1,580 research outputs found
Influence Of Current Leads On Critical Current For Spin Precession In Magnetic Multilayers
In magnetic multilayers, a dc current induces a spin precession above a
certain critical current. Drive torques responsible for this can be calculated
from the spin accumulation . Existing calculations of
assume a uniform cross section of conductors. But most
multilayer samples are pillars with current leads flaring out immediately to a
much wider cross-section area than that of the pillar itself. We write
spin-diffusion equations of a form valid for variable cross section, and solve
the case of flat electrodes with radial current distribution perpendicular to
the axis of the pillar. Because of the increased volume available for
conduction-electron spin relaxation in such leads, is reduced
in the pillar by at least a factor of 2 below its value for uniform cross
section, for given current density in the pillar. Also, and
the critical current density for spin precession become nearly independent of
the thickness of the pinned magnetic layer, and more dependent on the thickness
of the spacer, in better agreement with measurements by Albert et al. (2002).Comment: To appear in J. Magn. Magn. Mate
Optical far-infrared properties of graphene monolayer and multilayers
We analyze the features of the graphene mono- and multilayer reflectance in
the far-infrared region as a function of frequency, temperature, and carrier
density taking the intraband conductance and the interband electron absorbtion
into account. The dispersion of plasmon mode of the multilayers is calculated
using Maxwell's equations with the influence of retardation included. At low
temperatures and high electron densities, the reflectance of multilayers as a
function of frequency has the sharp downfall and the subsequent deep well due
to the threshold of electron interband absorbtion.Comment: 9 pages, 4 figure
Current-induced spin-wave excitations in a single ferromagnetic layer
A new current induced spin-torque transfer effect has been observed in a
single ferromagnetic layer without resorting to multilayers. At a specific
current density of one polarity injected from a point contact, abrupt
resistance changes due to current-induced spin wave excitations have been
observed. The critical current at the onset of spin-wave excitations depends
linearly on the external field applied perpendicular to the layer. The observed
effect is due to current-driven heterogeneity in an otherwise uniform
ferromagnetic layer.Comment: 12 pages, 4 figure
Current-Induced Magnetization Reversal in High Magnetic Fields in Co/Cu/Co Nanopillars
Current-induced magnetization dynamics in Co/Cu/Co trilayer nanopillars
(~100nm in diameter) has been studied experimentally for large applied fields
perpendicular to the layers. An abrupt and hysteretic increase in dynamic
resistance is observed at high current densities for one polarity of the
current, comparable to the giant magnetoresistance effect observed at low
fields. A micromagnetic model, that includes a spin-transfer torque, suggests
that the current induces a complete reversal of the thin Co layer to alignment
antiparallel to the applied field-that is, to a state of maximum magnetic
energy.Comment: 11 pages, 3 figures, (submitted to Phys. Rev. Lett.), added missing
figure caption of fig. 3, updated to published versio
Effect of Antiferromagnetic Interlayer Coupling on Current-Assisted Magnetization Switching
We compare magnetization switching in Co/Cu/Co nanopillars with uncoupled and
dipole-field coupled Co layers. In uncoupled nanopillars, current-driven
switching is hysteretic at low magnetic field H and changes to reversible,
characterized by telegraph noise, at high H. We show that dipolar coupling both
affects the switching current and causes the switching to become reversible at
small H. The coupling thus changes the switching to reversible, hysteretic, and
then reversible again as H increases. We describe our results in terms of
current-assisted thermal activation.Comment: 3 pages, 3 figure
Dynamics of Domain Wall in a Biaxial Ferromagnet With Spin-torque
The dynamics of the domain wall (DW) in a biaxial ferromagnet interacting
with a spin-polarized current are described by sine-gordon (SG) equation
coupled with Gilbert damping term in this paper. Within our frame-work of this
model, we obtain a threshold of the current in the motion of a single DW with
the perturbation theory on kink soliton solution to the corresponding
ferromagnetic system, and the threshold is shown to be dependent on the Gilbert
damping term. Also, the motion properties of the DW are discussed for the zero-
and nonzero-damping cases, which shows that our theory to describe the dynamics
of the DW are self-consistent.Comment: 7pages, 3figure
Temperature- and Bias-dependence of magnetoresistance in doped manganite thin film trilayer junctions
Thin film trilayer junction of LaSrMnO - SrTiO -
LaSrMnO shows a factor of 9.7 change in resistance, in a
magnetic field around 100 Oe at 14K. The junction magnetoresistance is bias and
temperature dependent. The energy scales associated with bias and temperature
dependence are an order of magnitude apart. The same set of energies also
determine the bias and temperature dependence of the differential conductance
of the junction. We discuss these results in terms of metallic cluster
inclusions at the junction-barrier interface.Comment: 3 pages, 4 figure
Relaxing-Precessional Magnetization Switching
A new way of magnetization switching employing both the spin-transfer torque
and the torque by a magnetic field is proposed. The solution of the
Landau-Lifshitz-Gilbert equation shows that the dynamics of the magnetization
in the initial stage of the switching is similar to that in the precessional
switching, while that in the final stage is rather similar to the relaxing
switching. We call the present method the relaxing-precessional switching. It
offers a faster and lower-power-consuming way of switching than the relaxing
switching and a more controllable way than the precessional switching
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