757 research outputs found
Sensitivity of spin-torque diodes for frequency-tunable resonant microwave detection
We calculate the efficiency with which magnetic tunnel junctions can be used
as resonant detectors of incident microwave radiation via the spin-torque diode
effect. The expression we derive is in good agreement with the sensitivities we
measure for MgO-based magnetic tunnel junctions with an extended (unpatterned)
magnetic pinned layer. However, the measured sensitivities are reduced below
our estimate for a second set of devices in which the pinned layer is a
patterned synthetic antiferromagnet (SAF). We suggest that this reduction may
be due to an undesirable coupling between the magnetic free layer and one of
the magnetic layers within the etched SAF. Our calculations suggest that
optimized tunnel junctions should achieve sensitivities for resonant detection
exceeding 10,000 mV/mW.Comment: 17 pages, 2 figure
Charge pumping in magnetic tunnel junctions: Scattering theory
We study theoretically the charge transport pumped by magnetization dynamics
through epitaxial FIF and FNIF magnetic tunnel junctions (F: Ferromagnet, I:
Insulator, N: Normal metal). We predict a small but measurable DC pumping
voltage under ferromagnetic resonance conditions for collinear magnetization
configurations, which may change sign as function of barrier parameters. A much
larger AC pumping voltage is expected when the magnetizations are at right
angles. Quantum size effects are predicted for an FNIF structure as a function
of the normal layer thickness.Comment: 4 pages, 3 figures. to be published on Physical Review B Rapid
Communicatio
New Insights Into the Regulation of Natural-Killer Group 2 Member D (NKG2D) and NKG2D-Ligands: Endoplasmic Reticulum Stress and CEA-Related Cell Adhesion Molecule 1
Natural-killer group 2 member D (NKG2D) is a well-characterized activating receptor expressed by natural killer (NK) cells, NKT cells, activated CD8+ T cells, subsets of γδ+ T cells, and innate-like T cells. NKG2D recognizes multiple ligands (NKG2D-ligands) to mount an innate immune response against stressed, transformed or infected cells. NKG2D-ligand surface expression is tightly restricted on healthy cells through transcriptional and post-transcriptional mechanisms, while transformed or infected cells express the ligands as a danger signal. Recent studies have revealed that unfolded protein response (UPR) pathways during endoplasmic reticulum (ER) stress result in up-regulation of ULBP-related protein via the PERK-ATF4-CHOP pathway, which can be linked to the pathogenesis of autoimmune diseases. Transformed cells however possess mechanisms to escape NKG2D-mediated immune surveillance, such as upregulation of carcinoembryonic antigen (CEA)-related cell adhesion molecule 1 (CEACAM1), a negative regulator of NKG2D-ligands. In this review, we discuss mechanisms of NKG2D-ligand regulation, with a focus on newly discovered mechanisms that promote NKG2D-ligand expression on epithelial cells, including ER stress, and mechanisms that suppress NKG2D-ligand mediated killing of cancer cells, namely by co-expression of CEACAM1.Wellcome Trust Senior Investigator Award 106260/Z/14/Z, the European Research Council HORIZON2020/ERC grant no. 648889 (A.K.
Magnetization reversal driven by spin-injection : a mesoscopic spin-transfer effect
A mesoscopic description of spin-transfer effect is proposed, based on the
spin-injection mechanism occurring at the junction with a ferromagnet. The
effect of spin-injection is to modify locally, in the ferromagnetic
configuration space, the density of magnetic moments. The corresponding
gradient leads to a current-dependent diffusion process of the magnetization.
In order to describe this effect, the dynamics of the magnetization of a
ferromagnetic single domain is reconsidered in the framework of the
thermokinetic theory of mesoscopic systems. Assuming an Onsager
cross-coefficient that couples the currents, it is shown that spin-dependent
electric transport leads to a correction of the Landau-Lifshitz-Gilbert
equation of the ferromagnetic order parameter with supplementary diffusion
terms. The consequence of spin-injection in terms of activation process of the
ferromagnet is deduced, and the expressions of the effective energy barrier and
of the critical current are derived. Magnetic fluctuations are calculated: the
correction to the fluctuations is similar to that predicted for the activation.
These predictions are consistent with the measurements of spin-transfer
obtained in the activation regime and for ferromagnetic resonance under
spin-injection.Comment: 20 pages, 2 figure
Distribution of the magnetization reversal duration in sub-ns spin-transfer switching
We study the distribution of switching times in spin-transfer switching
induced by sub-ns current pulses in pillar-shaped spin-valves. The pulse
durations leading to switching follow a comb-like distribution, multiply-peaked
at a few most probable, regularly spaced switching durations. These durations
reflect the precessional nature of the switching, which occurs through a
fluctuating integer number of precession cycles. This can be modeled
considering the thermal variance of the initial magnetization orientations and
the occurrence of vanishing total torque in the possible magnetization
trajectories. Biasing the spin-valve with a hard axis field prevents some of
these occurrences, and can provide an almost perfect reproducibility of the
switching duration.Comment: submitted to PR
Study of the Proton Single-Particle Strengths in 19F and Proton Shell Closure of 18O through the 18O(d, n)19F Reaction
開始ページ、終了ページ: 冊子体のページ付
Single-Proton Strengths in 19F Through the (d, n) Reaction at 25 MeV
開始ページ、終了ページ: 冊子体のページ付
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