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1.
M. N. Khlopkin 《JETP Letters》1999,69(1):26-30
The specific heat of a V3Si single crystal (T
c=17 K, H
c2=20 T) in magnetic fields up to 8 T isinvestigated experimentally for three orientations of the field relative to the crystallographic
directions — H∥〈001〉, H∥〈110〉, and H∥〈111〉. Both the upper critical magnetic field and the specific heat of the mixed state are observed to depend on the orientation
of the magnetic field relative to the crystallographic directions (anisotropy): The critical field reaches its maximum value
and the specific heat its minimum value in a field along the 〈001〉 direction. The anisotropy scale in both phenomena increases
as the magnetic field and reaches 3% in a 6 T field. The interrelationship of the upper critical field anisotropy and the
specific-heat anisotropy in type-II superconductors is studied. It is shown that the anisotropy of the specific heat in the
mixed state in weak fields can serve as a criterion for nontrivial pairing.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 1, 26–29 (10 January 1999) 相似文献
2.
The possibility of resonance during elastic intravalley scattering in n-type semiconductors is investigated in connection with the crossing (due to anisotropy of the effective mass) of the energy
levels of excited states of a shallow donor as functions of the magnetic field. The hybridization of states of different frequencies
in the vicinity of a crossing is attributed to the emergence of a nonzero dipole moment of the excited impurity atom and,
accordingly, a long-range potential, which creates carrier-transport anomalies. The lower part of the donor spectrum is calculated
as a function of the magnetic field in Si with B∥〈001〉 and in Ge with B∥〈111〉 or B∥〈110〉. A crossing occurs in Ge in the field range 9.9 T<B<16.7 T and in Si in the field range 10.5 T<B<37.7 T. The characteristic longitudinal relaxation time and the transverse conductivity, which are determined by scattering
at excited donors in the presence of the hybridization of states, are calculated.
Zh. éksp. Teor. Fiz. 112, 975–1010 (September 1997) 相似文献
3.
M.?B.?Krasil’nikov O.?I.?Rozhdestvenski? A.?G.?Smolin O.?S.?Vasyutinski? 《Optics and Spectroscopy》2010,109(4):486-492
A general expression is obtained for the Raman scattering intensity in an ensemble of diatomic molecules for an arbitrary
geometry of the experiment as a function of the anisotropy of angular distribution of molecular axes. In its derivation, the
irreducible representation of the density matrix of molecules was used. It is shown that, in the Raman scattering experiments
on the study of the anisotropy of molecular ensembles, a significant contribution to the signal is made, not only by the second-order
terms 〈cos2θ〉, but also by the fourth-order terms proportional to 〈cos4θ〉, which should be taken into account to correctly interpret the experimental data. Convenient experimental geometries are
proposed that allow the anisotropy of a molecular ensemble to be investigated. 相似文献
4.
D. M. Sedrakyan D. A. Badalyan V. M. Gasparyan A. Zh. Khachatryan 《Journal of Experimental and Theoretical Physics》1997,84(2):317-321
We find the dependence of the ensemble-averaged resistance, 〈ρ
L〉, of a one-dimensional chain consisting of periodically spaced random delta-function potentials of the chain length L, the incident-electron energy, and the chain disorder parameter w. We show that generally the 〈ρ
L〉 vs L dependence can be written as a sum of three exponential functions, two of which tend to zero as L℩∞. Hence the asymptotic expression for 〈ρ
L〉 is always an exponential function of L. Such an expression for 〈ρ
L〉 means that the electronic states are indeed localized and makes it possible (which is important) to find the dependence
of the localization radius on the incident-electron energy and the force with which an electron interacts with the sites of
the chain. We also derive a recurrence representation for 〈ρ
L〉, which proves convenient in numerical calculations.
Zh. éksp. Teor. Fiz. 111, 575–584 (February 1997) 相似文献
5.
