1,286 research outputs found
Electronic structure of InMnAs studied by photoemission spectroscopy: Comparison with GaMnAs
We have investigated the electronic structure of the -type diluted
magnetic semiconductor InMnAs by photoemission spectroscopy. The Mn
3 partial density of states is found to be basically similar to that of
GaMnAs. However, the impurity-band like states near the top of
the valence band have not been observed by angle-resolved photoemission
spectroscopy unlike GaMnAs. This difference would explain the
difference in transport, magnetic and optical properties of
InMnAs and GaMnAs. The different electronic
structures are attributed to the weaker Mn 3 - As 4 hybridization in
InMnAs than in GaMnAs.Comment: 4 pages, 3 figure
Generality of rotating partial cavitation in two-dimensional cascades
Numerical simulations of 2-dimensional (2D) unsteady cavitating flows were carried out under various conditions of the number of blades, incidence angles and cavitation numbers. When the incidence angle increased or the cavitation number decreased, the steady balanced cavitation transited to unsteady and non-uniform patterns. Typical patterns reported in the previous studies such as rotating, asymmetric and alternating for 3- and 4-blades were successfully reproduced. In this study, cascades of the larger number of blades were dealt with to consider the generality of unsteadiness by reducing the influence of periodicity. The cavitation is basically triggered in the backward next section. However, the period of time for growing causes complexity in the discrimination of propagation. In most cases of rotating partial cavitation, except for 4-blades, the cavity develops in the second passage of backward direction after the decay of largest cavity. In case of many blades, multiple cavities rotate simultaneously and the particular patterns observed in cascades of small even numbers of blades attenuate.http://deepblue.lib.umich.edu/bitstream/2027.42/84276/1/CAV2009-final90.pd
Influence of band structure effects on domain-wall resistance in diluted ferromagnetic semiconductors
Intrinsic domain-wall resistance (DWR) in (Ga,Mn)As is studied theoretically
and compared to experimental results. The recently developed model of spin
transport in diluted ferromagnetic semiconductors [Van Dorpe et al., Phys. Rev.
B 72, 205322 (2005)] is employed. The model combines the disorder-free
Landauer-B\"uttiker formalism with the tight-binding description of the host
band structure. The obtained results show how much the spherical 4x4 kp model
[Nguyen, Shchelushkin, and Brataas, cond-mat/0601436] overestimates DWR in the
adiabatic limit, and reveal the dependence of DWR on the magnetization profile
and crystallographic orientation of the wall.Comment: 4 pages, 4 figures, submitted to Phys. Rev. B - Rapid Com
Mechanism of carrier-induced ferromagnetism in magnetic semiconductors
Taking into account both random impurity distribution and thermal
fluctuations of localized spins, we have performed a model calculation for the
carrier (hole) state in GaMnAs by using the coherent potential
approximation (CPA). The result reveals that a {\it p}-hole in the band tail of
GaMnAs is not like a free carrier but is rather virtually bounded
to impurity sites. The carrier spin strongly couples to the localized {\it d}
spins on Mn ions. The hopping of the carrier among Mn sites causes the
ferromagnetic ordering of the localized spins through the double-exchange
mechanism. The Curie temperature obtained by using conventional parameters
agrees well with the experimental result.Comment: 7 pages, 4 figure
Theoretical models of ferromagnetic III-V semiconductors
Recent materials research has advanced the maximum ferromagnetic transition
temperature in semiconductors containing magnetic elements toward room
temperature. Reaching this goal would make information technology applications
of these materials likely. In this article we briefly review the status of work
over the past five years which has attempted to achieve a theoretical
understanding of these complex magnetic systems. The basic microscopic origins
of ferromagnetism in the (III,Mn)V compounds that have the highest transition
temperatures appear to be well understood, and efficient computation methods
have been developed which are able to model their magnetic, transport, and
optical properties. However many questions remain.Comment: 4 pages, 4 figures, review, to be published in Curr. Appl. Phy
Spin-dependent tunneling in modulated structures of (Ga,Mn)As
A model of coherent tunneling, which combines multi-orbital tight-binding
approximation with Landauer-B\"uttiker formalism, is developed and applied to
all-semiconductor heterostructures containing (Ga,Mn)As ferromagnetic layers. A
comparison of theoretical predictions and experimental results on
spin-dependent Zener tunneling, tunneling magnetoresistance (TMR), and
anisotropic magnetoresistance (TAMR) is presented. The dependence of spin
current on carrier density, magnetization orientation, strain, voltage bias,
and spacer thickness is examined theoretically in order to optimize device
design and performance.Comment: 9 pages, 13 figures, submitted to PR
Interlayer Exchange Coupling in (Ga,Mn)As-based Superlattices
The interlayer coupling between (Ga,Mn)As ferromagnetic layers in
all-semiconductor superlattices is studied theoretically within a tight-binding
model, which takes into account the crystal, band and magnetic structure of the
constituent superlattice components. It is shown that the mechanism originally
introduced to describe the spin correlations in antiferromagnetic EuTe/PbTe
superlattices, explains the experimental results observed in ferromagnetic
semiconductor structures, i.e., both the antiferromagnetic coupling between
ferromagnetic layers in IV-VI (EuS/PbS and EuS/YbSe) superlattices as well as
the ferromagnetic interlayer coupling in III-V ((Ga,Mn)As/GaAs) multilayer
structures. The model allows also to predict (Ga,Mn)As-based structures, in
which an antiferromagnetic interlayer coupling could be expected.Comment: 4 pages, 3 figure
Electrospray ionization mass spectrometric observation of ligand exchange of zinc pyrithione with amino acids
ArticleRAPID COMMUNICATIONS IN MASS SPECTROMETRY. 23(14):2161-2166 (2009)journal articl
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