共查询到20条相似文献,搜索用时 15 毫秒
1.
M. V. Koval’chuk A. Ya. Kreines Yu. A. Osip’yan V. V. Kvardakov V. A. Somenkov 《JETP Letters》1997,65(9):734-737
Curves of the secondary-fluorescence yield from the constituent elements of high-T
c
superconducting crystals Nd1.85Ce0.15CuO4−δ are measured in the dynamic x-ray diffraction regime. The form of the curves attests to the appearance of a standing x-ray
wave in the crystal.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 9, 703–706 (10 May 1997) 相似文献
2.
Kh. K. Aliev I. K. Kamilov Kh. I. Magomedgadzhiev M. -G. K. Omarov 《Physics of the Solid State》1997,39(2):296-297
The absorption coefficient α
k for longitudinal ultrasonic (15 MHz) waves propagating transverse to the direction of a magnetic field H is measured in single crystal gadolinium. It is found that in fields H⩽600 Oe, the peak in α
k is shifted toward lower temperatures, while the absolute magnitude of the absorption rises with increasing H. It is shown on the basis of dynamic scaling that the anomalous behavior of α
k in fields H⩽600 Oe can be explained by introducing a magnetic field analog of the Landau-Khalatnikov relaxation mechanism.
Fiz. Tverd. Tela (St. Petersburg) 39, 339–340 (February 1997) 相似文献
3.
S. N. Popov 《Physics of the Solid State》1999,41(7):1175-1181
The temperature dependences of NQR line frequencies and widths of 121Sb (for the ±1/2→±3/2 transition) and of 123Sb (for the ±1/2→±3/2 and ±3/2→±5/2 transitions), as well as of the principal components and the asymmetry parameter of the
electric-field-gradient tensor at the 123Sb nucleus have been studied in a SbSI crystal in the 115–325 K range. The dynamic and static factors governing the character
of these relations are discussed. The ±1/2→±3/2 line in the 121Sb NQR spectrum splits into a doublet within a narrow (0.5 K) temperature interval near the ferroelectric phase transition
(T
c=293 K), which is associated with the formation of a macroscopic heterophase structure in the crystal.
Fiz. Tverd. Tela (St. Petersburg) 41, 1286–1292 (July 1999) 相似文献
4.
O. V. Ivanov D. A. Shport E. G. Maksimov 《Journal of Experimental and Theoretical Physics》1998,87(1):186-199
First-principles calculations are performed relating to the stability of a series of perovskite crystals with respect to transition
to the ferroelectric and the antiferroelectric state. The calculations employ the generalized Gordon-Kim method, in which
the total charge density of an ionic crystal is represented as a superposition of the densities of the individual ions. In
the spirit of the nonequilibrium thermodynamics of Leontovich the charge density of an individual ion is calculated in the
presence of external auxiliary fields which deform this density. Multipole deformations up to quadrupole are taken into account.
The actual magnitude of the deformation is found by minimizing the total energy of the crystal in the Thomas-Fermi-Dirac approximation.
The calculated values of the ion shifts in the ferroelectric phase for BaTiO3, and also the electron contribution to the dielectric constant ε
∞ and the dynamic Born effective charges Z
eff are found to be in good agreement with the experimental data. The proposed method allows one to obtain an analytical expression
for ε
∞, Z
eff, and the dynamic vibration matrix. It is shown that these expressions formally coincide with the expressions arising in the
phenomenological models of the polarized and deformed ion. Analysis of the expressions obtained confirms the validity of the
classical theory of ferroelectrics of displacement type for perovskite crystals.
Zh. éksp. Teor. Fiz. 114, 333–358 (July 1998) 相似文献
5.
A numerical measure of the difference between crystal lattices is determined. The fruitfulness of the definition is demonstrated
for a specific example concerning the prominence of an orientational correspondence between the body-centered crystal lattice
[bcc(bct)] of α-martensite and the face-centered crystal lattice (fcc) of γ-austenite in cases where the latter is perfect and where it differs from a perfect lattice near a screw dislocation.
Zh. Tekh. Fiz. 69, 60–64 (May 1999) 相似文献
6.
