498,903 research outputs found
Electromagnons and instabilities in magnetoelectric materials with non-collinear spin orders
We show that strong electromagnon peaks can be found in absorption spectra of
non-collinear magnets exhibiting a linear magnetoelectric effect. The
frequencies of these peaks coincide with the frequencies of antiferromagnetic
resonances and the ratio of the spectral weights of the electromagnon and
antiferromagnetic resonance is related to the ratio of the static
magnetoelectric constant and magnetic susceptibility. Using a Kagome lattice
antiferromagnet as an example, we show that frustration of spin ordering gives
rise to magnetoelastic instabilities at strong spin-lattice coupling, which
transform a non-collinear magnetoelectric spin state into a collinear
multiferroic state with a spontaneous electric polarization and magnetization.
The Kagome lattice antiferromagnet also shows a ferroelectric
incommensurate-spiral phase, where polarization is induced by the exchange
striction mechanism.Comment: 9 pages, 4 figure
On-chip detection of ferromagnetic resonance of a single submicron permalloy strip
We measured ferromagnetic resonance of a single submicron ferromagnetic
strip, embedded in an on-chip microwave transmission line device. The method
used is based on detection of the oscillating magnetic flux due to the
magnetization dynamics, with an inductive pick-up loop. The dependence of the
resonance frequency on applied static magnetic field agrees very well with the
Kittel formula, demonstrating that the uniform magnetization precession mode is
being driven
Multiple scattering of classical waves: from microscopy to mesoscopy and diffusion
A tutorial discussion of the propagation of waves in random media is
presented. In first approximation the transport of the multiple scattered waves
is given by diffusion theory, but important corrections are present. These
corrections are calculated with the radiative transfer or Schwarzschild-Milne
equation, which describes intensity transport at the ``mesoscopic'' level and
is derived from the ``microscopic'' wave equation. A precise treatment of the
diffuse intensity is derived which automatically includes the effects of
boundary layers. Effects such as the enhanced backscatter cone and imaging of
objects in opaque media are also discussed within this framework. In the second
part the approach is extended to mesoscopic correlations between multiple
scattered intensities which arise when scattering is strong. These correlations
arise from the underlying wave character. The derivation of correlation
functions and intensity distribution functions is given and experimental data
are discussed. Although the focus is on light scattering, the theory is also
applicable to micro waves, sound waves and non-interacting electrons.Comment: Review. 86 pages Latex, 32 eps-figures included. To appear in Rev.
Mod. Phy
The anapole form factor of the nucleon
The anapole form factor of the nucleon is calculated in chiral perturbation
theory in leading order. To this order, the form factor originates from the
pion cloud, and is proportional to the non-derivative parity-violating
pion-nucleon coupling. The momentum dependence of the form factor - and in
particular, its radius - is completely determined by the pion mass.Comment: 9 pages, 2 eps figures included by epsf.sty, minor changes in note
adde
Photo-ionization modelling of planetary nebulae -- II. Galactic bulge nebulae, a comparison with literature results
We have constructed photo-ionization models of five galactic bulge planetary
nebulae using our automatic method which enables a fully self-consistent
determination of the physical parameters of a planetary nebula. The models are
constrained using the spectrum, the IRAS and radio fluxes and the angular
diameter of the nebula. We also conducted a literature search for physical
parameters determined with classical methods for these nebulae. Comparison of
the distance independent physical parameters with published data shows that the
stellar temperatures generally are in good agreement and can be considered
reliable. The literature data for the electron temperature, electron density
and also for the abundances show a large spread, indicating that the use of
line diagnostics is not reliable and that the accuracy of these methods needs
to be improved. Comparison of the various abundance determinations indicates
that the uncertainty in the electron temperature is the main source of
uncertainty in the abundance determination. The stellar magnitudes predicted by
the photo-ionization models are in good agreement with observed values.Comment: Accepted for publication in MNRA
Prospective five-year subsidence analysis of a cementless fully hydroxyapatite-coated femoral hip arthroplasty component
Early subsidence >1.5 mm is considered to be a predictive factor for later aseptic loosening of the femoral component following total hip arthroplasty (THA). The aim of this study was to assess five-year subsidence rates of the cementless hydroxyapatite-coated twinSys stem (Mathys Ltd., Bettlach, Switzerland).This prospective single-surgeon series examined consecutive patients receiving a twinSys stem at Maria Middelares Hospital, Belgium. Patients aged >85 years or unable to come to follow-up were excluded. Subsidence was assessed using Ein Bild Roentgen Analyse--Femoral Component Analysis (EBRA-FCA). Additional clinical and radiographic assessments were performed. Follow-ups were prospectively scheduled at two, five, 12, 24, and 60 months.In total, 218 THA (211 patients) were included. At five years, mean subsidence was 0.66 mm (95% CI: 0.43-0.90). Of the 211 patients, 95.2% had an excellent or good Harris Hip Score. There were few radiological changes. Kaplan-Meier analysis indicated five-year stem survival to be 98.4% (95% CI: 97.6-100%).Subsidence levels of the twinSys femoral stem throughout the five years of follow-up were substantially lower than the 1.5 mm level predictive of aseptic loosening. This was reflected in the high five-year survival rate
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