Wenwei Ge Hong Liu Xiangyong Zhao Xiaobing Li Xiaoming Pan Di Lin Haiqing Xu Xiangping Jiang Haosu Luo 《Applied Physics A: Materials Science & Processing》2009,95(3):761-767
In this paper, a single crystal of 0.96Na0.5Bi0.5TiO3-0.04BaTiO3 with dimensions of Φ 30×10 mm was grown by the top-seeded-solution growth method. X-ray powder diffraction results show that the as-grown crystal
possesses the rhombohedral perovskite-type structure. The dielectric, piezoelectric and electrical conductivity properties
were systematically investigated with 〈001〉, 〈110〉 and 〈111〉 oriented crystal samples. The room-temperature dielectric constants
for the 〈001〉, 〈110〉 and 〈111〉 oriented crystal samples are found to be 650, 740 and 400 at 1 kHz. The (T
m, ε
m) values of the dielectric temperature spectra are almost independent of the crystal orientations; they are (306°C, 3718),
(305°C, 3613) and (307°C, 3600) at 1 kHz for the 〈001〉, 〈110〉 and 〈111〉 oriented crystal. The optimum poling conditions were
obtained by investigating the piezoelectric constants d
33 as a function of poling temperature and poling electric field. For the 〈001〉 and 〈110〉 crystal samples, the maximum d
33 values of 146 and 117 pC/N are obtained when a poling electric field of 3.5 kV/mm and a poling temperature of 80°C were applied
during the poling process. The as-grown 0.96Na0.5Bi0.5TiO3-0.04BaTiO3 crystal possesses a relatively large dc electrical conductivity, especially at higher temperature, having a value of 1.98×10−11 Ω−1⋅m−1 and 3.95×10−9 Ω−1⋅m−1 at 25°C and 150°C for the 〈001〉 oriented crystal sample. 相似文献
6.
The orientational dependence for different groups of secondary electrons — quasi-elastically scattered, inelastically reflected
with excitation of a plasmon and with ionization of the core level M
4.5, and the Auger electrons M
4.5
VV — are measured in the primary electron energy range 0.6–1.5 keV. The data are obtained for a Nb (100) single crystal by varying
the azimuthal angle of incidence of the primary beam, with complete collection of secondaries. A relationship is established
between the processes of focusing and defocusing of the electrons that have penetrated into the crystal in the 〈110〉 and 〈133〉
directions, which differ substantially in the atomic packing density. Specific details of the Auger orientation effect, due
to the focusinginduced variation of the flux density of the reflected electrons, are identified and explained. The contributions,
both of anisotropy of ionization of the core level and of variation of the backscattering intensity, to the angular dependence
of Auger emission and reflection with ionization loss are estimated. The possibilities of using such orientational dependences
for an element-sensitive analysis of the local atomic structure of surfaces are assessed.
Zh. Tekh. Fiz. 67, 117–123 (August 1997) 相似文献
7.
The statistics of energy levels for a disordered conductor are considered in the critical energy window near the mobility
edge. It is shown that, if the critical wave functions are multifractal, the one-dimensional gas of levels on the energy axis
is compressible, in the sense that the variance of the level number in an interval is 〈 (δN)2〉∼χ〈N〉 for 〈N〉≫1. The compressibility, χ=η/2d, is given exactly in terms of the multifractal exponent η =d−D
2 at the mobility edge in a d-dimensional system.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 5, 355–360 (10 September 1996)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
8.
J. K. Baria 《Czechoslovak Journal of Physics》2004,54(4):469-485
A model pseudopotential depending on an effective core radius but otherwise parameter free is used to study the interatomic
interactions, phonon dispersion curves (inq and r-space analysis), phonon density of states, mode Grüneisen parameters, dynamical elastic constants (C
11,C
12 andC
44), bulk modulus (B), shear modulus (C′), deviation from Cauchy relation (C
12–C
44), Poisson’s ratio (σ), Young’s modulus (Y), behavior of phonon frequencies in the elastic limit independent of the direction (Y
1), limiting value in the [110] direction (Y
2), degree of elastic anisotropy (A), maximum frequencyω
max, mean frequency 〈ω〉, 〈ω
2〉1/2=(〈ω〉/〈ω
−1〉)1/2, fundamental frequency 〈ω
2〉, and propagation velocities of the elastic constants in Cu, Ag, Au, Ni, Pd, and Pt. The contribution of s-like electrons
is calculated in the second-order perturbation theory for the model potential while that of d-like electrons is taken into
account by introducing repulsive short-range Born-Mayer like term. Very recently proposed screening function due to Sarkar
et al. has been used to obtain the screened form factor. The theoretical results are compared with experimental findings wherever
possible. A good agreement between theoretical investigations and experimental findings has proved the ability of our model
potential for predicting a large number of physical properties of transition metals. 相似文献
9.
The redistribution of the electronic polarization in deuterium atoms is analyzed theoretically and the various polarization
moments are shown to influence the magnetic resonance signal of deuterium. The analysis gives expressions that relate the
amplitudes of the magnetic resonance signals for various Zeemann sublevels of the D atom to the electronic and nuclear polarizations
of these atoms and their nuclear alignment. Experimental data on the optical orientation and spin exchange in a D-Cs mixture
are used to determine the electronic and nuclear orientation and nuclear alignment of the D atoms, which are found to be 〈S
z〉=0.1, 〈I
z〉=0.27, and 〈Q
zz=0.027.