The acoustoelectromagnetic interaction is examined in a regime where three mechanisms must be taken into account simultaneously:
photoelasticity, quadratic photoelasticity, and elastic nonlinearity. It is shown that beyond the critical conditions, acoustic
solitary waves are formed at harmonic and subharmonic frequencies in a crystal. Including damping and nonideal reflection
at the boundaries does not lead to the establishment of any sort of stationary state: a soliton spatial-temporal dynamic develops.
Fiz. Tverd. Tela (St. Petersburg) 39, 1101–1104 (June 1997) 相似文献
7.
The photoconductivity in the range 0.3–0.9 eV was investigated in a high-quality C60 fullerene single crystal. It was concluded that the crystal investigated is an extrinsic semiconductor.
Fiz. Tverd. Tela (St. Petersburg) 41, 1113–1114 (June 1999) 相似文献
8.
K. N. Mikhalev S. V. Verkhovskii A. P. Gerashchenko Yu. V. Piskunov A. Yu. Yakubovskii A. P. Rusakov 《JETP Letters》1999,70(5):346-351
The spin-lattice relaxation times T
1 in Ba1−x
KxBiO3 (x=0.3, 0.4, 0.5) were measured in the normal temperature range (20–300 K).A substantial contribution to the spin-lattice relaxation
rate from dynamic local distortions of the crystal lattice near potassium atoms is found. The activation energy of this process
increases with decreasing potassium concentration, and the frequency of lattice excitations decreases. The nature of the low-frequency
lattice dynamics is discussed.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 5, 344–349 (10 September 1999) 相似文献
9.
E. A. Zubova L. I. Manevich N. K. Balabaev 《Journal of Experimental and Theoretical Physics》1999,88(3):586-589
A molecular-dynamics model of the behavior of a vacancy in the chain of an equilibrium polymer crystal (the “collective atom”
approximation for polyethylene) is developed for the first time. It is shown that a defect of this type in a polymer crystal
has a soliton mobility, as opposed to vacancies in crystals of low-molecular substances.
Zh. éksp. Teor. Fiz. 115, 1063–1069 (March 1999) 相似文献
10.
E. I. Kats 《JETP Letters》1997,65(9):725-728
The properties of a nematic liquid crystal in a porous matrix are discussed. On scales exceeding a certain characteristic
scale the liquid crystal behaves as a nematic glass. Application of a weak magnetic field restores long-range orientational
order.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 9, 695–698 (10 May 1997) 相似文献
11.
Q.D. Zeng C. Wang S.D. Xu C.L. Bai Y. Li X.J. Yan 《Applied Physics A: Materials Science & Processing》2001,73(2):247-250
Nanostructures are formed by photodimerization of crystalline 4,4′-dimethylbenzophenone (1) through intermolecular hydrogen abstraction and Baeyer–Villiger reaction of 1 with m-chloroperoxybenzoic acid (MCPBA) (5) in the solid state. Atomic force microscopy (AFM) reveals that the crystal face (001) of 1 during photodimerization exhibits volcanoes, whereas the same face (001) of 1 yields both craters and volcanoes all over
the surface from the contact edge of the crystals during the Baeyer–Villiger reaction. All the experimental results are correlated
with the bulk crystal structure. Molecular interpretation of the AFM features of 1 is given.
Received: 18 April 2000 / Revised version: 26 July 2000; accepted: 27 July 2000 / Published online: 30 November 2000 相似文献
12.
13.
S. N. Popov 《Physics of the Solid State》1997,39(7):1143-1146
A study has been made of the temperature dependences of the chlorine NQR frequency and linewidth in calomel crystals. These
dependences show clearly pronounced anomalies in the region of the ferroelastic phase transition. The dynamic and static factors
influencing the pattern of these dependences are discussed. A fine structure in the spin echo in the form of beats has been
revealed within a narrow temperature interval near the phase transition. This effect is shown to be connected with the formation
of a macroscopic heterophase superstructure in the crystal.
Fiz. Tverd. Tela (St. Petersburg) 39, 1287–1290 (July 1997) 相似文献
14.
