Труды сотрудников института физики

[Рукопись] : дис. на соиск. уч. степени д-ра физ.-мат. наук : 01.04.07 / М. А. Попов ; Краснояр. гос. ун-т, Рос. акад. наук, Сиб. отд-ние, Ин-т физики им. Л.В. Киренского. - Красноярск, 2000. - 143 л. - Библиогр.: 153 назв. . -

ГРНТИ

29.19.37

29.19.49

ББК В373.3я031


Держатели документа:
Библиотека Института физики им. Л. В. Киренского СО РАН
Доп.точки доступа:
Popov M. A.; Красноярский государственный университетРоссийская академия наук; Сибирское отделение РАН; Институт физики им. Л.В. Киренского Сибирского отделения РАН
Экземпляры всего: 1
ДС (1)
Свободны: ДС (1)

[Рукопись] : дис. на соиск. уч. степени канд. физ.-мат. наук : 01.04.03 : защищена 14.06.1985 / М. А. Попов ; науч. рук. Ю. Г. Кубарев ; Акад. наук СССР, Сиб. отд-ние, Ин-т физики им. Л.В. Киренского. - Красноярск, 1985. - 94 л. - Библиогр.: 84 назв. -

ГРНТИ

29.19.15

29.19.37

ББК В373.3я031 + В375.1я031


Держатели документа:
Библиотека Института физики им. Л. В. Киренского СО РАН
Доп.точки доступа:
Кубарев, Юрий Григорьевич \науч. рук. .\; Popov M. A.; Академия наук СССР; Сибирское отделение АН СССРИнститут физики им. Л.В. Киренского Сибирского отделения АН СССР
Экземпляры всего: 1
ДС (1)
Свободны: ДС (1)

/ M. A. Popov [et al.] // IEEE Trans. Magn. - 2014. - Vol. 50, Is. 6. - Ст. 4004507, DOI 10.1109/TMAG.2014.2298498. - Cited References: 34 . - ISSN 0018-9464. - ISSN 1941-0069РУБ Engineering, Electrical & Electronic + Physics, Applied

Аннотация: Dielectric resonances in the 37-42 GHz frequency band in the single crystal barium hexaferrite that occur well below the ferromagnetic resonance (FMR) have been investigated. Sample dimensions have been chosen so that the mode frequency is lower than the spin-wave excitation (in this case, the natural domain resonance) frequency. Such dielectric mode frequencies, being a function of both permittivity and permeability, are magnetic field H tunable. Here, we report on below-FMR magnetodielectric resonance (MDR) axially magnetized barium hexaferrites and their H-tuning characteristics. Our studies reveal H-tuning by up to 2.5 GHz and the tuning is the largest when the ferrite is in a magnetically unsaturated state. A theory for the MDR is presented and a fairly good agreement between experimental data and theory has been obtained. Tunable millimeter wave phase shifters and isolators utilizing the below-FMR dielectric resonances have been demonstrated.

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Держатели документа:
Taras Shevchenko Natl Univ Kyiv, Radiophys Dept, UA-01601 Kiev, Ukraine
Oakland Univ, Dept Phys, Rochester, MI 48309 USA
Russian Acad Sci, LV Kirensky Phys Inst, Krasnoyarsk 660036, Russia

Доп.точки доступа:
Popov, M. A.; Zavislyak, I. V.; Movchan, N. N.; Gudim, I. A.; Гудим, Ирина Анатольевна; Srinivasan, G.

/ M. A. Popov, G. A. Petrakovskii, O. A. Bolsunovskaya // Phys. Solid State. - 2008. - Vol. 50, Is. 5. - P. 909-912, DOI 10.1134/S106378340805017X. - Cited References: 6 . - ISSN 1063-7834РУБ Physics, Condensed Matter

Аннотация: A stepwise transition from one incommensurate state of the spin system of a copper metaborate crystal to another incommensurate state was previously revealed using neutron scattering in an applied magnetic field. In this paper, the new state is interpreted as a combination of a commensurate state of one spin subsystem and an incommensurate state of another spin subsystem of the crystal.

