696 research outputs found
Prospect for antiferromagnetic spintronics
Exploiting both spin and charge of the electron in electronic micordevices
has lead to a tremendous progress in both basic condensed-matter research and
microelectronic applications, resulting in the modern field of spintronics.
Current spintronics relies primarily on ferromagnets while antiferromagnets
have traditionally played only a supporting role. Recently, antiferromagnets
have been revisited as potential candidates for the key active elements in
spintronic devices. In this paper we review approaches that have been employed
for reading, writing, and storing information in antiferromagnets
Resistance spikes and domain wall loops in Ising quantum Hall ferromagnets
We explain the recent observation of resistance spikes and hysteretic
transport properties in Ising quantum Hall ferromagnets in terms of the unique
physics of their domain walls. Self-consistent RPA/Hartree-Fock theory is
applied to microscopically determine properties of the ground state and
domain-wall excitations. In these systems domain wall loops support
one-dimensional electron systems with an effective mass comparable to the bare
electron mass and may carry charge. Our theory is able to account
quantitatively for the experimental Ising critical temperature and to explain
characteristics of the resistive hysteresis loops.Comment: 4 pages, 3 figure
In-Plane Magnetic Field Induced Anisotropy of 2D Fermi Contours and the Field Dependent Cyclotron Mass
The electronic structure of a 2D gas subjected to a tilted magnetic field,
with a strong component parallel to the GaAs/AlGaAs interface and a weak
component oriented perpendicularly, is studied theoretically. It is shown that
the parallel field component modifies the originally circular shape of a Fermi
contour while the perpendicular component drive an electron by the Lorentz
force along a Fermi line with a cyclotron frequency given by its shape. The
corresponding cyclotron effective mass is calculated self-consistently for
several concentrations of 2D carriers as a function of the in-plane magnetic
field. The possibility to detect its field-induced deviations from the zero
field value experimentally is discussed.Comment: written in LaTeX, 9 pages, 4 figures (6 pages) in 1 PS file
(compressed and uuencoded) available on request from [email protected],
SM-JU-93-
Effect of inversion asymmetry on the intrinsic anomalous Hall effect in ferromagnetic (Ga,Mn)As
The relativistic nature of the electron motion underlies the intrinsic part
of the anomalous Hall effect, believed to dominate in ferromagnetic (Ga,Mn)As.
In this paper, we concentrate on the crystal band structure as an important
facet to the description of this phenomenon. Using different k.p and
tight-binding computational schemes, we capture the strong effect of the bulk
inversion asymmetry on the Berry curvature and the anomalous Hall conductivity.
At the same time, we find it not to affect other important characteristics of
(Ga,Mn)As, namely the Curie temperature and uniaxial anisotropy fields. Our
results extend the established theories of the anomalous Hall effect in
ferromagnetic semiconductors and shed new light on its puzzling nature
Manifestation of the spin-Hall effect through transport measurements in the mesoscopic regime
We study theoretically the manifestation of the spin-Hall effect in a
two-dimensional electronic system with Rashba spin-orbit coupling via
dc-transport measurements in realistic mesoscopic H-shape structures. The
Landauer-Buttiker formalism is used to model samples with mobilities and Rashba
coupling strengths of current experiments and to demonstrate the appearance of
a measurable Rashba-coupling dependent voltage. This type of measurement
requires only metal contacts, i.e., no magnetic elements are present. We also
confirm the robustness of the intrinsic spin-Hall effect against disorder in
the mesoscopic metallic regime in agreement with results of exact
diagonalization studies in the bulk.Comment: 5 pages, 3 figure
Charge Hall effect driven by spin-dependent chemical potential gradients and Onsager relations in mesoscopic systems
We study theoretically the spin-Hall effect as well as its reciprocal
phenomenon (a transverse charge current driven by a spin-dependent chemical
potential gradient) in electron and hole finite size mesoscopic systems. The
Landauer-Buttiker-Keldysh formalism is used to model samples with mobilities
and Rashba coupling strengths which are experimentally accessible and to
demonstrate the appearance of measurable charge currents induced by the
spin-dependent chemical potential gradient in the reciprocal spin-Hall effect.
We also demonstrate that within the mesoscopic coherent transport regime the
Onsager relations are fulfilled for the disorder averaged conductances for
electron and hole mesoscopic systems.Comment: 5 pages, 6 figures, typos correcte
Landau Level Anticrossing Manifestations in the Phase Diagram Topology of a Two Subband System
In a two-subband GaAs/AlGaAs two-dimensional electron system, the phase
diagram of longitudinal resistivity \rho_xx in density and magnetic field plane
exhibits an intriguing structure centered at filling factor \nu = 4 which is
strikingly different from the ring-like structures at lower magnetic fields.
Thermal activation measurements reveal an anticrossing gap on each boundary of
the structure where intersubband Landau Levels with parallel or antiparallel
spin are brought into degeneracy. While the physics of the anticrossing can be
ascribed to the pseudospin quantum Hall ferromagnetism, as reported earlier by
Muraki et al, the mapping and modeling of the phase diagram topology allow us
to establish a more complete picture of the consequences of real spin /
pseudo-spin interactions for the two subband system.Comment: Accepted by Physical Review
Writing and Reading antiferromagnetic MnAu: N\'eel spin-orbit torques and large anisotropic magnetoresistance
Antiferromagnets are magnetically ordered materials which exhibit no net
moment and thus are insensitive to magnetic fields. Antiferromagnetic
spintronics aims to take advantage of this insensitivity for enhanced
stability, while at the same time active manipulation up to the natural THz
dynamic speeds of antiferromagnets is possible, thus combining exceptional
storage density and ultra-fast switching. However, the active manipulation and
read-out of the N\'eel vector (staggered moment) orientation is challenging.
Recent predictions have opened up a path based on a new spin-orbit torque,
which couples directly to the N\'eel order parameter. This N\'eel spin-orbit
torque was first experimentally demonstrated in a pioneering work using
semimetallic CuMnAs. Here we demonstrate for MnAu, a good conductor with a
high ordering temperature suitable for applications, reliable and reproducible
switching using current pulses and readout by magnetoresistance measurements.
The symmetry of the torques agrees with theoretical predictions and a large
read-out magnetoresistance effect of more than ~ is reproduced by
ab initio transport calculations.Comment: 5 pages, 4 figure
High antiferromagnetic domain wall velocity induced by Néel spin-orbit torques
We demonstrate the possibility to drive an antiferromagnetic domain wall at high velocities by fieldlike Néel spin-orbit torques. Such torques arise from current-induced local fields that alternate their orientation on each sublattice of the antiferromagnet and whose orientation depends primarily on the current direction, giving them their fieldlike character. The domain wall velocities that can be achieved by this mechanism are 2 orders of magnitude greater than the ones in ferromagnets. This arises from the efficiency of the staggered spin-orbit fields to couple to the order parameter and from the exchange-enhanced phenomena in
antiferromagnetic texture dynamics, which leads to a low domain wall effective mass and the absence of a Walker breakdown limit. In addition, because of its nature, the staggered spin-orbit field can lift the degeneracy between two 180° rotated states in a collinear antiferromagnet, and it provides a force that can move such walls and control the switching of the states
- …