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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : ZOBOV V. E.
Заглавие : HIGH-FREQUENCY ASYMPTOTICS OF THE AUTOCORRELATION FUNCTION IN THE HEISENBERG PARAMAGNET
Место публикации : Phys. Lett. A: ELSEVIER SCIENCE BV, 1986. - Vol. 119, Is. 6. - P315-316. - ISSN 0375-9601, DOI 10.1016/0375-9601(86)90156-8
Примечания : Cited References: 8
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : ZOBOV V. E.
Заглавие : AUTOCORRELATION FUNCTIONS OF THE ANISOTROPIC HEISENBERG PARAMAGNET IN THE APPROXIMATION OF A SELF-CONSISTENT FLUCTUATING FIELD
Место публикации : Theor. Math. Phys.: PLENUM PUBL CORP, 1990. - Vol. 84, Is. 1. - P751-757. - ISSN 0040-5779, DOI 10.1007/BF01017200
Примечания : Cited References: 10
Предметные рубрики: RELAXATION
Аннотация: The method proposed earlier for investigating the dynamics of the isotropic Heisenberg paramagnet at high temperatures is generalized to the anisotropic case. A system of nonlinear integrodifferential equations relating the three autocorrelation functions of the x, y, and z components of an individual spin is obtained. A solution of the system is sought in the form of series in powers of the time and is investigated on the plane of the complex time variable. The coefficients of the series up to the tenth order for the xy model and the model with truncated dipole interaction are calculated, and the parameters of the singular points nearest the origin are determined from them.
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Popov M. A.
Заглавие : Excluded volume effects for frequency moments of the spin autocorrelation function of the Heisenberg model on a square lattice at high temperatures
Место публикации : J. Stat. Phys. - 1999. - Vol. 97, Is. 3-4. - P.793-802. - ISSN 0022-4715, DOI 10.1023/A:1004675527713
Примечания : Cited References: 17
Предметные рубрики:
Ключевые слова (''Своб.индексиров.''): spin dynamics--frequency moments--excluded volume--singular points
Аннотация: The expansion coefficients in powers of time (or frequency moments) of the spill autocorrelation Function are represented at the simple self-consistent approximation as a sum of weighted trees on a Bethe lattice. Using the computer numeration and the Monte Carlo method for self-avoidingly embedding these trees on the square lattice, we estimate the moments and the convergence radius of the expansion. We show that the moments decrease and the radius increases in consequence of the volume exclusion.
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Popov M. A.
Заглавие : The coordinate of a singular point of the time correlation functions for a heteronuclear spin system of a crystal
Место публикации : J. Exp. Theor. Phys.: AMER INST PHYSICS, 2005. - Vol. 100, Is. 4. - P775-783. - ISSN 1063-7761, DOI 10.1134/1.1926438
Примечания : Cited References: 24
Предметные рубрики: FLUCTUATION SPECTRUM
CROSS-RELAXATION
NMR ABSORPTION
SHAPE
WINGS
LINE
Ключевые слова (''Своб.индексиров.''): correlation methods--crystal lattices--crystallography--functions--integral equations--lithium compounds--nuclear magnetic resonance--quantum theory--random processes--autocorrelation functions (acf)--dipole-dipole interactions (ddi)--heteronuclear spin systems--self-consistent fluctuating field (scff)--crystals
Аннотация: The singularities of the time autocorrelation functions (ACFs) for a heteronuclear spin system of a crystal are investigated. Exact expressions are obtained for ten moments of the spectra of ACFs in the approximation of a self-consistent fluctuating field (SCFF) with arbitrary axial symmetry. These expressions are applied to determine the coordinate of the lowest singular point of these functions on the imaginary-time axis for a spin system with a dipole-dipole interaction (DDI). The leading corrections to this coordinate due to the correlation of local fields in real crystals are calculated. These corrections are determined by lattice sums with triangles of four bonds and pairs of four bonds. Numerical values of the coordinate are obtained for a LiF crystal in a magnetic field directed along three crystallographic axes. An increase in the coordinate of the singular point, which follows from the theory and leads to a faster falloff of the wings of the ACF spectra, qualitatively agrees with experiment. © 2005 Pleiades Publishing, Inc.
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrovsky A. S., Vyunishev A. M., Zaitsev A. I., Pospelov G. I., Slabko V. V.