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Держатели документа:
[Popov, M. A.] Siberian Fed Univ, Krasnoyarsk 660041, Russia
[Petrakovskii, G. A.
Bolsunovskaya, O. A.] Russian Acad Sci, LV Kirensky Phys Inst, Siberian Branch, Krasnoyarsk 660036, Russia
ИФ СО РАН
Siberian Federal University, Svobodnyi pr. 79, Krasnoyarsk, 660041, Russian Federation
Kirensky Institute of Physics, Siberian Branch, Russian Academy of Sciences, Akademgorodok, Krasnoyarsk, 660036, Russian Federation

Доп.точки доступа:
Petrakovskii, G. A.; Петраковский, Герман Антонович; Bolsunovskaya, O. A.

/ G. A. Petrakovskii [et al.] // Phys. Solid State. - 2007. - Vol. 49, Is. 7. - P. 1315-1320, DOI 10.1134/S1063783407070207. - Cited References: 21 . - ISSN 1063-7834РУБ Physics, Condensed Matter

Аннотация: This paper reports on the results of measurements of the magnetic susceptibility, heat capacity, neutron scattering, muon spin relaxation, and electron paramagnetic resonance in Cu3B2O6 for the study of the ground state of the spin system of this compound. The results obtained suggest that, at a temperature of 10 K, the spin subsystem of the crystal, which consists of single spins and clusters of pairs and fours of spins interacting with one another, undergoes a transition to a state representing a superposition of the singlet (for clusters) and magnetically ordered (for single spins) states.

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Держатели документа:
LV Kirenskii Inst Phys, Siberian Div, Russian Acad Sci, Krasnoyarsk 660036, Russia
Paul Scherrer Inst, Villigen, Switzerland
Polish Acad Sci, Inst Phys, PL-02668 Warsaw, Poland
ИФ СО РАН
Kirensky Institute of Physics, Siberian Division, Russian Academy of Sciences, Akademgorodok, Krasnoyarsk 660036, Russian Federation
Paul-Scherrer Institute, Villigen, Switzerland
Institute of Physics, Polish Academy of Sciences, Warsaw 02-668, Poland

Доп.точки доступа:
Petrakovskii, G. A.; Петраковский, Герман Антонович; Bezmaternykh, L. N.; Безматерных, Леонард Николаевич; Bayukov, O. A.; Баюков, Олег Артемьевич; Popov, M. A.; Schefer, J.; Neidermayer, C.; Aleshkevich, P.; Szymczak, R.

/ Y. . Yasuda [et al.] // J. Phys.: Condens. Matter. - 2007. - Vol. 19: International Conference on Highly Frustrated Magnetism (AUG 15-19, 2006, Osaka, JAPAN), Is. 14. - Ст. 145277, DOI 10.1088/0953-8984/19/14/145277. - Cited References: 10 . - ISSN 0953-8984РУБ Physics, Condensed Matter

Аннотация: The material CuB2O4 presents a variety of phases in the B - T phase diagram, caused by the frustration and the Dzialoshinskii - Moriya interaction. In order to investigate the nature of the phase transitions, a B-11- NMR experiment on CuB2O4 has been performed under an applied magnetic field along the a- axis down to 0.4 K. A new incommensurate - incommensurate phase transition has been found at 0.8 K under a field of 0.5 T. Further, another phase transition has been observed at 4.7 K under a field of about 2 T, which is consistent with the transition reported by the neutron diffraction experiment.

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Держатели документа:
Univ Fukui, Dept Appl Phys, Fukui 9108507, Japan
Japan Adv Inst Sci & Technol, Ishikawa 9231292, Japan
RAS, SB, Inst Phys, Krasnoyarsk 660036, Russia
ИФ СО РАН
Department of Applied Physics, University of Fukui, Fukui 910-8507, Japan
Japan Advanced Institute of Science and Technology, Ishikawa 923-1292, Japan
Institute of Physics, SB RAS, 660036 Krasnoyarsk, Russian Federation

Доп.точки доступа:
Yasuda, Y.; Nakamura, H.; Fujii, Y.; Kikuchi, H.; Chiba, M.; Yamamoto, Y.; Hori, H.; Petrakovskii, G. A.; Петраковский, Герман Антонович; Popov, M. A.; Bezmaternykh, L. N.

