59 research outputs found
Modulation of Noise in Submicron GaAs/AlGaAs Hall Devices by Gating
We present a systematic characterization of fluctuations in submicron Hall
devices based on GaAs/AlGaAs two-dimensional electron gas heterostructures at
temperatures between 1.5 K to 60 K. A large variety of noise spectra, from 1/f
to Lorentzian, are obtained by gating the Hall devices. The noise level can be
reduced by up to several orders of magnitude with a moderate gate voltage of
0.2 V, whereas the carrier density increases less than 60% in the same range.
The significant dependence of the Hall noise spectra on temperature and gate
voltage is explained in terms of the switching processes related to impurities
in n-AlGaAs.Comment: 5 pages, 4 fig
A spin Esaki diode
We demonstrate electrical electron spin injection via interband tunneling in
ferromagnetic/nonmagnetic semiconductor Esaki diodes. An interband tunnel
junction between ferromagnetic p+-(Ga,Mn)As and nonmagnetic n+-GaAs under
reverse-bias allows spin-polarized tunneling of electrons from the valence band
of (Ga,Mn)As to the conduction band of n+-GaAs. The spin polarization of
tunneled electrons is probed by circular polarization of electroluminescence
(EL) from an n-GaAs/InGaAs/p-GaAs light emitting structure integrated with the
diode. Clear hysteresis loop with +-6.5% remanence is observed in the
magnetic-field dependence of the EL polarization at 6 K, below the Curie
temperature of (Ga,Mn)As.Comment: 11pages, 4figures. Submitted Japanese Journal of Applied Physics Pt2
Express Lette
Magnetization Reversal in Elongated Fe Nanoparticles
Magnetization reversal of individual, isolated high-aspect-ratio Fe
nanoparticles with diameters comparable to the magnetic exchange length is
studied by high-sensitivity submicron Hall magnetometry. For a Fe nanoparticle
with diameter of 5 nm, the magnetization reversal is found to be an incoherent
process with localized nucleation assisted by thermal activation, even though
the particle has a single-domain static state. For a larger elongated Fe
nanoparticle with a diameter greater than 10 nm, the inhomogeneous magnetic
structure of the particle plays important role in the reversal process.Comment: 6 pages, 6 figures, to appear in Phys. Rev. B (2005
Studies on Synthetic Pyrethroid. (XI) : Another Evidence for the trans-Configuration of a,o-Dimethylsorbic Acid
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