24,427 research outputs found
Surface spin flip probability of mesoscopic Ag wires
Spin relaxation in mesoscopic Ag wires in the diffusive transport regime is
studied via nonlocal spin valve and Hanle effect measurements performed on
permalloy/Ag lateral spin valves. The ratio between momentum and spin
relaxation times is not constant at low temperatures. This can be explained
with the Elliott-Yafet spin relaxation mechanism by considering the momentum
surface relaxation time as being temperature dependent. We present a model to
separately determine spin flip probabilities for phonon, impurity and surface
scattering and find that the spin flip probability is highest for surface
scattering.Comment: 5 pages, 4 figure
Dynamics of polymer bridge formation and disruption
In this Letter we show, with colloidal probe AFM measurements, that the formation and subsequent disruption of polymer bridges between two solid surfaces is characterized by slow relaxation times. This is due to the retardation of polymer dynamics near a surface. For colloidal particles, that are in constant (Brownian) motion, kinetic aspects are key. To understand these effects, we develop a model of polymer bridging and bridge disruption that agrees quantitatively with our experiment
Detection and quantification of inverse spin Hall effect from spin pumping in permalloy/normal metal bilayers
Spin pumping is a mechanism that generates spin currents from ferromagnetic
resonance (FMR) over macroscopic interfacial areas, thereby enabling sensitive
detection of the inverse spin Hall effect that transforms spin into charge
currents in non-magnetic conductors. Here we study the spin-pumping-induced
voltages due to the inverse spin Hall effect in permalloy/normal metal bilayers
integrated into coplanar waveguides for different normal metals and as a
function of angle of the applied magnetic field direction, as well as microwave
frequency and power. We find good agreement between experimental data and a
theoretical model that includes contributions from anisotropic
magnetoresistance (AMR) and inverse spin Hall effect (ISHE). The analysis
provides consistent results over a wide range of experimental conditions as
long as the precise magnetization trajectory is taken into account. The spin
Hall angles for Pt, Pd, Au and Mo were determined with high precision to be
, , and ,
respectively.Comment: 11 page
Quantifying spin Hall angles from spin pumping: Experiments and Theory
Spin Hall effects intermix spin and charge currents even in nonmagnetic
materials and, therefore, ultimately may allow the use of spin transport
without the need for ferromagnets. We show how spin Hall effects can be
quantified by integrating permalloy/normal metal (N) bilayers into a coplanar
waveguide. A dc spin current in N can be generated by spin pumping in a
controllable way by ferromagnetic resonance. The transverse dc voltage detected
along the permalloy/N has contributions from both the anisotropic
magnetoresistance (AMR) and the spin Hall effect, which can be distinguished by
their symmetries. We developed a theory that accounts for both. In this way, we
determine the spin Hall angle quantitatively for Pt, Au and Mo. This approach
can readily be adapted to any conducting material with even very small spin
Hall angles.Comment: 4 pages, 4 figure
Running coupling and mass anomalous dimension of SU(3) gauge theory with two flavors of symmetric-representation fermions
We have measured the running coupling constant of SU(3) gauge theory coupled
to Nf=2 flavors of symmetric representation fermions, using the Schrodinger
functional scheme. Our lattice action is defined with hypercubic smeared links
which, along with the larger lattice sizes, bring us closer to the continuum
limit than in our previous study. We observe that the coupling runs more slowly
than predicted by asymptotic freedom, but we are unable to observe fixed point
behavior before encountering a first order transition to a strong coupling
phase. This indicates that the infrared fixed point found with the thin-link
action is a lattice artifact. The slow running of the gauge coupling permits an
accurate determination of the mass anomalous dimension for this theory, which
we observe to be small, gamma_m < 0.6, over the range of couplings we can
reach. We also study the bulk and finite-temperature phase transitions in the
strong coupling region.Comment: 17 pages, 16 figures. Substantial modifications to explain why the
fat-link result for the beta function supersedes our thin-link result; also
updated the phase diagram to reflect additional numerical work. Added
references. Final versio
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