1,060 research outputs found
Domain wall displacement by remote spin-current injection
We demonstrate numerically the ability to displace a magnetic domain wall by
a remote spin current injection. We consider a long and narrow magnetic
nanostripe with a single domain wall (DW). The spin-polarized current is
injected perpendicularly to the plane of the film (CPP) through a small
nanocontact which is located at certain distance from the domain wall initial
position. We show theoretically that the DW motion can be initiated not only by
conventional spin-transfer torque but also by indirect spin-torque, created by
a remote spin-current injection and then transferred to the DW by the
exchange-spring mechanism. An analytical description of this effect is
proposed. This finding may lead to a solution of bottleneck problems of DW
motion-based spintronic and neuromorphic devices with perpendicular
spin-current injection.Comment: 6 pages, 4 figure
Coupling efficiency for phase locking of a spin transfer oscillator to a microwave current
The phase locking behavior of spin transfer nano-oscillators (STNOs) to an
external microwave signal is experimentally studied as a function of the STNO
intrinsic parameters. We extract the coupling strength from our data using the
derived phase dynamics of a forced STNO. The predicted trends on the coupling
strength for phase locking as a function of intrinsic features of the
oscillators i.e. power, linewidth, agility in current, are central to optimize
the emitted power in arrays of mutually coupled STNOs
A 6-year global cloud climatology from the Atmospheric InfraRed Sounder AIRS and a statistical analysis in synergy with CALIPSO and CloudSat
We present a six-year global climatology of cloud properties, obtained from observations of the Atmospheric Infrared Sounder (AIRS) onboard the NASA Aqua satellite. Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) combined with CloudSat observations, both missions launched as part of the A-Train in 2006, provide a unique opportunity to evaluate the retrieved AIRS cloud properties such as cloud amount and height. In addition, they permit to explore the vertical structure of different cloud types. AIRS-LMD cloud detection agrees with CALIPSO about 85% over ocean and about 75% over land. Global cloud amount has been estimated from 66% to 74%, depending on the weighting of not cloudy AIRS footprints by partial cloud cover from 0 to 0.3. 42% of all clouds are high clouds, and about 42% of all clouds are single layer low-level clouds. The "radiative" cloud height determined by the AIRS-LMD retrieval corresponds well to the height of the maximum backscatter signal and of the "apparent middle" of the cloud. Whereas the real cloud thickness of high opaque clouds often fills the whole troposphere, their "apparent" cloud thickness (at which optical depth reaches about 5) is on average only 2.5 km. The real geometrical thickness of optically thin cirrus as identified by AIRS-LMD is identical to the "apparent" cloud thickness with an average of about 2.5 km in the tropics and midlatitudes. High clouds in the tropics have slightly more diffusive cloud tops than at higher latitudes. In general, the depth of the maximum backscatter signal increases nearly linearly with increasing "apparent" cloud thickness. For the same "apparent" cloud thickness optically thin cirrus show a maximum backscatter about 10% deeper inside the cloud than optically thicker clouds. We also show that only the geometrically thickest opaque clouds and (the probably surrounding anvil) cirrus penetrate the stratosphere in the tropics
Spin injection in a single metallic nanoparticle: a step towards nanospintronics
We have fabricated nanometer sized magnetic tunnel junctions using a new
nanoindentation technique in order to study the transport properties of a
single metallic nanoparticle. Coulomb blockade effects show clear evidence for
single electron tunneling through a single 2.5 nm Au cluster. The observed
magnetoresistance is the signature of spin conservation during the transport
process through a non magnetic cluster.Comment: 3 page
Parallel pumping of magnetic vortex gyrations in spin-torque nano-oscillators
We experimentally demonstrate that large magnetic vortex oscillations can be
parametrically excited in a magnetic tunnel junction by the injection of
radio-frequency (rf) currents at twice the natural frequency of the gyrotropic
vortex core motion. The mechanism of excitation is based on the parallel
pumping of vortex motion by the rf orthoradial field generated by the injected
current. Theoretical analysis shows that experimental results can be
interpreted as the manifestation of parametric amplification when rf current is
small, and of parametric instability when rf current is above a certain
threshold. By taking into account the energy nonlinearities, we succeed to
describe the amplitude saturation of vortex oscillations as well as the
coexistence of stable regimes.Comment: Submitted to Phys. Rev. Let
Dynamics of two coupled vortices in a spin valve nanopillar excited by spin transfer torque
We investigate the dynamics of two coupled vortices driven by spin transfer.
We are able to independently control with current and perpendicular field, and
to detect, the respective chiralities and polarities of the two vortices. For
current densities above , a highly coherent signal
(linewidth down to 46 kHz) can be observed, with a strong dependence on the
relative polarities of the vortices. It demonstrates the interest of using
coupled dynamics in order to increase the coherence of the microwave signal.
Emissions exhibit a linear frequency evolution with perpendicular field, with
coherence conserved even at zero magnetic field
The digital data processing concepts of the LOFT mission
The Large Observatory for X-ray Timing (LOFT) is one of the five mission
candidates that were considered by ESA for an M3 mission (with a launch
opportunity in 2022 - 2024). LOFT features two instruments: the Large Area
Detector (LAD) and the Wide Field Monitor (WFM). The LAD is a 10 m 2 -class
instrument with approximately 15 times the collecting area of the largest
timing mission so far (RXTE) for the first time combined with CCD-class
spectral resolution. The WFM will continuously monitor the sky and recognise
changes in source states, detect transient and bursting phenomena and will
allow the mission to respond to this. Observing the brightest X-ray sources
with the effective area of the LAD leads to enormous data rates that need to be
processed on several levels, filtered and compressed in real-time already on
board. The WFM data processing on the other hand puts rather low constraints on
the data rate but requires algorithms to find the photon interaction location
on the detector and then to deconvolve the detector image in order to obtain
the sky coordinates of observed transient sources. In the following, we want to
give an overview of the data handling concepts that were developed during the
study phase.Comment: Proc. SPIE 9144, Space Telescopes and Instrumentation 2014:
Ultraviolet to Gamma Ray, 91446
Inverse Spin Hall Effect in nanometer-thick YIG/Pt system
High quality nanometer-thick (20 nm, 7 nm and 4 nm) epitaxial YIG films have
been grown on GGG substrates using pulsed laser deposition. The Gilbert damping
coefficient for the 20 nm thick films is 2.3 x 10-4 which is the lowest value
reported for sub-micrometric thick films. We demonstrate Inverse spin Hall
effect (ISHE) detection of propagating spin waves using Pt. The amplitude and
the lineshape of the ISHE voltage correlate well to the increase of the Gilbert
damping when decreasing thickness of YIG. Spin Hall effect based
loss-compensation experiments have been conducted but no change in the
magnetization dynamics could be detected
- …