Заглавие : Diagnostics of fs pulses by noncollinear random quasi-phase-matched frequency doubling
Место публикации : Appl. Phys. Lett. - 2011. - Vol. 99, Is. 21. - Ст.211105. - ISSN 0003-6951, DOI 10.1063/1.3664094
Примечания : Cited References: 12. - The work was supported by Ministry of Education and Science of Russian Federation (Contract No. 16.740.11.0150); Grant of President of Russian Federation for support of leading scientific schools Grant Nos. SS-4645.2010.2 and RNP.2.1.1.3455 and Projects Nos. 2.5.2 and 3.9.1 of PSB RAS and 27.1 and 5 of SB RAS. A. M. Vyunishev is grateful for the support from Krasnoyarsk Regional Fund of Science and Technical Activity Support.
Ключевые слова (''Своб.индексиров.''): autocorrelation measurement--cross-correlation measurements--fs pulse--noncollinear--nonlinear photonic crystals--nonuniformity--quasi-phase-matched frequency doubling--random structures--tetraborate--vacuum ultraviolets--wide spectral range--band structure--frequency doublers--strontium--photonic crystals
Аннотация: Noncollinear random quasi-phase-matched frequency doubling in nonlinear photonic crystal (NPC) of strontium tetraborate (SBO) can be used for background-free autocorrelation measurements of ultrashort pulses in wide spectral range without any angular tuning of nonlinear photonic crystal. Nonuniformity of reciprocal superlattice vectors spectrum of random structure does not affect the accuracy of measurement. Nonlinear photonic crystals of strontium tetraborate are attractive medium for cross-correlation measurements in deep and vacuum ultraviolet. VC 2011 American Institute of Physics. [doi:10.1063/1.3664094]
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Lundin A. A., Zobov V. E.
Заглавие : Order dependence of the profile of the intensities of multiple-quantum coherences
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2015. - Vol. 120, Is. 5. - P.762-771. - ISSN 1063, DOI 10.1134/S1063776115040093. - ISSN 10906509(eISSN)
Примечания : Cited References:62
Предметные рубрики: PARAMAGNETIC SPIN SYSTEMS
FREE-INDUCTION DECAY
NMR-SPECTRA
AUTOCORRELATION FUNCTIONS
FLUCTUATION SPECTRUM
TEMPERATURE DYNAMICS
LINE-SHAPE
SOLIDS
IRREVERSIBILITY
BEHAVIOR
Аннотация: A modification of the widespread phenomenological model theory of multiple-quantum (MQ) nuclear magnetic resonance spectra of a single cluster of correlated spins has been developed. In contrast to the mentioned theory, the size distribution of such clusters has been consistently taken into account. To obtain the distribution, solutions for the amplitudes of the expansion in the complete set of orthogonal operators are used. Expressions specifying the dependence of the profile of the intensities of MQ coherences on their number n (order) have been obtained. The total form of the dependence has been evaluated by means of the numerical implementation of the resulting expressions. The asymptotic expressions for large n values (wings of the spectrum) have been obtained analytically by the saddle-point method. It has been shown that the dependence under study has a Gaussian central part and exponential wings. The results obtained are in agreement with the previous calculations for some model systems and existing experimental data.
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Kucherov M. M.
Заглавие : On the concentration dependence of wings of spectra of spin correlation functions of diluted heisenberg paramagnets
Место публикации : JETP Letters. - 2016. - Vol. 103, Is. 11. - P.687-691. - ISSN 0021-3640, DOI 10.1134/S0021364016110138. - ISSN 1090-6487(eISSN)
Примечания : Cited References:26
Предметные рубрики: HIGH-TEMPERATURES
AUTOCORRELATION FUNCTION
SINGULAR POINT
SYSTEMS
TIME
COORDINATE
LATTICE
Аннотация: Singular points of the autocorrelation function on the imaginary time axis that is averaged over the location of spins in the magnetically dilute spin lattice with isotropic spin-spin interaction at a high temperature have been studied. For the autocorrelation function in the approximation of the self-consistent fluctuating local field, nonlinear integral equations have been proposed which reflect the separation of the inhomogeneous spin systems into close spins and other spins. The coordinates of the nearest singular points have been determined in terms of the radius of convergence of the expansion in powers of time, the coefficients of which have been calculated from recurrence equations. It has been shown that the coordinates of singular points and, consequently, the wings of the autocorrelation function spectrum at strong magnetic dilution are determined by the modulation of the local field by the nearest pairs of spins leading to its logarithmic concentration dependence.
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8.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Zobov V. E., Kucherov M. M.
