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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Lundin A. A.
Заглавие : Modeling multiparticle coherences in solid-state nuclear spin systems using infinite-range interaction
Место публикации : Theor. Math. Phys. - 2004. - Vol. 141, Is. 3. - P.1737-1749. - ISSN 0040-5779, DOI 10.1023/B:TAMP.0000049765.41265.dd
Примечания : Cited References: 24
Предметные рубрики: MULTIPLE-QUANTUM DYNAMICS
NMR-SPECTRA
TEMPERATURE DYNAMICS
SHAPE
VAN
Ключевые слова (''Своб.индексиров.''): multipulse method--dipole-dipole interaction--multispin coherence--time correlation function--rotating reference frame--dipole-dipole interaction--multipulse method--multispin coherence--rotating reference frame--time correlation function
Аннотация: Using the exactly solvable model known in statistical physics as the infinite-range interaction model (the van der Waals model), we obtain expressions for the hierarchy of multispin multiquantum time correlation functions for a solid-state paramagnetic nuclear spin system with magnetic dipole-dipole interaction between nuclei. These functions are observed experimentally using contemporary multiquantum NMR spectroscopy methods. We write the complete set of orthogonal multispin operators explicitly and find the time dependence for amplitudes of multiparticle time correlation functions. The proposed model describes the behavior of multiparticle correlation functions well, at least for not very large numbers n of expansion harmonics. The theoretical results agree well with the experimental data obtained for hexamethylbenzol.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Ivanov Y. N., Popov M. A., Livshits A. I.
Заглавие : Orientational dependence of the tails of dipole-broadened NMR spectra in crystals
Место публикации : J. Exp. Theor. Phys.: AMER INST PHYSICS, 1999. - Vol. 88, Is. 1. - P157-167. - ISSN 1063-7761, DOI 10.1134/1.558778
Примечания : Cited References: 36
Предметные рубрики: NUCLEAR-DOUBLE-RESONANCE
FLUCTUATION SPECTRUM
CROSS-RELAXATION
SOLIDS
DIFFUSION
MEMORY
SHAPE
Аннотация: This paper describes experimental and theoretical studies of the tails of the dipole-broadened nuclear magnetic resonance (NMR) absorption spectra of F-19 in isomorphic single crystals of BaF2 and CaF2 with the magnetic field directed along three crystallographic axes. The results obtained by directly measuring the derivative of the tail of the NMR absorption spectrum and the falloffs of the Engelsberg-Lowe free precession after Fourier transformation qualitatively agree. It is shown that the shape of the tail is well described by an exponential function in which the orientational dependence of the exponent does not reduce to variation of the second moment. The observed shape of the tail and the orientational dependence of its parameters are explained on the basis of a self-consistent fluctuating-local-field theory. Nonlinear integral equations are derived for the correlation functions, taking into account the changes of the actual number of nearest neighbors caused by the anisotropy of the dipole-dipole interaction and the contribution of lattice sums with loops. The equations are solved numerically. Good agreement is obtained for the computed dropoffs of the free precession, the NMR spectra, and the cross-polarization rates with the experimental results. (C) 1999 American Institute of Physics. [S1063-7761(99)02401-4].
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Lundin A. A., Zobov V. E.
Заглавие : Solid-state NMR free induction decay, simulated by the system of classical magnetic moments and quantum correlations
Коллективы : [AAAA-A19-119012890064-7]
Место публикации : Russ. J. Phys. Chem. B. - 2021. - Vol. 15, Is. 5. - P.839-847. - ISSN 1990-7931, DOI 10.1134/S1990793121050079. - ISSN 1990-7923(eISSN)
Примечания : Cited References: 34. - This study was carried out as part of state assignment 0082-2019-0001 (registration number AAAA-A19-119012890064-7)
Предметные рубрики: HIGH-TEMPERATURE DYNAMICS
HEISENBERG-MODEL
SPIN SIMULATIONS
SHAPE
Аннотация: In the past decade, nuclear magnetic resonance (NMR) has been actively used to study the basic principles of quantum computers. It is assumed that quantum correlations play a significant role in their performance. They exist at both low and high temperatures. At the same time, the time correlation functions of nuclear spin systems of solids determine the observed signals in traditional NMR implementations. The separation of such signals into quantum and classical components has not previously been carried out and will be performed in this study for the most important of the correlational functions observed in magnetic resonance: the free induction decay (FID).