/ V. E. Zobov, M. A. Popov // Theor. Math. Phys. - 2005. - Vol. 144, Is. 3. - P. 1361-1371, DOI 10.1007/s11232-005-0165-z. - Cited References: 19 . - ISSN 0040-5779РУБ Physics, Multidisciplinary + Physics, Mathematical

Аннотация: In the Eden model, we investigate how the tree growth parameter depends on the space dimension d for face-centered hypercubic lattices. We find the first three terms of the 1/d-expansion for this parameter directly from the generating function without calculating the number of trees because the growth parameter is the reciprocal coordinate of the singular point of the tree generating function. The same growth parameter was calculated by computer experiment where the ratios between the numbers of trees without intersections and trees without restrictions in the dimensions 3, 4, 6, 8, and 10 were estimated by the Monte Carlo method on face-centered cubic lattices. The results of the two methods agree well. Comparing with the previously performed computer experiment for simple hypercubic lattices, we observe that the values of the singular exponents for the tree generating functions are close for two different types of lattices.

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Держатели документа:
RAS, Siberian Branch, Kirenskii Inst Phys, Novosibirsk, Russia
Krasnoyarsk State Univ, Krasnoyarsk, Russia
ИФ СО РАН
Kirenskii Institute of Physics, Siberian Branch, RAS, Russian Federation
Krasnoyarsk State University, Krasnoyarsk, Russian Federation

Доп.точки доступа:
Popov, M. A.; Зобов, Владимир Евгеньевич

/ V. E. Zobov, M. A. Popov // J. Exp. Theor. Phys. - 2005. - Vol. 100, Is. 4. - P. 775-783, DOI 10.1134/1.1926438. - Cited References: 24 . - ISSN 1063-7761РУБ Physics, Multidisciplinary

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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Держатели документа:
Russian Acad Sci, Siberian Div, Kirenskii Inst Phys, Krasnoyarsk 660036, Russia
Krasnoyarsk State Univ, Krasnoyarsk 660041, Russia
ИФ СО РАН
Kirenskii Institute of Physics, Siberian Division, Russian Academy of Sciences, Akademgorodok, Krasnoyarsk, 660036, Russian Federation
Krasnoyarsk State University, Krasnoyarsk, 660041, Russian Federation

Доп.точки доступа:
Popov, M. A.; Зобов, Владимир Евгеньевич

/ M. A. Popov, G. A. Petrakovskii, V. I. Zinenko // Phys. Solid State. - 2004. - Vol. 46, Is. 3. - P. 491-497, DOI 10.1134/1.1687867. - Cited References: 9 . - ISSN 1063-7834РУБ Physics, Condensed Matter

Аннотация: Symmetry analysis is performed for the magnetic subsystem of copper metaborate, and a phenomenological model is proposed with two two-component order parameters that correspond to ferromagnetism and antiferromagnetism vectors lying in the tetragonal plane of this crystal. Owing to the I (4) over bar 2d space group of symmetry of this crystal, the thermodynamic potential contains the Lifshitz invariant having the form of an antisymmetric product of the order parameters and their spatial derivatives. Analysis of this model shows that the temperatures of ordering in the magnetic subsystem and of the formation of a spiral structure in it can be different. This fact allows numerical calculation of the temperature dependences of the spiral wave vector, magnetization, and intensities of first- and third-order magnetic satellites in the incommensurate phase that arise in neutron elastic scattering, as well as the field dependence of the magnetization. The experimental data, including a magnetic-field-temperature phase diagram, are satisfactorily described. The parameters of the phenomenological thermodynamic potential of the magnetic subsystem of copper metaborate are estimated. (C) 2004 MAIK "Nauka / Interperiodica".

