2,034 research outputs found
Spin-torque efficiency enhanced by Rashba spin splitting in three dimensions
We examine a spin torque induced by the Rashba spin-orbit coupling in three
dimensions within the Boltzmann transport theory. We analytically calculate the
spin torque and show how its behavior is related with the spin topology in the
Fermi surfaces by studying the Fermi-energy dependence of the spin torque.
Moreover we discuss the spin-torque efficiency which is the spin torque divided
by the applied electric current in association with the current-induced
magnetization reversal. It is found that high spin-torque efficiency is
achieved when the Fermi energy lies on only the lower band and there exists an
optimal value for the Rashba parameter, where the spin-torque efficiency
becomes maximum.Comment: 7 pages, 5 figure
High domain wall velocities induced by current in ultrathin Pt/Co/AlOx wires with perpendicular magnetic anisotropy
Current-induced domain wall (DW) displacements in an array of ultrathin
Pt/Co/AlOx wires with perpendicular magnetic anisotropy have been directly
observed by wide field Kerr microscopy. DWs in all wires in the array were
driven simultaneously and their displacement on the micrometer-scale was
controlled by the current pulse amplitude and duration. At the lower current
densities where DW displacements were observed (j less than or equal to 1.5 x
10^12 A/m^2), the DW motion obeys a creep law. At higher current density (j =
1.8 x 10^12 A/m^2), zero-field average DW velocities up to 130 +/- 10 m/s were
recorded.Comment: Minor changes to Fig. 1(b) and text, correcting for the fact that
domain walls were subsequently found to move counter to the electron flow.
References update
Domain wall tilting in the presence of the Dzyaloshinskii-Moriya interaction in out-of-plane magnetized magnetic nanotracks
We show that the Dzyaloshinskii-Moriya interaction (DMI) can lead to a
tilting of the domain wall (DW) surface in perpendicularly magnetized magnetic
nanotracks when DW dynamics is driven by an easy axis magnetic field or a spin
polarized current. The DW tilting affects the DW dynamics for large DMI and the
tilting relaxation time can be very large as it scales with the square of the
track width. The results are well explained by an analytical model based on a
Lagrangian approach where the DMI and the DW tilting are included. We propose a
simple way to estimate the DMI in a magnetic multilayers by measuring the
dependence of the DW tilt angle on a transverse static magnetic field. Our
results shed light on the current induced DW tilting observed recently in Co/Ni
multilayers with inversion asymmetry, and further support the presence of DMI
in these systems.Comment: 12 pages, 3 figures, 1 Supplementary Material
Locally Anisotropic Structures and Nonlinear Connections in Einstein and Gauge Gravity
We analyze local anisotropies induced by anholonomic frames and associated
nonlinear connections in general relativity and extensions to affine Poincare
and de Sitter gauge gravity and different types of Kaluza-Klein theories. We
construct some new classes of cosmological solutions of gravitational field
equations describing Friedmann-Robertson-Walker like universes with rotation
(ellongated and flattened) ellipsoidal or torus symmetry.Comment: 37 page
Prevention and extinguishment of fires involving hypergolic propellants Final report
Halon 1301 system effectiveness in prevention and extinguishment of hypergolic propellant fire
Electric-field control of domain wall nucleation and pinning in a metallic ferromagnet
The electric (E) field control of magnetic properties opens the prospects of
an alternative to magnetic field or electric current activation to control
magnetization. Multilayers with perpendicular magnetic anisotropy (PMA) have
proven to be particularly sensitive to the influence of an E-field due to the
interfacial origin of their anisotropy. In these systems, E-field effects have
been recently applied to assist magnetization switching and control domain wall
(DW) velocity. Here we report on two new applications of the E-field in a
similar material : controlling DW nucleation and stopping DW propagation at the
edge of the electrode
Interatomic scattering in energy dependent photoelectron spectra of Ar clusters
Soft X-ray photoelectron spectra of Ar 2p levels of atomic argon and argon
clusters are recorded over an extended range of photon energies. The Ar 2p
intensity ratios between atomic argon and clusters’ surface and bulk
components reveal oscillations similar to photoelectron extended X-ray
absorption fine structure signal (PEXAFS). We demonstrate here that this
technique allows us to analyze separately the PEXAFS signals from surface and
bulk sites of free-standing, neutral clusters, revealing a bond contraction at
the surface
Finsler and Lagrange Geometries in Einstein and String Gravity
We review the current status of Finsler-Lagrange geometry and
generalizations. The goal is to aid non-experts on Finsler spaces, but
physicists and geometers skilled in general relativity and particle theories,
to understand the crucial importance of such geometric methods for applications
in modern physics. We also would like to orient mathematicians working in
generalized Finsler and Kahler geometry and geometric mechanics how they could
perform their results in order to be accepted by the community of ''orthodox''
physicists.
Although the bulk of former models of Finsler-Lagrange spaces where
elaborated on tangent bundles, the surprising result advocated in our works is
that such locally anisotropic structures can be modelled equivalently on
Riemann-Cartan spaces, even as exact solutions in Einstein and/or string
gravity, if nonholonomic distributions and moving frames of references are
introduced into consideration.
We also propose a canonical scheme when geometrical objects on a (pseudo)
Riemannian space are nonholonomically deformed into generalized Lagrange, or
Finsler, configurations on the same manifold. Such canonical transforms are
defined by the coefficients of a prime metric and generate target spaces as
Lagrange structures, their models of almost Hermitian/ Kahler, or nonholonomic
Riemann spaces.
Finally, we consider some classes of exact solutions in string and Einstein
gravity modelling Lagrange-Finsler structures with solitonic pp-waves and
speculate on their physical meaning.Comment: latex 2e, 11pt, 44 pages; accepted to IJGMMP (2008) as a short
variant of arXiv:0707.1524v3, on 86 page
The nature of domain walls in ultrathin ferromagnets revealed by scanning nanomagnetometry
The recent observation of current-induced domain wall (DW) motion with large
velocity in ultrathin magnetic wires has opened new opportunities for
spintronic devices. However, there is still no consensus on the underlying
mechanisms of DW motion. Key to this debate is the DW structure, which can be
of Bloch or N\'eel type, and dramatically affects the efficiency of the
different proposed mechanisms. To date, most experiments aiming to address this
question have relied on deducing the DW structure and chirality from its motion
under additional in-plane applied fields, which is indirect and involves strong
assumptions on its dynamics. Here we introduce a general method enabling
direct, in situ, determination of the DW structure in ultrathin ferromagnets.
It relies on local measurements of the stray field distribution above the DW
using a scanning nanomagnetometer based on the Nitrogen-Vacancy defect in
diamond. We first apply the method to a Ta/Co40Fe40B20(1 nm)/MgO magnetic wire
and find clear signature of pure Bloch DWs. In contrast, we observe left-handed
N\'eel DWs in a Pt/Co(0.6 nm)/AlOx wire, providing direct evidence for the
presence of a sizable Dzyaloshinskii-Moriya interaction (DMI) at the Pt/Co
interface. This method offers a new path for exploring interfacial DMI in
ultrathin ferromagnets and elucidating the physics of DW motion under current.Comment: Main text and Supplementary Information, 33 pages and 12 figure
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