5,318 research outputs found
Current-driven resonant excitation of magnetic vortex
A magnetic vortex core in a ferromagnetic circular nanodot has a resonance
frequency originating from the confinement of the vortex core. By the
micromagnetic simulation including the spin-transfer torque, we show that the
vortex core can be resonantly excited by an AC (spin-polarized) current through
the dot and that the resonance frequency can be tuned by the dot shape. The
resistance measurement under the AC current successfully detects the resonance
at the frequency consistent with the simulation.Comment: 16 pages, 4 figure
Current-driven domain wall motion in magnetic wires with asymmetric notches
Current-driven domain wall (DW) motion in magnetic wires with asymmetric
notches was investigated by means of magnetic force microscopy. It was found
that the critical current density necessary for the current-driven DW motion
depended on the propagation direction of the DW. The DW moved more easily in
the direction along which the slope of the asymmetric notch was less inclined.Comment: 11 pages, 2 figure
Magnetization Losses in Multifilament Coated Superconductors
We report the results of a study of the magnetization losses in experimental
multifilament, as well as control (uniform), coated superconductors exposed to
time-varying magnetic field of various frequencies. Both the hysteresis loss,
proportional to the sweep rate of the applied magnetic field, and the coupling
loss, proportional to the square of the sweep rate, have been observed. A
scaling is found that allows us to quantify each of these contributions and
extrapolate the results of the experiment beyond the envelope of accessible
field amplitude and frequency. The combined loss in the multifilament conductor
is reduced by about 90% in comparison with the uniform conductor at full field
penetration at sweep rate as high as 3T/s
Age of the Universe: Influence of the Inhomogeneities on the global Expansion-Factor
For the first time we calculate quantitatively the influence of
inhomogeneities on the global expansion factor by averaging the Friedmann
equation. In the framework of the relativistic second-order
Zel'dovich-approximation scheme for irrotational dust we use observational
results in form of the normalisation constant fixed by the COBE results and we
check different power spectra, namely for adiabatic CDM, isocurvature CDM, HDM,
WDM, Strings and Textures. We find that the influence of the inhomogeneities on
the global expansion factor is very small. So the error in determining the age
of the universe using the Hubble constant in the usual way is negligible. This
does not imply that the effect is negligible for local astronomical
measurements of the Hubble constant. Locally the determination of the
redshift-distance relation can be strongly influenced by the peculiar velocity
fields due to inhomogeneities. Our calculation does not consider such effects,
but is contrained to comparing globally homogeneous and averaged inhomogeneous
matter distributions. In addition we relate our work to previous treatments.Comment: 10 pages, version accepted by Phys. Rev.
Propagation of a magnetic domain wall in magnetic wires with asymmetric notches
The propagation of a magnetic domain wall (DW) in a submicron magnetic wire
consisting of a magnetic/nonmagnetic/magnetic trilayered structure with
asymmetric notches was investigated by utilizing the giant magnetoresistance
effect. The propagation direction of a DW was controlled by a pulsed local
magnetic field, which nucleates the DW at one of the two ends of the wire. It
was found that the depinning field of the DW from the notch depends on the
propagation direction of the DW.Comment: 12 pages, 3 figure
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
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