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ignatchenko V. A., Edelman I. S., Petrov D. A.
Заглавие : Magnetostatic fields in planar assemblies of magnetic nanoparticles
Коллективы :
Место публикации : Phys. Rev. B: AMER PHYSICAL SOC, 2010. - Vol. 81, Is. 5. - Ст.54419. - ISSN 1098-0121, DOI 10.1103/PhysRevB.81.054419
Примечания : Cited References: 25. - This study was supported in part by the Grant from the President of the Russian Federation for leading scientific schools Project No. 3818.2008.3, the State Contract of the Federal Program No. 02.740.11.0220, the RFBR-CNRS Grant No. 07-02-92174, and the State Program "Development of the Scientific Potential of the Higher Education School," Project No 2.1.1/6038. We wish to acknowledge Janis Kliva for the helpful discussion.
Предметные рубрики: SINGLE-DOMAIN PARTICLES
FERROMAGNETIC-RESONANCE
TAPES
SHAPE
Аннотация: Magnetostatic fields are studied in the model of a planar assembly of magnetic particles forming a periodic lattice infinite in the xy plane and finite along the z axis. Two types of lattices are considered: simple cubic and body-centered cubic. Exact analytical expressions of the magnetostatic fields for the magnetization perpendicular and parallel to the xy plane, H(perpendicular to)(x, y, z) and H(parallel to) (x, y, z), are obtained in the form of Fourier series both inside the particles, and in the surrounding matrix. Exact formulas for mean magnetostatic fields inside the particles, (H) over bar (perpendicular to) and (H) over bar (parallel to), are obtained by averaging over the particle volume. A numerical analysis of these formulas shows linear dependences of (H) over bar (perpendicular to) and (H) over bar (parallel to) on the volume filling factor c. A comparison of these exact solutions with the results of earlier works where such dependences were obtained using different approximate approaches, confirms the correctness of some of them. The correctness of methods allowing the estimation of the filling factor c from both magnetic resonance and magnetometric data is also confirmed.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kliava J., Malakhovskii A. V., Edelman I. S., Potseluyko A. M., Petrakovskaja E. A., Melnikova S.V., Zarubina T. V., Petrovskii G., Bruckental Y., Yeshurun Y.
Заглавие : Unusual magnetic transitions and nature of magnetic resonance spectra in oxide glasses containing gadolinium
Место публикации : Phys. Rev. B: AMER PHYSICAL SOC, 2005. - Vol. 71, Is. 10. - Ст.104406. - ISSN 1098-0121, DOI 10.1103/PhysRevB.71.104406
Примечания : Cited References: 40
Предметные рубрики: ELECTRON-PARAMAGNETIC-RESONANCE
BORATE GLASSES
IONS
BEHAVIOR
GD3+
SPECTROSCOPY
SYSTEMS
GD-3+
FIELD
SHAPE
Ключевые слова (''Своб.индексиров.''): gadolinium--glass--lanthanide--oxide--anisotropy--article--chemical structure--concentration response--electron spin resonance--energy--magnetism--molecular physics--nanoparticle--phase transition--refraction index--temperature sensitivity
Аннотация: Magnetic susceptibility, electron paramagnetic resonance (EPR), and optical properties have been studied in a glass system {20La(2)O(3)-22Al(2)O(3)-23B(2)O(3)-35(SiO2+GeO2)} with a part of La2O3 substituted by Gd2O3 in different concentrations. Positive Weiss constants have been found in the more heavily doped glasses and ascribed to clustering of Gd3+ ions. Two magnetic phase transitions at 55 and 12 K were detected and ascribed, respectively, to ferromagnetic and antiferromagnetic clusters containing Gd ions. The overall shape of the EPR spectra shows the presence of clustering at the higher Gd contents. At low temperatures the cluster-related resonance signal is altered in shape, indicating an onset of magnetic anisotropy field. This signal is convincingly fitted to superparamagnetic resonance arising from ferromagnetic nanoparticles. The clustering, depending on the Gd concentration, correlates with a significant shift to lower energies of the strong optical absorption band edge, ascribed to a charge transfer transition between Gd ions. A nonmonotonous change of refractive index with the increase of the Gd content indicates changes in the glass matrix and in Gd cluster structure.
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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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