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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Lundin A. A.
Заглавие : Second moment of multiple-quantum NMR and a time-dependent growth of the number of multispin correlations in solids
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2006. - Vol. 103, Is. 6. - P904-916. - ISSN 1063-7761, DOI 10.1134/S1063776106120089
Примечания : Cited References: 39
Предметные рубрики: NUCLEAR-MAGNETIC-RESONANCE
LINE-SHAPE
SPIN SYSTEMS
DYNAMICS
SPECTRA
COHERENCES
STATE
BEHAVIOR
CRYSTAL
MODEL
Ключевые слова (''Своб.индексиров.''): correlation methods--mathematical models--nuclear magnetic resonance spectroscopy--spectrum analysis--time series analysis--four-spin time correlation--multispin correlations--second moment--time power series--quantum theory
Аннотация: The time evolution of multispin correlations (the growth of the number of correlated spins as a function of time) can be observed directly using the multiple-quantum nuclear magnetic resonance spectroscopy of solids. A quantity related to this number, namely, the second moment n(2)(t) of the intensity distribution of coherences of different orders in the multiple-quantum spectrum can be calculated using the theory proposed in this work. An approach to the calculation of the four-spin time correlation function through which this moment is expressed is developed. The main sequences of contributions in the expansion of this function into a time power series are summed using the approximation of a large number of neighbors both for systems with a secular dipole-dipole interaction and for systems with a nonsecular effective interaction. An exponential dependence of n(2)(t) is obtained. The value of n(2)(t) is additionally calculated using an expansion in terms of orthogonal operators for three model examples corresponding to different limiting realizations of spin systems. It is shown that the results of the microscopic theory at least qualitatively agree with both the results obtained for model examples and experimental results obtained recently for adamantane.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Kucherov M. M.
Заглавие : On the effect of an inhomogeneous magnetic field on high-frequency asymptotic behaviors of correlation functions of spin lattices
Место публикации : JETP Letters. - 2018. - Vol. 107, Is. 9. - P.553-557. - ISSN 0021-3640, DOI 10.1134/S002136401809014X. - ISSN 1090-6487(eISSN)
Примечания : Cited References: 39
Предметные рубрики: HEISENBERG PARAMAGNET
SYSTEMS
TIME
RELAXATION
DYNAMICS
SPECTRA
Аннотация: Singular points of spin autocorrelation functions on the imaginary time axis, which determine the arguments of exponential high-frequency asymptotic behaviors, have been analyzed. It has been shown that randomly distributed inhomogeneous magnetic fields expand the wings of spectra of autocorrelation functions and, thereby, intensify the heating of a system subjected to variable magnetic fields, which are used to create effective Hamiltonians or at the saturation of inhomogeneously broadened EPR lines.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zobov V. E., Lundin A. A.
Заглавие : Decay of multispin multiquantum coherent states in the NMR of a solid
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 112, Is. 3. - P451-459. - ISSN 1063-7761, DOI 10.1134/S1063776111020129
Примечания : Cited References: 24
Предметные рубрики: SYSTEMS
SPECTRA
Ключевые слова (''Своб.индексиров.''): adiabatic approximations--andersons--coherent state--dynamic phenomena--experimental data--local fields--model-based--radiospectroscopy--relaxation functions--spin precession--theoretical result--two-component--coherent light
Аннотация: A model based on the Anderson adiabatic approximation, which is widely used for describing various aspects of dynamic phenomena in conventional radiospectroscopy, is proposed for describing the decay of multispin multiquantum coherent states in a solid. The coherent state relaxation function is represented by the product of two functions corresponding to spin precession in a two-component local field with a correlated and an uncorrelated component. Theoretical results of this study explain the experimental data reported in a number of publications and are in good agreement with these data.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shi, Xin, Wu, Yong, Wang, Jian Guo, Kimberg V., Zhang, Song Bin
Заглавие : X-ray transient absorption spectroscopy by an ultrashort x-ray-laser pulse in a continuous-wave IR field
Место публикации : Phys. Rev. A. - 2020. - Vol. 101, Is. 2. - Ст.023401. - ISSN 2469-9926, DOI 10.1103/PhysRevA.101.023401. - ISSN 2469-9934(eISSN)
