11,163 research outputs found
Broadband probing magnetization dynamics of the coupled vortex state permalloy layers in nanopillars
Broadband magnetization response of coupled vortex state magnetic dots in
layered nanopillars was explored as a function of in-plane magnetic field and
interlayer separation. For dipolarly coupled circular Py(25 nm)/Cu(20 nm)/Py(25
nm) nanopillars of 600 nm diameter, a small in-plane field splits the
eigenfrequencies of azimuthal spin wave modes inducing an abrupt transition
between in-phase and out-of-phase kinds of the low-lying coupled spin wave
modes. The critical field for this splitting is determined by antiparallel
chiralities of the vortices in the layers. Qualitatively similar (although more
gradual) changes occur also in the exchange coupled Py(25 nm)/Cu(1 nm)/Py(25
nm) tri-layer nanopillars. These findings are in qualitative agreement with
micromagnetic dynamic simulations
Por que consumir pescado é estratégico para o Brasil?
bitstream/item/79994/1/ADM135.pdfFormato eletrônico. Disponível também em: Dourados News, Agronline, ZooNews, AgoraMS, BBC News, Folha do MS, Infobibos
Low frequency noise due to magnetic inhomogeneities in submicron FeCoB/MgO/FeCoB magnetic tunnel junctions
We report on room temperature low frequency noise due to magnetic
inhomogeneities/domain walls (MI/DWs) in elliptic submicron FeCoB/MgO/FeCoB
magnetic tunnel junctions with an area between 0.0245 and 0.0675{\mu}m2. In the
smaller area junctions we found an unexpected random telegraph noise (RTN1),
deeply in the parallel state, possibly due to stray field induced MI/DWs in the
hard layer. The second noise source (RTN2) is observed in the antiparallel
state for the largest junctions. Strong asymmetry of RTN2 and of related
resistance steps with current indicate spin torque acting on the MI/DWs in the
soft layer at current densities below 5x10^5 A/cm2.Comment: 12 pages, 4 figure
Compact Radio Sources within 30" of Sgr A*: Proper Motions, Stellar Winds and the Accretion Rate onto Sgr A*
Recent broad-band 34 and 44 GHz radio continuum observations of the Galactic
center have revealed 41 massive stars identified with near-IR counterparts, as
well as 44 proplyd candidates within 30" of Sgr A*. Radio observations obtained
in 2011 and 2014 have been used to derive proper motions of eight young stars
near Sgr A*. The accuracy of proper motion estimates based on near-IR
observations by Lu et al. and Paumard et al. have been investigated by using
their proper motions to predict the 2014 epoch positions of near-IR stars and
comparing the predicted positions with those of radio counterparts in the 2014
radio observations. Predicted positions from Lu et al. show an rms scatter of 6
mas relative to the radio positions, while those from Paumard et al. show rms
residuals of 20 mas, which is mainly due to uncertainties in the IR-based
proper motions. Under the assumption of homogeneous ionized winds, we also
determine the mass-loss rates of 11 radio stars, finding rates that are on
average 2 times smaller than those determined from model atmosphere
calculations and near-IR data. Clumpiness of ionized winds would reduce the
mass loss rate of WR and O stars by additional factors of 3 and 10,
respectively. One important implication of this is a reduction in the expected
mass accretion rate onto Sgr A* from stellar winds by nearly an order of
magnitude to a value of few \msol\ yr. Finally, we
present the positions of 318 compact 34.5 GHz radio sources within 30\arcs\ of
Sgr A*. At least 45 of these have stellar counterparts in the near-IR
(2.18 m) and (3.8m) bands.Comment: 30 pages, 4 figures, ApJ (in press
Ca impurity in small mixed He-He clusters
The structure of small mixed helium clusters doped with one calcium atom has
been determined within the diffusion Monte Carlo framework. The results show
that the calcium atom sits at the He-He interface. This is in agreement
with previous studies, both experimental and theoretical, performed for large
clusters. A comparison between the results obtained for the largest cluster we
have considered for each isotope shows a clear tendency of the Ca atom to
reside in a deep dimple at the surface of the cluster for He clusters, and
to become fully solvated for He clusters. We have calculated the absorption
spectrum of Ca around the transition and have found that
it is blue-shifted from that of the free-atom transition by an amount that
depends on the size and composition of the cluster.Comment: 24 pages, 11 figures. Accepted on Journal of Chemical Physic
- …