Zh. Tekh. Fiz. 67, 22–26 (January 1997) 相似文献
10.
D. E. Feldman 《JETP Letters》1999,70(2):135-140
The random field and random anisotropy N-vector models are studied with the functional renormalization group in 4−ε dimensions. The random anisotropy Heisenberg (N=3) model has a phase with an infinite correlation length at low temperatures and weak disorder. The correlation function
of the magnetization obeys a power law 〈m(r
1)m(r
2)〉∼|r
1−r
2|− 0.62ε. The magnetic susceptibility diverges at low fields as χ∼H
−1+0.15ε. In the random field N-vector model the correlation length is finite at arbitrarily weak disorder for any N>3.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 2, 130–135 (25 July 1999)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
11.
EPR spectra of deep boron in 4H-SiC and 3C-SiC crystals have been observed and studied. Two sites in 4H-SiC produced deep-boron EPR signals, quasi-cubic k and hexagonal h. In both cases the deep-boron center symmetry is close to axial along the c crystal axis, and the g factor anisotropy is about an order of magnitude larger than that for shallow boron centers. In the 3C-SiC crystal, the deep-boron symmetry is also close to axial along one of the four 〈111〉 directions. The model proposed for
the deep boron center with acceptor properties is BSi-v
C, where BSi is the boron substituting for silicon, and v
C is the carbon vacancy, with the BSi-v
C direction coinciding in 4HSiC with the hexagonal axis of the crystal for both k and h positions. In the cubic 3C-SiC crystal, there are four equivalent deep boron centers, which represent BSi-v
C pairs with the bond directed along one of the four 〈111〉 crystal directions.
Fiz. Tverd. Tela (St. Petersburg) 40, 36–40 (January 1998) 相似文献
12.
A system of equations is derived for moments [averages of spherical harmonics 〈Y
l,m
〉(t)] that determine the dynamics of the magnetization M of a superparamagnetic particle in a fluctuating field. The system is derived by representing the Gilbert equation in a fluctuating
field, and the corresponding Fokker-Planck equation for the distribution function of M, in terms of angular momentum operators, which in turn makes it possible to express the coefficients of the system of moment
equations in terms of Clebsch-Gordan coefficients.
Fiz. Tverd. Tela (St. Petersburg) 41, 2020–2027 (November 1999) 相似文献
13.
N. A. Silant’ev 《Journal of Experimental and Theoretical Physics》1999,89(1):45-55
In this paper the procedure of large-scale averaging of the magnetic-field diffusion equation with the α-term curlα(r,t)B(r,t) is used to show that a nonuniform distribution of the turbulent helicity fluctuations (more precisely, the fluctuations
of the coefficient α) with a zero average value gives rise to large-scale amplification of the initial magnetic field. A detailed study is carried
out of the dependence of the resulting large-scale α effect on the characteristics of the correlator 〈〈α(r, t)α(r″,t″)〉〉 in a rotating medium with a nonuniform distribution of the angular velocity ω=ω(ρ,z) (ρ is the distance for the rotation axis z). The effect of helicity fluctuations and the diffusion coefficient on the turbulent diffusion process is also investigated.
Zh. éksp. Teor. Fiz. 116, 85–104 (July 1999) 相似文献
14.
The NMR of 55Mn in the quasi-one-dimensional noncollinear antiferromagnet CsMnI3 at T=1.3 K is investigated in magnetic fields up to ∼40 kOe. Six NMR branches corresponding to six manganese spins per magnetic
unit cell are observed. The NMR spectra correspond satisfactorily to the well-known magnetic structure of CsMnI3, taking into account the dynamic frequency shift due to the interaction with the low-lying AFMR modes. The average spins
〈S
A〉=1.86 and 〈S
B〉=1.74 of the magnetically nonequivalent Mn2+ ions are determined from the measured values of the hyperfine fields. The results obtained agree qualitatively with the calculations
of spin reduction in quasi-one-dimensional antiferromagnets [Y. Watabe, T. Suzuki, and Y. Natsume, Phys. Rev. B 52, 3400 (1995)].
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 9, 661–665 (10 May 1998) 相似文献
15.
B. Ya. Balagurov 《Journal of Experimental and Theoretical Physics》2011,112(2):327-332
The conductivity of a weakly inhomogeneous anisotropic medium is considered. The effective conductivity tensor $
\hat \sigma _e
$
\hat \sigma _e
is determined in the approximation quadratic in deviation of local conductivity $
\hat \sigma
$
\hat \sigma
(r) from mean value 〈$
\hat \sigma
$
\hat \sigma
〉 for an arbitrary anisotropy of the composite. 相似文献
16.
