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排序方式: 共有296条查询结果,搜索用时 15 毫秒
101.
Ji Oon Lee 《Journal of statistical physics》2009,134(1):1-18
It is well known that the ground state energy of a three dimensional dilute Bose gas in the thermodynamic limit is E=4π
a
ρ
N when the particles interact via a non-negative, finite range, spherically symmetric, two-body potential. Here, N is the number of particles, ρ is the density of the gas, and a is the scattering length of the potential. In this paper, we prove the same result without the non-negativity condition on
the potential, provided the negative part is small. 相似文献
102.
Epitaxial films of ZnO doped with magnetic ion Fe and, in some cases, with 1% Al show clear evidence of room temperature ferromagnetic ordering but containing huge amount of paramagnetic moment in it. The total ferromagnetic and paramagnetic contributions have been extracted from the low temperature SQUID measurements. A clear correlation between the magnetization per transition metal ion and the ratio of the number of carriers and number of donors have been found in these films and established the theory of carrier induced ferromagnetism. The experimental data has been best explained through the modification of electronic structure of oxide semiconductors with impurity states. 相似文献
103.
M. Shakil Abrar Hussain M. Zafar Shabir Ahmad M.I. Khan M. Kashif Masood Abdul Majid 《Chinese Journal of Physics (Taipei)》2018,56(4):1570-1577
Gallium nitride is a wide band gap semiconductor material that has drawn significant interest due to its potential applications in opto-electronics and spin-tronics devices that can be operated above room temperature. First principle calculations by density functional theory have a key role in the field of materials science research. Theoretical findings on gallium nitride revealed that it shows ferromagnetic behavior doped by transition metals (i.e. 3d and 4d metals) and rare-earth elements. Ferromagnetism developed in gallium nitride by doping 3d (Ti, Cr, Mn, Fe, Co, Ni, and Cu), 4d metals (Ag and Pd), and rare-earth elements (Eu, Gd, and Ce) is discussed in this review. Effect of concentration on magnetic moment is also discussed. The origin of magnetism and exchange interaction that play a vital role in ferromagnetic and anti-ferromagnetic behavior is also explained. P-d exchange mechanism, s-d hybridization, and exchange mechanism are also explained in detail. 相似文献
104.
《Current Applied Physics》2018,18(1):68-78
In this study, molecular characteristics of polystyrene (PS) was calculated measuring its dilute-solution properties in toluene at 288.15 K via molecular dynamics (MD) simulations. The solution models consisted of PS chains with different number of repeating units all of which were in a dilute regime. In order to investigate the compatibility between the polymer and the solvent molecules, interaction energy and Flory-Huggins (FH) interaction parameter were estimated. The simulation results indicate that increasing the chain repeating units enhanced the interaction between the solute and the solvent. Additionally, the chain dimensions were evaluated calculating the radius of gyration (Rg) and end-to-end distance, r0. To determine the dynamic behavior of the chains in the solutions, mean square displacement (MSD) and diffusivity coefficient were calculated. The simulation results indicated that the chain rigidity at low molecular weight and chain flexibility with increasing the molecular weight influenced chains dynamic behavior and diffusivity. Moreover, radial distribution function (RDF) illustrated the effect of steric hindrance of the chains in dilute solution on capturing the solvent molecules. In addition, solution viscosity was calculated by performing non-equilibrium molecular dynamics simulation (NEMD). The obtained results of chain characteristics and viscosity showed a good agreement with experimental results published previously. This agreement confirms the accuracy of the applied simulation method to characterize the dilute solutions and the chains characteristics. 相似文献
105.
The influence of the Dresselhaus spin--orbit coupling on the tunnelling magnetoresistance in ferromagnet/ insulator /semiconductor/ insulator /ferromagnet tunnel junctions 下载免费PDF全文
This paper investigates the effect of Dresselhaus spin--orbit
coupling on the spin-transport properties of
ferromagnet/insulator/semiconductor/insulator/ferromagnet
double-barrier structures. The influence of the thickness of the
insulator between the ferromagnet and the semiconductor on the
polarization is also considered. The obtained results indicate that
(i) the polarization can be enhanced by reducing the insulator
layers at zero temperature, and (ii) the tunnelling magnetoresistance
inversion can be illustrated by the influence of the Dresselhaus
spin--orbit coupling effect in the double-barrier structure. Due to
the Dresselhaus spin--orbit coupling effect, the tunnelling
magnetoresistance inversion occurs when the energy of a localized
state in the barrier matches the Fermi energy EF of the
ferromagnetic electrodes. 相似文献
106.
