9,836 research outputs found
Influence of complex disorder on skew-scattering Hall effects in -ordered FePt alloy
We show by first-principles calculations that the skew-scattering anomalous
Hall and spin-Hall angles of L-ordered FePt drastically depend on
different types of disorder. A different sign of the AHE is obtained when
slightly deviating from the stoichiometric ratio towards the Fe-rich side as
compared to the Pt-rich side. For stoichiometric samples, short-range ordering
of defects has a profound effect on the Hall angles and can change them by a
factor of as compared to the case of uncorrelated disorder. This might
explain the vast range of anomalous Hall angles measured in experiments, which
undergo different preparation procedures and thus might differ in their
crystallographic quality
Spin-flip hot spots in ultrathin films of monovalent metals: Enhancement and anisotropy of the Elliott-Yafet parameter
In contrast to the long-known fact that spin-flip hot spots, i.e., special
\vc{k}-points on the Fermi surface showing a high spin-mixing parameter, do not
occur in the bulk of monovalent (noble and alkali) metals, we found them on the
surface Brillouin-zone boundary of ultrathin films of these metals.
Density-functional calculations within the Korringa-Kohn-Rostoker Green
function method for ultrathin (001) oriented Cu, Ag, and Au films of 10-layer
thickness show that the region around the hot spots can have a substantial
contribution, e.g.\ 52\% in Au(001), to the integrated spin-mixing parameter,
that could lead to a significant enhancement of the spin-relaxation rate or
spin-Hall angle in thin films. Owing to the appearance of spin-flip hot-spots,
a large anisotropy of the Elliott-Yafet parameter [50\% for Au(001)] is also
found in these systems. The findings are important for spintronics applications
in which noble-metals are frequently used and in which the dimensionality of
the sample is reduced.Comment: 6 pages, 2 figure
Spin relaxation and spin Hall transport in 5d transition-metal ultrathin films
The spin relaxation induced by the Elliott-Yafet mechanism and the extrinsic
spin Hall conductivity due to the skew-scattering are investigated in 5d
transition-metal ultrathin films with self-adatom impurities as scatterers. The
values of the Elliott-Yafet parameter and of the spin-flip relaxation rate
reveal a correlation with each other that is in agreement with the Elliott
approximation. At 10-layer thickness, the spin-flip relaxation time in 5d
transition-metal films is quantitatively reported about few hundred nanoseconds
at atomic percent which is one and two orders of magnitude shorter than that in
Au and Cu thin films, respectively. The anisotropy effect of the Elliott-Yafet
parameter and of the spin-flip relaxation rate with respect to the direction of
the spin-quantization axis in relation to the crystallographic axes is also
analyzed. We find that the anisotropy of the spin-flip relaxation rate is
enhanced due to the Rashba surface states on the Fermi surface, reaching values
as high as 97% in 10-layer Hf(0001) film or 71% in 10-layer W(110) film.
Finally, the spin Hall conductivity as well as the spin Hall angle due to the
skew-scattering off self-adatom impurities are calculated using the Boltzmann
approach. Our calculations employ a relativistic version of the
first-principles full-potential Korringa-Kohn-Rostoker Green function method
Evolution of Nuclear Shell Structure due to the Pion Exchange Potential
The evolution of nuclear shell structure is investigated for the first time
within density-dependent relativistic Hartree-Fock theory and the role of
-exchange potential is studied in detail. The energy differences between
the neutron orbits \Lrb{\nu1h_{9/2},\nu 1i_{13/2}} in the N=82 isotones and
between the proton ones \Lrb{\pi1g_{7/2},\pi1h_{11/2}} in the Z=50 isotopes
are extracted as a function of neutron excess . A kink around for
the N=82 isotones is found as an effect resulting from pion correlations. It is
shown that the inclusion of -coupling plays a central role to provide
realistic isospin dependence of the energy differences. In particular, the
tensor part of the -coupling has an important effect on the characteristic
isospin dependence observed in recent experiments.Comment: 4 pages and 4 figure
Non-local field-like spin-orbit torques in Rashba systems: an ab-initio study of AgBi/Ag/Fe film
We investigate from first principles the field-like spin-orbit torques (SOTs)
in a AgBi-terminated Ag(111) film grown on ferromagnetic Fe(110). We find
that a large part of the SOT arises from the spin-orbit interaction (SOI) in
the AgBi layer far away from the Fe layers. These results clearly hint at
a long range spin transfer in the direction perpendicular to the film that does
not originate in the spin Hall effect. In order to bring evidence of the
non-local character of the computed SOT, we show that the torque acting on the
Fe layers can be engineered by the introduction of Bi vacancies in the
AgBi layer. Overall, we find a drastic dependence of the SOT on the
disorder type, which we explain by a complex interplay of different
contributions to the SOT in the Brillouin zone
Strong spin-orbit fields and Dyakonov-Perel spin dephasing in supported metallic films
Spin dephasing by the Dyakonov-Perel mechanism in metallic films deposited on
insulating substrates is revealed, and quantitatively examined by means of
density functional calculations combined with a kinetic equation. The
surface-to-substrate asymmetry, probed by the metal wave functions in thin
films, is found to produce strong spin-orbit fields and a fast Larmor
precession, giving a dominant contribution to spin decay over the Elliott-Yafet
spin relaxation up to a thickness of 70 nm. The spin dephasing is oscillatory
in time with a rapid (sub-picosecond) initial decay. However, parts of the
Fermi surface act as spin traps, causing a persistent tail signal lasting 1000
times longer than the initial decay time. It is also found that the decay
depends on the direction of the initial spin polarization, resulting in a
spin-dephasing anisotropy of 200% in the examined cases
The Higgs Sector of the Minimal 3 3 1 Model Revisited
The mass spectrum and the eigenstates of the Higgs sector of the minimal 3 3
1 model are revisited in detail. There are discrepancies between our results
and previous results by another author.Comment: 20 pages, latex, two figures. One note and one reference are adde
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