An effect of nonpolarized white light on the modulated magnetic structure of a FeBO3:Mg single crystal, which arises in this light-plane weak ferromagnet in the low temperature range during technical magnetization,
has been revealed. It has been found that the degree of the light action on the magnetic state of FeBO3:Mg depends both on its duration and on the orientation of the spontaneous magnetization vector M of the crystal during illumination. Interpretation of the results obtained has been performed in the context of the “magnetic
ripple” theory on the assumption that the absorbed light induces additional uniaxial magnetic anisotropy in the easy plane
of the crystal and that the anisotropy axis is collinear to the vector M during illumination. 相似文献
15.
Summary For photon energies below the absorption edge in CdS, CdSe and other II–VI crystals the polariton dispersion curves forE⊥c andE‖c (c-axis in a wurtzite crystal) corss at some points called isotropic points (IP). The occurrence of isotropic points provides
the possibility of mode coupling between ordinary and extraordinary waves. Since the consequences of mode coupling on the
optical properties for photon energies near the lowest IP lying much below the first excitonic state were widely discussed
in recent years, more attention is now paid to isotropic points lying near the band gap and related to then=2,3, … excitonic states (?higher isotropic points?). Making use of Stahl's real density matrix approach we derive the polariton
dispersion relationsk
⊥ (ω), andk
‖ (ω), for CdS and CdSe bulk crystals and determine the positions of IP's due to the crossing of theB-polariton with higherA-excitonic resonances. By the method of multiple internal reflection we calculate the transmission spectra for various crystal
thicknesses (between 3 μm and 0.5 mm) and coupling mechanisms. The calculated transmission shows sharply peaked structures
centred at the isotropic points. 相似文献
16.
In agreement with a prediction of the theory, we have observed experimentally the intrinsic quadrupole electric field of a
centrosymmetric crystal.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 1, 15–20 (10 January 1998) 相似文献
17.
I. A. Ovid’ko 《Physics of the Solid State》1999,41(9):1500-1505
Theoretical concepts have been developed for a new type of misfit defects, misfit disclinations, at crystal/crystal and crystal/glass
interfaces. It is shown, in particular, that the formation of misfit disclinations is an efficient physical micromechanism
of misfit stress relaxation at crystal/crystal interfaces. A model describing misfit disclinations at crystal/glass interfaces
has been constructed. The energy characteristics of phase boundaries with misfit disclination ensembles are estimated.
Fiz. Tverd. Tela (St. Petersburg) 41, 1637–1643 (September 1999) 相似文献
18.
The temperature-amplitude region of existence of chaotic oscillations in a resonant circuit containing a triglycine sulfate
crystal shifts toward higher amplitudes of the repolarization field when the crystal is irradiated with small x-ray doses.
This trend is attributed to a change in the kinetics of the domain structure of the crystal in a strong electric field in
the presence of radiation defects.
Fiz. Tverd. Tela (St. Petersburg) 40, 716–718 (April 1998) 相似文献
19.
Calculations of the properties of NiO, CaO, SrO, and La2NiO4 crystals are used as a basis for determining empirical pairwise potentials which are employed in calculating the structure,
lattice dynamics, and certain properties of La2CuO4. The model developed here differs from those proposed before. First, the many-particle Jahn-Teller contributions to the energy
and dynamic matrix of the crystal are taken into account. Second, the analytic expressions for the pairwise potentials contain
an additional short-range electrostatic screening term. The results are in satisfactory agreement with experimental data.
Fiz. Tverd. Tela (St. Petersburg) 39, 1094–1100 (June 1997) 相似文献
20.
Xue-Hua Wang Ben-Yuan Gu 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(3):323-326
The analytic solution to the wave equation for small-signal sum-frequency process is derived in 2D χ
(2)
photonic crystals with use of the Green function method. It is predicted that the sum-frequency electrical field at quasi-phase
matching (QPM) resonance is proportional to the angle-dependent effective crystal length. This implies that multiple wavelength
QPM frequency conversion with controllable intensity output can be realized in a single 2D χ
(2)
photonic crystal. It is revealed that efficient frequency conversion requires both the QPM and the proper structure matching.
A novel double-circle construction, different from the conventional Ewald construction, is presented to reflect important
QPM processes. It is also shown that the QPM resonance tuning of second-harmonic generation can operate over the whole transparent
wavelength range of crystals.
Received 19 April 2001 相似文献