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Держатели документа:
Krasnoyarsk State Univ, Krasnoyarsk 660041, Russia
Russian Acad Sci, LV Kirensky Phys Inst, Siberian Div, Krasnoyarsk 660036, Russia
ИФ СО РАН
Krasnoyarsk State University, Krasnoyarsk, 660041, Russian Federation
Kirensky Institute of Physics, Siberian Division, Russian Academy of Sciences, Akademgorodok, Krasnoyarsk, 660036, Russian Federation

Доп.точки доступа:
Petrakovskii, G. A.; Петраковский, Герман Антонович; Zinenko, V. I.; Зиненко, Виктор Иванович

/ V. E. Zobov, M. A. Popov // Theor. Math. Phys. - 2003. - Vol. 136, Is. 3. - P. 1297-1311, DOI 10.1023/A:1025603416535. - Cited References: 25 . - ISSN 0040-5779РУБ Physics, Multidisciplinary + Physics, Mathematical

Аннотация: We investigate generating functions for equipped trees composed of double bonds of two sorts on a hypercubic lattice of dimension d with built-in fragments. Rules for constructing these clusters are chosen to ensure the estimate for coefficients of power series in time for the longitudinal and transverse autocorrelation functions of the spin system with axially symmetric interaction. We derive a system of two equations for the tree-generating functions and an equation for the generating functions of chains leading from the root to a fragment in a tree using the Bethe approximation and under the condition that mainly bonds of one sort are taken into account. For the face-centered hypercubic lattice, we find the First terms of the 1/d expansion for the coordinate of the singular point of the generating function in both the anisotropic and the isotropic cases taking fragments in the forms of a triangle from four bonds and a four-fold bound pair into account. The obtained result is written in terms of ratios of lattice sums and is generalized to nuclear spin systems with dipole-dipole interaction. The theoretical value of the singular-point coordinate agrees well with the experimental value calculated from the tail of the absorption spectrum of the nuclear magnetic resonance in a barium fluoride monocrystal.

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Держатели документа:
Russian Acad Sci, Siberian Branch, LV Kirensky Phys Inst, Novosibirsk, Russia
Krasnoyarsk State Univ, Krasnoyarsk, Russia
ИФ СО РАН
Kirenskii Institute of Physics, Siberian Branch, RAS, Russian Federation
Krasnoyarsk State University, Krasnoyarsk, Russian Federation

Доп.точки доступа:
Popov, M. A.; Зобов, Владимир Евгеньевич

/ A. I. Pankrats [et al.] // JETP Letters. - 2003. - Vol. 78, Is. 9. - P. 569-573, DOI 10.1134/1.1641486. - Cited References: 15 . - ISSN 0021-3640РУБ Physics, Multidisciplinary

Аннотация: The static and resonance properties of copper metaborate CuB2O4 were experimentally studied in a magnetic field applied in the crystal tetragonal plane. The field-induced second-order phase transition to a weakly ferromagnetic state was observed in the temperature range 10-20 K. The low-field state is characterized by the absence of spontaneous moment, and it represents, presumably, a long-period helicoid. At temperatures below 2 K, two sequential first-order phase transitions were observed. They were accompanied by jumps in resonance absorption with a hysteresis upon changing field-scan direction. These transitions can be caused by the transformation of the incommensurate spin structure into the helicoidal states with periods commensurate with the lattice translation period. (C) 2003 MAIK "Nauka / Interperiodica".

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Держатели документа:
Russian Acad Sci, LV Kirensky Phys Inst, Siberian Div, Krasnoyarsk 660036, Russia
Russian Acad Sci, PL Kapitza Phys Problems Inst, Moscow 117334, Russia
Polish Acad Sci, Inst Phys, PL-02668 Warsaw, Poland
ИФ СО РАН
Kirenskii Institute of Physics, Siberian Division, Russian Academy of Sciences, Krasnoyarsk, Akademgorodok, 660036, Russian Federation
Kapitza Institute for Physical Problems, Russian Academy of Sciences, ul. Kosygina 2, Moscow, 117334, Russian Federation
Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw, Poland

Доп.точки доступа:
Pankrats, A. I.; Панкрац, Анатолий Иванович; Petrakovskii, G. A.; Петраковский, Герман Антонович; Popov, M. A.; Sablina, K. A.; Саблина, Клара Александровна; Prozorova, L. A.; Sosin, S. S.; Szimczak, G.; Szimczak, R.; Baran, M.