Y. Sun A. Erol M. Yilmaz M. C. Arikan B. Ulug A. Ulug N. Balkan M. Sopanen O. Reentilä M. Mattila C. Fontaine A. Arnoult 《Optical and Quantum Electronics》2008,40(7):467-474
We present a comprehensive study of spectral photoluminescence (PL), photoconductivity and Hall mobility in undoped, n and
p-type modulation-doped quantum wells of Ga1-x
In
x
N
y
As1-y
/GaAs with varying nitrogen concentration. We show that the increasing nitrogen composition red shifts the energy gap and
this red shift is accompanied with a reduction of the 2D electron mobility in the quantum wells. True temperature dependence
of the band gap, free from errors associated with nitrogen induced exciton trapping effects, is observed because in the modulation
doped QW samples PL emission is dominated by band-to-band recombination and the S-shape temperature dependence is eliminated.
Excellent fit to semi-experimental Varshni equation is obtained and the temperature dependence of the band gap in the linear
regime (dE/dT) is tabulated as a function of nitrogen concentration and the type of dopant. 相似文献
107.
Chandana Rath Sonal Singh P. Mallick D. Pandey N. P. Lalla N. C. Mishra 《Indian Journal of Physics》2009,83(4):415-421
Ferromagentic semiconductors have been actively pursued because of their potential as spin polarized carrier sources and easy
integration into semiconductor technology. One such material, ZnO has been shown to be a potential Diluted Magnetic Semiconductor
(DMS). The appearance of ferromagnetism, however, is found to be sensitive to the processing conditions. We report synthesis
of ZnO nanoparticles of size ∼20 nm by a simple co-precipitation technique using metal nitrates and NaOH as precipitant. The
particles are self-organised and reveal single crystalline behaviour in electron diffraction pattern. Incorporation of Co
in ZnO matrix leads not only to the reduction in crystallite size but also to the modification of the structure. At 5% Co,
the particles are highly textured. The particles also aggregate and the aggregated mass have nearly rectangular shape as seen
through TEM. Increasing Co to 10%, results into further reduction of particle size and the particles self organize in a line,
which looks like nanofibers. This alignment of particles increases by increasing the Co content further. This type of growth
of nanofibers above Co ≥ 10% is well correlated with the anisotropic peak broadening observed in the XRD spectra. In addition,
Co substitute Zn site up to 20% without showing any extra phase in XRD spectra as compared to 7 to 10% in case of bulk. Transport
and magnetic studies indicate that conductivity increases with increasing Co content, but carrier mediated ferromagnetism
is absent down to 10 K.
相似文献
108.
109.
A gap in the spectrum of spin and ferroelectric waves is investigated versus magnetic and electric fields. It is demonstrated
that the magnetoelectric interaction is amplified with increasing external magnetic field and is weakened with increasing
external electric field. This allows the interaction between the spin and ferroelectric subsystems to be controlled by external
fields.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 43–47, February, 2009. 相似文献
110.
The homogenization results obtained by Bacca et al. (2013a), to identify the effective second-gradient elastic materials from heterogeneous Cauchy elastic solids, are extended here to the case of phases having non-isotropic tensors of inertia. It is shown that the nonlocal constitutive tensor for the homogenized material depends on both the inertia properties of the RVE and the difference between the effective and the matrix local elastic tensors. Results show that: (i) orthotropic nonlocal effects follow from homogenization of a dilute distribution of aligned elliptical holes and, in the limit case, of cracks; (ii) even under the dilute assumption and isotropic local effective behaviour, homogenization may lead to effective nonlocal orthotropic properties. 相似文献