80 m3/h and the pressure loss within 2 ~ 10 bar measured before and after the electric valve were linearly plotted. The pressure decreased 10% before and after the solenoid valve. The delay time need to be considered for stable flow control. To solve this problem, relief valve was installed to remove the flow rate exceeding the specified value.
Conclusion: The test bench should a favourable performance, and will be used to test and compare electronic valves
On the existence of solutions to the relativistic Euler equations in 2 spacetime dimensions with a vacuum boundary
We prove the existence of a wide class of solutions to the isentropic
relativistic Euler equations in 2 spacetime dimensions with an equation of
state of the form that have a fluid vacuum boundary. Near the fluid
vacuum boundary, the sound speed for these solutions are monotonically
decreasing, approaching zero where the density vanishes. Moreover, the fluid
acceleration is finite and bounded away from zero as the fluid vacuum boundary
is approached. The existence results of this article also generalize in a
straightforward manner to equations of state of the form
with .Comment: A major revision of the second half of the pape
Dynamical elastic bodies in Newtonian gravity
Well-posedness for the initial value problem for a self-gravitating elastic
body with free boundary in Newtonian gravity is proved. In the material frame,
the Euler-Lagrange equation becomes, assuming suitable constitutive properties
for the elastic material, a fully non-linear elliptic-hyperbolic system with
boundary conditions of Neumann type. For systems of this type, the initial data
must satisfy compatibility conditions in order to achieve regular solutions.
Given a relaxed reference configuration and a sufficiently small Newton's
constant, a neigborhood of initial data satisfying the compatibility conditions
is constructed
Effect of Spatial Charge Inhomogeneity on 1/f Noise Behavior in Graphene
Scattering mechanisms in graphene are critical to understanding the limits of
signal-to-noise-ratios of unsuspended graphene devices. Here we present the
four-probe low frequency noise (1/f) characteristics in back-gated single layer
graphene (SLG) and bilayer graphene (BLG) samples. Contrary to the expected
noise increase with the resistance, the noise for SLG decreases near the Dirac
point, possibly due to the effects of the spatial charge inhomogeneity. For
BLG, a similar noise reduction near the Dirac point is observed, but with a
different gate dependence of its noise behavior. Some possible reasons for the
different noise behavior between SLG and BLG are discussed.Comment: 28 pages, 3 figures + 3 supplement figure
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