/ V. E. Zobov, M. A. Popov // J. Exp. Theor. Phys. - 2003. - Vol. 97, Is. 1. - P. 78-84, DOI 10.1134/1.1600799. - Cited References: 22 . - ISSN 1063-7761РУБ Physics, Multidisciplinary

Аннотация: The hypothesis concerning the existence of singular points on the imaginary time axis for a correlation function of a system with the dipole-dipole interaction of nuclear spins of a crystal is verified. Within the framework of the self-consistent fluctuating field theory taking into account the principal corrections related to the correlation of local fields, a result for this coordinate is obtained in terms of the ratios of lattice sums. Experimental values of this coordinate are calculated from the wings of the nuclear magnetic resonance absorption spectrum of a BaF2 crystal for the magnetic field directions along the three crystallographic axes. Good agreement of the theoretical and experimental results justifies this hypothesis. (C) 2003 MAIK "Nauka / Interperiodica".

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Держатели документа:
Russian Acad Sci, Siberian Div, LV Kirensky Phys Inst, Krasnoyarsk 660036, Russia
Krasnoyarsk State Univ, Krasnoyarsk 660041, Russia
ИФ СО РАН
Kirenskii Institute of Physics, Siberian Division, Russian Academy of Sciences, Akademgorodok, Krasnoyarsk, 660036, Russian Federation
Krasnoyarsk State University, Krasnoyarsk, 660041, Russian Federation

Доп.точки доступа:
Popov, M. A.; Зобов, Владимир Евгеньевич

/ G. A. Petrakovskii [et al.] // Low Temp. Phys. - 2002. - Vol. 28, Is. 8-9. - P. 606-612 ; Физика низких температур, DOI 10.1063/1.1511704. - Cited References: 17 . - ISSN 1063-777XРУБ Physics, Applied

Аннотация: The results of experimental research on the magnetic and resonance properties, heat capacity, muon spin relaxation, and neutron scattering of single-crystal copper metaborate CuB2O4 are reviewed. The results of a symmetry analysis and of modeling by the method of the phenomenological thermodynamic potential are presented. The magnetic structure of the crystal in various temperature intervals of the magnetic ordering region is discussed. (C) 2002 American Institute of Physics.

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Держатели документа:
Russian Acad Sci, LV Kirensky Phys Inst, Siberian Branch, Krasnoyarsk 660036, Russia
Paul Scherrer Inst, CH-6232 Villigen, Switzerland
Swiss Fed Inst Technol, Lab Neutron Scattering, CH-6232 Villigen, Switzerland
Inst Max Von Laue Paul Langevin, F-38042 Grenoble 9, France
ИФ СО РАН
L. V. Kirenskii Institute of Physics, Siberian Branch, Russian Academy of Sciences, Akademgorodok, 660036 Krasnoyarsk, Russian Federation
Laboratory for Neutron Scattering, ETH Zurich, Paul Scherrer Institute, CH-6232 Villigen PSI, Switzerland
Institut Laue-Langevin, 38042 Grenoble, Cedex 9, France

Доп.точки доступа:
Petrakovskii, G. A.; Петраковский, Герман Антонович; Pankrats, A. I.; Панкрац, Анатолий Иванович; Popov, M. A.; Balaev, A. D.; Балаев, Александр Дмитриевич; Velikanov, D. A.; Великанов, Дмитрий Анатольевич; Vorotynov, A. M.; Воротынов, Александр Михайлович; Sablina, K. A.; Саблина, Клара Александровна; Roessli, B.; Schefer, J.; Amato, A.; Staub, U.; Boehm, M.; Ouladdiaf, B.

