1,241 research outputs found
Numerical Investigation on Asymmetric Bilayer System at Integer Filling Factor
Deformation of the easy-axis ferromagnetic state in asymmetric bilayer
systems are investigated numerically. Using the exact diagonalization the
easy-axis to easy-plane ferromagnetic transition at total filling factor 3 or 4
is investigated. At still higher filling, novel stripe state in which stripes
are aligned in the vertical direction occurs. The Hartree-Fock energies of
relevant ordered states are calculated and compared.Comment: 4 pages, 6 figures, Proceedings of EP2DS-15, to appear in Physica
Interlayer exchange coupling in (Ga,Mn)As based multilayers
Exhibiting antiferromagnetic interlayer coupling in dilute magnetic
semiconductor multilayers is essential for the realisation of
magnetoresistances analogous to giant magnetoresistance in metallic multilayer
structures. In this work we use a mean-field theory of carrier induced
ferromagnetism to explore possible (Ga,Mn)As based multilayer structures that
might yield antiferromagnetic coupling.Comment: 4 pages, 2 figures. To be published in physica status solidi c as the
proceedings of the PASPS IV conferenc
Non-vanishing spin Hall currents in disordered spin-orbit coupling systems
Spin currents that flow perpendicular to the electric field direction are
generic in metals and doped semiconductors with spin-orbit coupling. It has
recently been argued that the spin Hall conductivity can be dominated by an
intrinsic contribution which follows from Bloch state distortion in the
presence of an electric field. Here we report on an numerical demonstration of
the robustness of this effect in the presence of disorder scattering for the
case of a two-dimensional electron-gas with Rashba spin-orbit interactions
(R2DES).Comment: 4 pages, 3 figure
Infrared magneto-optical properties of (III,Mn)V ferromagetic semiconductors
We present a theoretical study of the infrared magneto-optical properties of
ferromagnetic (III,Mn)V semiconductors. Our analysis combines the kinetic
exchange model for (III,Mn)V ferromagnetism with Kubo linear response theory
and Born approximation estimates for the effect of disorder on the valence band
quasiparticles. We predict a prominent feature in the ac-Hall conductivity at a
frequency that varies over the range from 200 to 400 meV, depending on Mn and
carrier densities, and is associated with transitions between heavy-hole and
light-hole bands. In its zero frequency limit, our Hall conductivity reduces to
the -space Berry's phase value predicted by a recent theory of the
anomalous Hall effect that is able to account quantitatively for experiment. We
compute theoretical estimates for magnetic circular dichroism, Faraday
rotation, and Kerr effect parameters as a function of Mn concentration and free
carrier density. The mid-infrared response feature is present in each of these
magneto-optical effects.Comment: 11 pages, 5 figure
Mn incorporation in as-grown and annealed (Ga,Mn)As layers studied by x-ray diffraction and standing-wave uorescence
A combination of high-resolution x-ray diffraction and a new technique of
x-ray standing wave uorescence at grazing incidence is employed to study the
structure of (Ga,Mn)As diluted magnetic semiconductor and its changes during
post-growth annealing steps. We find that the film is formed by a uniform,
single crystallographic phase epilayer covered by a thin surface layer with
enhanced Mn concentration due to Mn atoms at random non-crystallographic
positions. In the epilayer, Mn incorporated at interstitial position has a
dominant effect on lattice expansion as compared to substitutional Mn. The
expansion coeffcient of interstitial Mn estimated from our data is consistent
with theory predictions. The concentration of interstitial Mn and the
corresponding lattice expansion of the epilayer are reduced by annealing,
accompanied by an increase of the density of randomly distributed Mn atoms in
the disordered surface layer. Substitutional Mn atoms remain stable during the
low-temperature annealing.Comment: 9 pages, 9 figure
Coherent control of magnetization precession in ferromagnetic semiconductor (Ga,Mn)As
We report single-color, time resolved magneto-optical measurements in
ferromagnetic semiconductor (Ga,Mn)As. We demonstrate coherent optical control
of the magnetization precession by applying two successive ultrashort laser
pulses. The magnetic field and temperature dependent experiments reveal the
collective Mn-moment nature of the oscillatory part of the time-dependent Kerr
rotation, as well as contributions to the magneto-optical signal that are not
connected with the magnetization dynamics.Comment: 6 pages, 3 figures, accepted in Applied Physics Letter
Fast optical control of spin in semiconductor interfacial structures
We report on a picosecond-fast optical removal of spin polarization from a
self-confined photo-carrier system at an undoped GaAs/AlGaAs interface
possessing superior long-range and high-speed spin transport properties. We
employed a modified resonant spin amplification technique with unequal
intensities of subsequent pump pulses to experimentally distinguish the
evolution of spin populations originating from different excitation laser
pulses. We demonstrate that the density of spins, which is injected into the
system by means of the optical orientation, can be controlled by reducing the
electrostatic confinement of the system using an additional generation of
photocarriers. It is also shown that the disturbed confinement recovers within
hundreds of picoseconds after which spins can be again photo-injected into the
system
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