5,711 research outputs found
Spin-torque generation by dc or ac voltages in magnetic layered structures
A general expression of the current induced spin torque in a magnetic layered
structure in the presence of external dc or ac voltages is derived in the
framework of the scattering matrix approach. A detailed analysis is performed
for a magnetic-nonmagnetic-magnetic trilayer connected to external leads in the
presence of dc voltage bias in the ballistic regime. Alternatively, the
possibility of producing spin torque by means of the adiabatic ac modulation of
external gate voltages (quantum pumping) is proposed and discussed
Transport and Magnetic Properties of FexVse2 (x = 0 - 0.33)
We present our results of the effect of Fe intercalation on the structural,
transport and magnetic properties of 1T-VSe2. Intercalation of iron, suppresses
the 110K charge density wave (CDW) transition of the 1T-VSe2. For the higher
concentration of iron, formation of a new kind of first order transition at
160K takes place, which go on stronger for the 33% Fe intercalation.
Thermopower of the FexVSe2 compounds (x = 0 - 0.33), however do not show any
anomaly around the transition. The intercalation of Fe does not trigger any
magnetism in the weak paramagnetic 1T-VSe2, and Fe is the low spin state of
Fe3+.Comment: 7 pages, 8 figures, 2 table
On the origin of \gamma-ray emission in \eta\ Carina
\eta\ Car is the only colliding-wind binary for which high-energy \gamma\
rays are detected. Although the physical conditions in the shock region change
on timescales of hours to days, the variability seen at GeV energies is weak
and on significantly longer timescales. The \gamma-ray spectrum exhibits two
features that can be interpreted as emission from the shocks on either side of
the contact discontinuity. Here we report on the first time-dependent modelling
of the non-thermal emission in \eta\ Car. We find that emission from primary
electrons is likely not responsible for the \gamma-ray emission, but
accelerated protons interacting with the dense wind material can explain the
observations. In our model, efficient acceleration is required at both shocks,
with the primary side acting as a hadron calorimeter, whilst on the companion
side acceleration is limited by the flow time out of the system, resulting in
changing acceleration conditions. The system therefore represents a unique
laboratory for the exploration of hadronic particle acceleration in
non-relativistic shocks.Comment: 5 pages, 4 figures, 1 table, accepted for publication in MNRAS
Letter
Tunable magnetization damping in transition metal ternary alloys
We show that magnetization damping in Permalloy, Ni80Fe20 (``Py''), can be
enhanced sufficiently to reduce post-switching magnetization precession to an
acceptable level by alloying with the transition metal osmium (Os). The damping
increases monotonically upon raising the Os-concentration in Py, at least up to
9% of Os. Other effects of alloying with Os are suppression of magnetization
and enhancement of in-plane anisotropy. Magnetization damping also increases
significantly upon alloying with the five other transition metals included in
this study (4d-elements: Nb, Ru, Rh; 5d-elements: Ta, Pt) but never as strongly
as with Os.Comment: 4 pages, submitted to Appl. Phys. Let
The effect of isoprenaline on induction of tumours by methyl nitrosourea in the salivary and mammary glands of female wistar rats.
Pretreatment of rats with isoprenaline sulphate (IPR) stimulated DNA synthesis in both salivary and mammary gland tissues. Salivary gland tumours induced by N-methyl-N-nitrosourea (MNU) were observed for the first time in rats, but occurred only in IPR-pretreated animals given MNU during the period of IPR-stimulated DNA synthesis. The cumulative index of MNU-induced mammary tumours and the number of tumours per tumour-bearing rat were increased by IPR-pretreament only if the animals received MNU during the period of IPR-stimulated DNA synthesis
Photo-response of the conductivity in functionalized pentacene compounds
We report the first investigation of the photo-response of the conductivity
of a new class of organic semiconductors based on functionalized pentacene.
These materials form high quality single crystals that exhibit a thermally
activated resistivity. Unlike pure pentacene, the functionalized derivatives
are readily soluble in acetone, and can be evaporated or spin-cast as thin
films for potential device applications. The electrical conductivity of the
single crystal materials is noticeably sensitive to ambient light changes. The
purpose, therefore, of the present study, is to determine the nature of the
photo-response in terms of carrier activation vs. heating effects, and also to
measure the dependence of the photo-response on photon energy. We describe a
new method, involving the temperature dependent photo-response, which allows an
unambiguous identification of the signature of heating effects in materials
with a thermally activated conductivity. We find strong evidence that the
photo-response in the materials investigated is predominantly a highly
localized heating mechanism. Wavelength dependent studies of the photo-response
reveal resonant features and cut-offs that indicate the photon energy
absorption is related to the electronic structure of the material.Comment: Preprint: 18 pages total,7 figure
Forces from highly focused laser beams: modeling, measurement and application to refractive index measurements
The optical forces in optical tweezers can be robustly modeled over a broad
range of parameters using generalsed Lorenz-Mie theory. We describe the
procedure, and show how the combination of experimental measurement of
properties of the trap coupled with computational modeling, can allow unknown
parameters of the particle - in this case, the refractive index - to be
determined.Comment: 5 pages, 4 figures, presented at 17th AIP Congress, Brisbane, 200
Thermal-magnetic noise measurement of spin-torque effects on ferromagnetic resonance in MgO-based magnetic tunnel junctions
Thermal-magnetic noise at ferromagnetic resonance (T-FMR) can be used to
measure magnetic perpendicular anisotropy of nanoscale magnetic tunnel
junctions (MTJs). For this purpose, T-FMR measurements were conducted with an
external magnetic field up to 14 kOe applied perpendicular to the film surface
of MgO-based MTJs under a dc bias. The observed frequency-field relationship
suggests that a 20 A CoFeB free layer has an effective demagnetization field
much smaller than the intrinsic bulk value of CoFeB, with 4PiMeff = (6.1 +/-
0.3) kOe. This value is consistent with the saturation field obtained from
magnetometry measurements on extended films of the same CoFeB thickness.
In-plane T-FMR on the other hand shows less consistent results for the
effective demagnetization field, presumably due to excitations of more complex
modes. These experiments suggest that the perpendicular T-FMR is preferred for
quantitative magnetic characterization of nanoscale MTJs.Comment: 10 pages, 3 figures, accepted by AP
Chiral spintronics
As spins move through a chiral electric field, the resulting spin current can acquire chirality through a spin–orbit interaction. Such spin currents are highly useful in creating spin–orbit torques that can be used to manipulate chiral topological magnetic excitations, for example, chiral magnetic domain walls or skyrmions. When the chiral domain walls form composite domain walls, via an antiferromagnetic exchange coupling, novel phenomena, including an exchange coupling torque and domain wall drag, are observed. Here, we review recent progress in the generation and functionalities of spin currents derived from or acting on chiral structures. By bringing together advances in chiral molecules, chiral magnetic structures and chiral topological matter, we provide an outlook towards potential applications
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