/ V. E. Zobov, M. A. Popov // Theor. Math. Phys. - 2002. - Vol. 131, Is. 3. - P. 862-872, DOI 10.1023/A:1015935809388. - Cited References: 19 . - ISSN 0040-5779РУБ Physics, Multidisciplinary + Physics, Mathematical

Аннотация: Using the d(-1) expansion method (d is the space dimension), we estimate the coordinate of the time-dependent autocorrelation function singular point on the imaginary time axis for the spin 1/2 Heisenberg model on a simple hypercubic lattice at high temperatures. We represent the coefficients of the time expansion (the spectral moments) for the autocorrelation function as the sums of the weighted lattice figures in which the trees constructed from the double bonds give the leading contributions with respect to d(-1) and the same trees with the built-in squares from six bonds or diagrams with the fourfold bonds give the contribution of the next-to-leading order. We find the corrections to the coordinate of the autocorrelation function singular point that are due to the latter contributions.

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Держатели документа:
RAS, Siberian Branch, LV Kirensky Phys Inst, Krasnoyarsk 660036, Russia
Krasnoyarsk State Univ, Krasnoyarsk, Russia
ИФ СО РАН
Kirensky Institute of Physics, Siberian Branch, RAS, Krasnoyarsk, Russian Federation
Kirensky State University, Krasnoyarsk, Russian Federation

Доп.точки доступа:
Popov, M. A.; Зобов, Владимир Евгеньевич

/ V. E. Zobov, M. A. Popov // Theor. Math. Phys. - 2001. - Vol. 126, Is. 2. - P. 270-279, DOI 10.1023/A:1005260114182. - Cited References: 17 . - ISSN 0040-5779РУБ Physics, Multidisciplinary + Physics, Mathematical

Аннотация: We use the Monte Carlo method to compute the number of trees with n edges in the Eden model on d-dimensional simple cubic lattices for d = 2, 3, 4, 6, 8, 10. We compare these numbers with the exact data derived by the enumeration method up to n = 12 on the square lattice and up to n = 10 on the cubic lattice. We find that for d greater than or equal to 3, the computed values of the growth parameter for trees agree with the values that we derived earlier by the expansion in inverse powers of 2d - 1.

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Держатели документа:
RAS, Siberian Branch, Kirenskii Phys Inst, Krasnoyarsk, Russia
Krasnoyarsk State Univ, Krasnoyarsk, Russia
ИФ СО РАН
Kirenskii Physics Institute, Siberian Branch, RAS, Krasnoyarsk, Russian Federation
Krasnoyarsk State University, Krasnoyarsk, Russian Federation

Доп.точки доступа:
Popov, M. A.; Зобов, Владимир Евгеньевич

/ G. A. Petrakovskii [et al.] // J. Exp. Theor. Phys. - 2001. - Vol. 93, Is. 4. - P. 809-814, DOI 10.1134/1.1420450. - Cited References: 10 . - ISSN 1063-7761РУБ Physics, Multidisciplinary

Аннотация: Based on the experimental data on copper metaborate single crystals obtained in X-ray and neutron diffraction studies and heat capacity, magnetic susceptibility, and muon spin relaxation measurements, a phenomenological theory of the incommensurate magnetic structure of this crystal was developed. Considering the space group of the crystal, I (4) over bar 2d, Lifshits invariants were included into its thermodynamic potential. An analysis showed that magnetic structure formation at 10-20 K was dominated by the subsystem of copper spins in 4b unit cell sites. Below 10 K, the role played by the magnetic subsystem of copper spins in 8d unit cell sites in the formation of the magnetic structure of copper metaborate substantially increased. This caused a sharp increase in the wave vector of the incommensurate structure as temperature lowered. Numerical simulation of the temperature dependence of the wave vector of the helix and the heat capacity of the crystal gave a satisfactory description of the experimental data. This simulation was used to estimate the parameters of the phenomenological thermodynamic potential of the magnetic system of copper metaborate. (C) 2001 MAIK "Nauka/Interperiodica".

