Search results for " Bias"
showing 10 items of 437 documents
Adiabatic quantum pumping, magnification effects and quantum size effects of spin-torque in magnetic tunnel junctions
2010
We study the adiabatic quantum pumping and quantum size effects of spin-torque in a magnetic tunnel junction within a scattering matrix approach. Quantum size effects are predicted in the presence of a dc bias as a function of the thickness of the normal metal layer inserted between two magnetic layers and of the fixed magnetic layer. In the presence of ac voltages, the results for the spin-torque show a peculiar magnification effect and advantages of spin-torque pumping in actual devices are also discussed.
Neutron Scattering in Nanomagnetism
2015
Abstract Polarized neutron reflectometry (PNR) has played an essential role for the exploration of nanomagnetic and spintronic materials, including exchange coupled magnetic superlattices, exchange bias systems between ferromagnetic and antiferromagnetic films, spin valves, exchange springs between soft and hard magnetic films, superconducting proximity effects, periodic lateral magnetic patterns, and magnetic nanoparticles. The main virtues of PNR are depth-resolved vector magnetometry in the film plane, high sensitivity to magnetic interfaces, and statistical analysis of magnetic domain fluctuations. Recently the capabilities of PNR have been carried over from steady state to dynamic inve…
Pumping of single electrons with a traveling wave
1995
Abstract We describe the operation and performance of a one-dimensional chain of small metallic islands whose potentials are modulated in a wave-like manner. The sinusoidal voltages, applied to the gate electrodes, carry individual charges coherently through the array. In practice, the wave-like potential is induced on the gates by a surface acoustic wave (SAW) traveling on a piezoelectric substrate. The resulting transfer of charges should produce a DC current I = ± ef through the chain, where f is the frequency of the wave and the sign ofthe current depends on the value of the common DC bias of the islands as well as on the direction of the wave propagation. We observe, however, a much sm…
Microwave induced co-tunneling in single electron tunneling transistors
2002
Abstract The influence of microwaves on the co-tunneling in single electron tunneling transistors has been investigated as function of frequency and power in the temperature range from 150 to 500 mK. All 20 low frequency connections and the RF line were filtered, and the whole cryostat was suspended on rubber bellows. Cross-talk was minimized by using individual coaxial lines between the sample and the room temperature electronics. The co-tunneling experiments were performed at zero DC bias current by measuring the voltage response to a very small amplitude 2 Hz current modulation with the gate voltage fixed at maximum Coulomb blockade. With the microwave signal applied to one side of the t…
Magnetization dynamics in microscopic spin-valve elements: Shortcomings of the macrospin picture
2007
We have studied ultrafast magnetodynamics in micropatterned spin-valve structures using time-resolved x-ray photoemission electron microscopy combined with x-ray magnetic circular dichroism. Exciting the system with ultrafast field pulses of $250\phantom{\rule{0.3em}{0ex}}\mathrm{ps}$ width, we find the dynamic response of the free layer to fall into two distinctly different contributions. On the one hand, it exhibits localized spin wave modes that strongly depend on the shape of the micropattern. A field pulse applied perpendicular to the exchange bias field along the diagonal of a square pattern leads to the excitation of a standing spin wave mode with two nodes along the field direction.…
Comment on "Dynamics and properties of waves in a modified Noguchi electrical transmission line"
2016
A recent paper [Phys. Rev. E 91, 022925 (2015)PRESCM1539-375510.1103/PhysRevE.91.022925] presents the derivation of the nonlinear equation modeling envelope waves in a specific case of band passed filter discrete nonlinear electrical transmission line (NLTL), called "A modified Noguchi electrical transmission line" according to the authors. Using the reductive perturbation approach in the semidiscrete approximation, they showed that the modulated waves propagating in this NLTL are described by the ordinary nonlinear Schrodinger (NLS) equation. On the basis of their results, the authors claimed that all previous works on the band passed filter NLTL, which considered the vanishing of the dc c…
Charged-particle multiplicities in pp interactions at s=900 GeV measured with the ATLAS detector at the LHC
2010
The first measurements from proton-proton collisions recorded with the ATLAS detector at the LHC are presented. Data were collected in December 2009 using a minimum-bias trigger during collisions at a centre-of-mass energy of 900 GeV. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity, and the relationship between mean transverse momentum and charged-particle multiplicity are measured for events with at least one charged particle in the kinematic range vertical bar eta vertical bar 500 MeV. The measurements are compared to Monte Carlo models of proton-proton collisions and to results from other experiments at the same centre-of-mass energy. The charg…
Impact of Energy and Luminosity upgrades at LHC on the Physics program of ATLAS
2002
The impact on the physics capabilities of the ATLAS detector of possible LHC upgrades is discussed. As a benchmark, an increase in the luminosity by a factor of ten is considered. For comparison, a doubling of the LHC energy is also explored. Both upgrades significantly enhance the physics capabilities of ATLAS. As measured in terms of the mass reach for new particles, the energy upgrade is more powerful. However, in cases where the effect of an upgrade is to increase the precision of measurements as a result of the larger data samples, the luminosity upgrade can be at least as powerful. The pile-up of minimum bias events at higher luminosity could limit the physics performance of ATLAS in …
Constraining nPDFs with inclusive pions and direct photons at forward rapidities in p+Pb collisions at the LHC
2014
Abstract In this talk, we present NLO pQCD predictions for inclusive pion and direct photon nuclear modifications in p + Pb collisions at mid- and forward rapidities at the LHC. In addition to the minimum bias predictions, we also address the centrality dependence with spatially dependent nuclear PDFs. To understand which regions of the nuclear momentum fraction x 2 these observables predominantly probe, we present also the underlying x 2 distributions at different rapidities. We are led to conclude that the isolated photons at forward rapidities are more sensitive to the small- x 2 dynamics than the inclusive pions.
Point-to-point readout for the ALICE EMCal detector
2014
Abstract It is anticipated that the LHC will deliver Pb+Pb collisions at a minimum bias interaction rate of about 50 kHz after the second long shutdown of the LHC in 2018. This will be roughly two orders of magnitude greater than the current data recording rate capability of the ALICE experiment. Therefore a major upgrade of the ALICE detector is planned for the next shutdown to enable ALICE to record data at the full Pb+Pb minimum bias interaction rate delivered by the LHC. A new point-to-point readout system for the electromagnetic calorimeter (EMCal) of ALICE has been developed, to replace the legacy readout bus, that essentially accomplishes this goal, and is being installed during the …