R. T. Sibatov 《JETP Letters》2011,93(9):503-507
Distributions of the conductance G of a long quantum wire with the fractal distribution of barriers have been obtained in the successive incoherent tunneling
regime. The asymptotic behavior (in the limit L → ∞) of moments 〈G
k
(L)〉, average power of the shot noise 〈S(L)〉, and Fano factor agree with the results of the work [C. W. J. Beenakker et al., Phys. Rev. B 79, 024204 (2009)], and the distributions themselves describe well the Monte Carlo simulation results. The equation that has
been obtained for the distributions of the resistance and conductance agrees with the recent fractional differential generalization
of the Dorokhov-Mello-Pereyra-Kumar equation for the quasi-one-dimensional multichannel disordered semiconductors with a self-similar
distribution of scatterers. 相似文献
17.
The mean area of a two-dimensional Gaussian ring of N monomers is known to diverge when the ring is subject to a critical pressure differential, p
c ∼ N
-1. In a recent publication (Eur. Phys. J. E 19, 461 (2006)) we have shown that for an inextensible freely jointed ring this divergence turns into a second-order transition
from a crumpled state, where the mean area scales as 〈A〉 ∼ N, to a smooth state with 〈A〉 ∼ N
2. In the current work we extend these two models to the case where the swelling of the ring is caused by trapped ideal-gas
particles. The Gaussian model is solved exactly, and the freely jointed one is treated using a Flory argument, mean-field
theory, and Monte Carlo simulations. For a fixed number Q of trapped particles the criticality disappears in both models through an unusual mechanism, arising from the absence of
an area constraint. In the Gaussian case the ring swells to such a mean area, 〈A〉 ∼ NQ, that the pressure exerted by the particles is at p
c for any Q. In the freely jointed model the mean area is such that the particle pressure is always higher than p
c, and 〈A〉 consequently follows a single scaling law, 〈A〉 ∼ N
2
f (Q/N), for any Q. By contrast, when the particles are in contact with a reservoir of fixed chemical potential, the criticality is retained.
Thus, the two ensembles are manifestly inequivalent in these systems.
An erratum to this article is available at . 相似文献
18.
Summary The dislocation relaxation maximum has been investigated at frequencies of 5, 10 and 30 MHz. The three (very high-purity)
silver crystals of crystallographic orientation 〈111〉, 〈110〉 and 〈100〉 which are given a resolved shear stress of 20 MPa were
found to produce dislocation relaxation maximum at 107 K in all the three samples. The maximum shifts to 117 K when measurement
is carried out at 10 MHz and to 127 K at 30 MHz. The results reveal that the maximum is orientation independent. The activation
energy and the attempt frequency were calculated and found to be equal to 0.105 eV and 2·109 Hz, respectively. Meanwhile the larger magnitude of the maximum was found on the 〈111〉 crystal and the least was on the 〈100〉
crystal. Finally, it was clearly shown that the dislocation relaxation strength decreases as the frequency increases. 相似文献
19.
The appearance of a current in an external circuit has been observed upon elastic deformation of a local region of the superionic
crystal RbAg4I5. The dependence of the magnitude and sign of the deformation current on the region of application of the local load on the
sample is examined, and the temporal characteristics of the processes are investigated. The influence of an elastic deformation
on processes taking place at the 〈superionic crystal〉-〈electrode〉 heterojunction is investigated, and a mechanism of generation
of the deformation current is proposed. The generation of photostimulated currents upon illumination of a local region of
the superionic conductor by light corresponding to intracenter excitation of optically active centers is considered. It is
shown that the elastic stress fields arising around photoexcited centers are responsible for the generation of photostimulated
currents.
Fiz. Tverd. Tela (St. Petersburg) 41, 1766–1771 (October 1999) 相似文献
20.
Summary The turbulent hydrodynamic diffusion may essentially change the kinetics of the elementary chemical reactions. The much faster
character of the turbulent diffusion and the evolution of the relative displacements of particles in the inertial range according
to the Richardson law, 〈Δr
2〉 ∞t
3, rather than 〈Δr
2〉 ∞t, remove in many cases the ?bottleneck? effects created by the molecular diffusion and seriously influences the diffusioncontrolled
processes. It changes also the Debye screening of the charged particles in the turbulent fluids and the scenario of the Turing
instability. These problems are discussed in our paper. The consideration is based and on the Obukhov's suggestion on the
Markovian character of evolution of liquid particles in turbulent flows. The role of non-Markovian corrections is also briefly
discussed.
To speed up pubblication, the authors of this paper have agreed to not receive the proofs for correction. 相似文献