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Держатели документа:
Russian Acad Sci, Siberian Div, Kirenskii Inst Phys, Krasnoyarsk 660036, Russia
Krasnoyarsk State Univ, Krasnoyarsk 660041, Russia
ETH Zurich, Neutron Scattering Lab, CH-5232 Villigen, Switzerland
Paul Scherrer Inst, CH-5232 Villigen, Switzerland
Inst Max Von Laue Paul Langevin, F-38042 Grenoble 9, France
ИФ СО РАН

Доп.точки доступа:
Petrakovskii, G. A.; Петраковский, Герман Антонович; Popov, M. A.; Roessli, B.; Ouladdiaf, B.

/ V. E. Zobov, M. A. Popov // J. Stat. Phys. - 1999. - Vol. 97, Is. 3-4. - P. 793-802, DOI 10.1023/A:1004675527713. - Cited References: 17 . - ISSN 0022-4715РУБ Physics, Mathematical

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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Держатели документа:
LV Kirensky Phys Inst, Siberian Branch, Krasnoyarsk 660036, Russia
Krasnoyarsk State Univ, Krasnoyarsk 660041, Russia
ИФ СО РАН

Доп.точки доступа:
Popov, M. A.; Зобов, Владимир Евгеньевич

/ V. E. Zobov [et al.] // J. Exp. Theor. Phys. - 1999. - Vol. 88, Is. 1. - P. 157-167, DOI 10.1134/1.558778. - Cited References: 36 . - ISSN 1063-7761РУБ Physics, Multidisciplinary

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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Держатели документа:
Russian Acad Sci, LV Kirensky Phys Inst, Siberian Div, Krasnoyarsk 660036, Russia
Krasnoyarsk State Univ, Krasnoyarsk 660041, Russia
Russian Acad Sci, Siberian Branch, Inst Chem & Chem Technol, Krasnoyarsk 660036, Russia
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Доп.точки доступа:
Zobov, V. E.; Зобов, Владимир Евгеньевич; Ivanov, Y. N.; Иванов, Юрий Николаевич; Popov, M. A.; Livshits, A. I.

/ V. E. Zobov, M. A. Popov // Theor. Math. Phys. - 1997. - Vol. 112, Is. 3. - P. 1182-1191, DOI 10.1007/BF02583049. - Cited References: 22 . - ISSN 0040-5779РУБ Physics, Multidisciplinary + Physics, Mathematical

Аннотация: The convergence of series in powers of time for spin autocorrelation functions of the Heisenberg magnet are investigated at infinite temperatures on lattices of different dimensions d. The calculation data available at the present time for the coefficients of these series are used to estimate the corresponding radii of convergence, whose growth with decreasing d is revealed and explained in a self-consistent approximation. To this end, a simplified nonlinear equation corresponding to this approximation is suggested and solved for the autocorrelation function of a system with an arbitrary number Z of nearest neighbors. The coefficients of the expansion in powers of time for the solution are represented in the form of trees on the Bethe lattice with the coordination number Z. A computer simulation method is applied to calculate the expansion coefficients for trees embedded in square, triangular, and simple cubic lattices under the condition that the intersection of tree branches is forbidden. It is found that the excluded volume effect that manifests itself in a decrease in these coefficients and in an increase in the coordinate and exponent of the singularity of the autocorrelation function on the imaginary time axis is intensified with decreasing lattice dimensions.

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Держатели документа:
Russian Acad Sci, LV Kirensky Phys Inst, Siberian Div, Krasnoyarsk, Russia
Krasnoyarsk State Univ, Krasnoyarsk, Russia
ИФ СО РАН

Доп.точки доступа:
Popov, M. A.; Зобов, Владимир Евгеньевич

/ M. A. Popov // Theor. Math. Phys. - 1990. - Vol. 83, Is. 3. - P. 658-663, DOI 10.1007/BF01018036. - Cited References: 7 . - ISSN 0040-5779РУБ Physics, Multidisciplinary + Physics, Mathematical

Аннотация: The infinite hierarchy of equations for the cumulants of the correlation functions of the longitudinal spin components in the Ising model with long-range interaction corresponding to a Gaussian form of the spectral density is investigated. The invariance of the cumulants with respect to permutation of the vertices is used to decouple the hierarchy. A phase transition of the second kind is described by the obtained system of equations for the cumulants of the first three orders in a three-dimensional model.

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