925 research outputs found
Comment on "Observation of Spin Injection at a Ferromagnet-Semiconductor Interface, by P.R. Hammar et al
In a recent Letter Hammar et al. claim the observation of injection of a
spin-polarized current in a two-dimensional electron gas (2DEG). This is an
important observation, since, despite considerable effort of several groups,
all attempts to realize spin-injection into a 2DEG using purely electrical
measurements have failed sofar. However, in my opinion the claim made is not
correct, and the observed behaviour can be explained by a combination of a
magneto resistance (Hall) effect (e.g. generated by the fringe magnetic fields
present at the edges of the ferromagnetic electrode), with a {\it
spin-independent} rectification effect due to the presence of a metal-
semiconductor junction.Comment: accepted for PRL, 1 pag
Music therapy supported the health-related quality of life for children undergoing haematopoietic stem cell transplants
Diffuse transport and spin accumulation in a Rashba two-dimensional electron gas
The Rashba Hamiltonian describes the splitting of the conduction band as a
result of spin-orbit coupling in the presence of an asymmetric confinement
potential and is commonly used to model the electronic structure of confined
narrow-gap semiconductors. Due to the mixing of spin states some care has to be
exercised in the calculation of transport properties. We derive the diffusive
conductance tensor for a disordered two-dimensional electron gas with
spin-orbit interaction and show that the applied bias induces a spin
accumulation, but that the electric current is not spin-polarized.Comment: REVTeX4 format, 5 page
The Magnetic Spin Ladder (C_{5}H_{12}N)_{2}CuBr_{4}: High Field Magnetization and Scaling Near Quantum Criticality
The magnetization, T, 0.7 K K), from single
crystals and powder samples of (CHN)CuBr has been used
to identify this system as an Heisenberg two-leg ladder in the strong
coupling limit, K and K, with T and T. An inflection point in K) at
half-saturation, , is described by an effective \emph{XXZ} chain. The
data exhibit universal scaling behavior in the vicinity of and
, indicating the system is near a quantum critical point.Comment: 4 pages, 4 figure
Spin Hall effect transistor
Spin transistors and spin Hall effects have been two separate leading
directions of research in semiconductor spintronics which seeks new paradigms
for information processing technologies. We have brought the two directions
together to realize an all-semiconductor spin Hall effect transistor. Our
scheme circumvents semiconductor-ferromagnet interface problems of the original
Datta-Das spin transistor concept and demonstrates the utility of the spin Hall
effects in microelectronics. The devices use diffusive transport and operate
without electrical current, i.e., without Joule heating in the active part of
the transistor. We demonstrate a spin AND logic function in a semiconductor
channel with two gates. Our experimental study is complemented by numerical
Monte Carlo simulations of spin-diffusion through the transistor channel.Comment: 11 pages, 3 figure
Neutron scattering from a coordination polymer quantum paramagnet
Inelastic neutron scattering measurements are reported for a powder sample of
the spin-1/2 quantum paramagnet . Magnetic neutron
scattering is identified above an energy gap of 1.9 meV. Analysis of the sharp
spectral maximum at the onset indicates that the material is magnetically
quasi-one-dimensional. Consideration of the wave vector dependence of the
scattering and polymeric structure further identifies the material as a
two-legged spin-1/2 ladder. Detailed comparison of the data to various models
of magnetism in this material based on the single mode approximation and the
continuous unitary transformation are presented. The latter theory provides an
excellent account of the data with leg exchange meV and
rung exchange meV.Comment: 10 pages, 11 figures, 1 tabl
Spin gap in the Quasi-One-Dimensional S=1/2 Antiferromagnet: Cu2(1,4-diazacycloheptane)2Cl4
Cu_{2}(1,4-diazacycloheptane)_{2}Cl_{4} contains double chains of spin 1/2
Cu^{2+} ions. We report ac susceptibility, specific heat, and inelastic neutron
scattering measurements on this material. The magnetic susceptibility,
, shows a rounded maximum at T = 8 K indicative of a low dimensional
antiferromagnet with no zero field magnetic phase transition. We compare the
data to exact diagonalization results for various one dimensional
spin Hamiltonians and find excellent agreement for a spin ladder with
intra-rung coupling meV and two mutually frustrating
inter-rung interactions: meV and meV. The
specific heat in zero field is exponentially activated with an activation
energy meV. A spin gap is also found through inelastic
neutron scattering on powder samples which identify a band of magnetic
excitations for meV. Using sum-rules we derive an
expression for the dynamic spin correlation function associated with
non-interacting propagating triplets in a spin ladder. The van-Hove
singularities of such a model are not observed in our scattering data
indicating that magnetic excitations in Cu_{2}(1,4-diazacycloheptane)_{2}Cl_{4}
are more complicated. For magnetic fields above T specific
heat data versus temperature show anomalies indicating a phase transition to an
ordered state below T = 1 K.Comment: 9 pages, 8 postscript figures, LaTeX, Submitted to PRB 8/4/97, e-mail
Comments to [email protected]
PCV29 Rates Of Acute Coronary Events And All Cause Mortality In Patients With Stable Coronary Artery Disease (Cad) After Myocardial Infarction And Additional Cardiovascular Risk Factors
Neutron Diffraction Study of the Pressure-Induced Magnetic Ordering in the Spin Gap System TlCuCl
Neutron elastic scattering measurements have been performed under the
hydrostatic pressure in order to investigate the spin structure of the
pressure-induced magnetic ordering in the spin gap system TlCuCl. Below the
ordering temperature K for the hydrostatic pressure
GPa, magnetic Bragg reflections were observed at the reciprocal lattice points
{\mib Q}=(h, 0, l) with integer and odd , which are equivalent to
those points with the lowest magnetic excitation energy at ambient pressure.
This indicates that the spin gap closes due to the applied pressure. The spin
structure of the pressure-induced magnetic ordered state for GPa was
determined.Comment: 4 pages, 3 figures, 3 eps files, jpsj2.cls styl
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