Заглавие : On the concentration dependence of the high-frequency asymptotics of spin correlation functions in a dilute Heisenberg paramagnet
Коллективы : Euro-Asian Symposium "Trends in MAGnetism", "Trends in MAGnetism", Euro-Asian Symposium, Институт физики им. Л.В. Киренского Сибирского отделения РАН
Место публикации : VI Euro-Asian Symposium "Trends in MAGnetism" (EASTMAG-2016): abstracts/ ed.: O. A. Maksimova, R. D. Ivantsov. - Krasnoyarsk: KIP RAS SB, 2016. - Ст.P5.7. - P.279. - ISBN 978-5-904603-06-9 (Шифр -478014040)
Примечания : References: 5
Ключевые слова (''Своб.индексиров.''): disordered spin system--spin dynamics--autocorrelation function--singular points--wings of spectrum
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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Kucherov M. M.
Заглавие : Concentration dependence of the wings of a dipole-broadened magnetic resonance line in magnetically diluted lattices
Место публикации : J. Exp. Theor. Phys.: Maik Nauka-Interperiodica Publishing, 2017. - Vol. 124, Is. 1. - P.151-158. - ISSN 10637761 (ISSN), DOI 10.1134/S106377611615005X
Примечания : Cited References: 34
Ключевые слова (''Своб.индексиров.''): drug interactions--magnetic fields--magnetic resonance--magnetism--nonlinear equations--optical systems--autocorrelation functions--concentration dependence--high-frequency asymptotics--local field approximations--magnetic resonance line--modulation frequencies--strong static magnetic fields--time autocorrelation functions--autocorrelation
Аннотация: The singularities of the time autocorrelation functions (ACFs) of magnetically diluted spin systems with dipole–dipole interaction (DDI), which determine the high-frequency asymptotics of autocorrelation functions and the wings of a magnetic resonance line, are studied. Using the self-consistent fluctuating local field approximation, nonlinear equations are derived for autocorrelation functions averaged over the independent random arrangement of spins (magnetic atoms) in a diamagnetic lattice with different spin concentrations. The equations take into account the specificity of the dipole–dipole interaction. First, due to its axial symmetry in a strong static magnetic field, the autocorrelation functions of longitudinal and transverse spin components are described by different equations. Second, the long-range type of the dipole–dipole interaction is taken into account by separating contributions into the local field from distant and near spins. The recurrent equations are obtained for the expansion coefficients of autocorrelation functions in power series in time. From them, the numerical value of the coordinate of the nearest singularity of the autocorrelation function is found on the imaginary time axis, which is equal to the radius of convergence of these expansions. It is shown that in the strong dilution case, the logarithmic concentration dependence of the coordinate of the singularity is observed, which is caused by the presence of a cluster of near spins whose fraction is small but contribution to the modulation frequency is large. As an example a silicon crystal with different 29Si concentrations in magnetic fields directed along three crystallographic axes is considered. © 2017, Pleiades Publishing, Inc.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Kucherov M. M.
Заглавие : Exponential Bound for the Heating Rate of Periodically Driven Spin Systems
Место публикации : J. Exp. Theor. Phys. - 2019. - Vol. 128, Is. 4. - P.641-649. - ISSN 1063-7761, DOI 10.1134/S1063776119030130. - ISSN 1090-6509(eISSN)
Примечания : Cited References: 42
Предметные рубрики: AUTOCORRELATION FUNCTIONS
HEISENBERG PARAMAGNET
FLUCTUATION SPECTRUM
Аннотация: For the nuclear spin system of a solid in the presence of an inhomogeneous magnetic field, we have found a rigorous bound for the heating rate of the system under the action of a high-frequency magnetic field, which is applied, for example, to create effective Hamiltonians. We consider the autocorrelation function (ACF) of a spin rotating in a local field whose fluctuations are specified by a Gaussian random process. The correlation function of a random field is taken as the sum of a static inhomogeneous contribution and a time-dependent contribution expressed self-consistently via the spin ACF. The ACF singularities on the imaginary time axis whose coordinates determine the exponents of exponential asymptotics in the high-frequency domain are investigated. The dependences of the coordinates on field inhomogeneity for various approximations have been derived. The wing of the ACF spectrum in the cumulant approximation is shown to serve as a rigorous upper bound for the wing of the ACF spectrum and, consequently, for the heating rate of the system when subjected to variable magnetic fields. We have established that randomly distributed inhomogeneous magnetic fields increase the wings of the ACF spectra and, thus, speed up the system's heating.
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