34,257 research outputs found
Magnetic properties of a disordered Heisenberg binary spin system with long-range exchange
The influence of substitutional disorder on the magnetic properties of
disordered Heisenberg binary spin systems with long-range exchange integrals is
studied. The equation of motion for the magnon Green's function which is
decoupled by the Tyablikov approximation is solved in the
Blackman-Esterling-Berk(BEB) coherent potential approximation(CPA) framework,
where the environmental disorder term is treated by virtual crystal
approximation. The long-range exchange integrals include a power-law decaying
and an oscillating Ruderman-Kittel-Kasuya-Yosida(RKKY) exchange interaction.
The resulting spectral density, which is calculated by CPA self-consistent
equation, is then used to estimate the magnetization and Curie temperature. The
results show, in the case of the three-dimensional simple cubic systems, a
strong influence of ferromagnetic long-range exchange integrals on the
magnetization and Curie temperature of the systems, which is obviously
different from the calculation of short-range interaction.Comment: 5 pages, 3 figures, to be accepted by PR
Data Unfolding with Wiener-SVD Method
Data unfolding is a common analysis technique used in HEP data analysis.
Inspired by the deconvolution technique in the digital signal processing, a new
unfolding technique based on the SVD technique and the well-known Wiener filter
is introduced. The Wiener-SVD unfolding approach achieves the unfolding by
maximizing the signal to noise ratios in the effective frequency domain given
expectations of signal and noise and is free from regularization parameter.
Through a couple examples, the pros and cons of the Wiener-SVD approach as well
as the nature of the unfolded results are discussed.Comment: 26 pages, 12 figures, match the accepted version by JINS
Generalized linear isotherm regularity equation of state applied to metals
A three-parameter equation of state (EOS) without physically incorrect
oscillations is proposed based on the generalized Lennard-Jones (GLJ) potential
and the approach in developing linear isotherm regularity (LIR) EOS of Parsafar
and Mason [J. Phys. Chem., 1994, 49, 3049]. The proposed (GLIR) EOS can include
the LIR EOS therein as a special case. The three-parameter GLIR, Parsafar and
Mason (PM) [Phys. Rev. B, 1994, 49, 3049], Shanker, Singh and Kushwah (SSK)
[Physica B, 1997, 229, 419], Parsafar, Spohr and Patey (PSP) [J. Phys. Chem. B,
2009, 113, 11980], and reformulated PM and SSK EOSs are applied to 30 metallic
solids within wide pressure ranges. It is shown that the PM, PMR and PSP EOSs
for most solids, and the SSK and SSKR EOSs for several solids, have physically
incorrect turning points, and pressure becomes negative at high enough
pressure. The GLIR EOS is capable not only of overcoming the problem existing
in other five EOSs where the pressure becomes negative at high pressure, but
also gives results superior to other EOSs.Comment: 9 pages, 3 figure
Two-dimensional electron-gas actuation and transduction for GaAs nanoelectromechanical systems
We have fabricated doubly clamped beams from GaAs/AlGaAs quantum-well heterostructures containing a high-mobility two-dimensional electron gas (2DEG). Applying an rf drive to in-plane side gates excites the beam's mechanical resonance through a dipole–dipole mechanism. Sensitive high-frequency displacement transduction is achieved by measuring the ac emf developed across the 2DEG in the presence of a constant dc sense current. The high mobility of the incorporated 2DEG provides low-noise, low-power, and high-gain electromechanical displacement sensing through combined piezoelectric and piezoresistive mechanisms
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