Примечания : Cited References: 56. - Grants from the National Basic Research Program of China (Grant No. 2017YFA0403200), National Natural Science Foundation of China (Grants No. 11604197, No. 11934004, and No. 11974230), the Science Challenge Program of China (Grants No. TZ2018005 and No. TZ2016005), and the Organization Department of CCCPC are acknowledged. V.K. acknowledges financial support from Swedish Research Council within the State Contract of the Ministry of Education and Science of the Russian Federation for Siberian Federal University for Scientific Research in 2017-2019 (Project No. 3.2662.2017)
Предметные рубрики: MOLECULAR NITROGEN
TIME
DYNAMICS
PHASE
SPECTRA
DECAY
Аннотация: X-ray transient absorption spectra (XTAS) of molecules are theoretically investigated in a femtosecond x-ray pump and continuous-wave (cw) infrared (IR)-control scenario. The scheme is exemplified by a CO molecule resonantly pumped into carbon and oxygen core-excited 1s→π∗ states by a weak femtosecond x-ray pulse, while dynamic Stark shifts are induced by the cw IR-control radiation. As a result, significant shoulder structures appear in XTAS showing strong dependence on the phase of IR radiation relative to the envelope of the x-ray pulse. Due to a significant difference in the frequencies of the two pulses, the present XTAS scheme provides much clear interpretation of the dynamic Stark effects as compared to the attosecond UV transient absorption scenario. Within the suggested two-level model, where the total spectrum is decomposed as incoherent superposition of contributions from different vibrational excitations weighted by the Franck-Condon Factors, all spectral structures can be well identified and interpreted in a good agreement with the full-scale molecular simulations. Well-characterized XTAS in the proposed IR-control scheme can be applied for fine phase synchronization between IR and x-ray pulses, highly demanded in modern experiments on x-ray free-electron lasers.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Edelman I. S., Greben'kova Yu. E., Sokolov A. E., Molokeev M. S., Aleksandrovsky A. S., Chichkov V. I., Andreev N. V., Mukovskii Y.
Заглавие : Visible magnetic circular dichroism spectroscopy of the Pr0.8Sr0.2MnO3 and Pr0.6Sr0.4MnO3 thin films
Место публикации : AIP Adv.: American Institute of Physics, 2014. - Vol. 4, Is. 5. - Ст.057125. - ISSN 2158-3226, DOI 10.1063/1.4879818
Примечания : Cited References: 30. - The work was supported partly by the Russian Foundation for Basic Researches, grant No’s 14-02-01211, 12-02-00717-a and Grant of the Russian President No Sh-2886.2014.2
Предметные рубрики: MANGANITES
LA1-XSRXMNO3
PEROVSKITES
SPECTRA
Аннотация: Visiblemagnetic circular dichroism (MCD) in Pr1-xSrxMnO3 with x=0.2 and 0.4was investigated for the first time. Samples for the investigation – polycrystalline films with thickness from 20 to 150 nm were prepared with the dc magnetron sputtering. MCD spectra obtained in the energy interval 1–4 eV at temperatures 100–300 K consist of several maxima with different intensities: very strong one near 3.25–3.4 eV and a broad essentially weaker band near 2 eV. An additional maximum of opposite sign arises in the samples with x = 0.4MCD spectrum at 2.33 eV. Experimental spectra were decomposed to several Gaussian components, and their amplitudes temperature dependences were analyzed. In the case of x = 0.2, all four Gaussian components are characterized by the identical temperature dependence of their amplitudes. In the case of x = 0.4, maxima observed in different spectral intervals demonstrate different temperature dependences of their amplitudes. One more unexpected phenomenon is associated with the different MCD value change in different spectral intervals when coming from x = 0.2 to x = 0.4: high-energy maximum increases more than twice while low-energy maxima intensity stays at that, practically, unchanged.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kazak N. V., Bayukov O. A., Ovchinnikov S. G., Vasiliev A. D., Rudenko V. V., Ivanova N. B., Knyazev Yu. V., Bartolom J., Arauzo A.
Заглавие : The superexchange interactions in mixed Co-Fe ludwigite
Место публикации : J. Magn. Magn. Mater. - 2011. - Vol. 323, Is. 5. - P.521-527. - MAR. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2010.09.057
Примечания : Cited Reference Count: 15. - Гранты: This study was supported by the Russian Foundation for Basic Research (Project no. 09-02-00171-a), the Federal Agency for Science and Innovation (Rosnauka) (Project no. MK-5632. 2010.2), Physical Division of the Russian Academy of Science, the program "Strongly Correlated Electrons", project 2.3.1.; The financial support of Spanish MINCYT, MAT08/1077 and Aragonese E-34 project are also acknowledged.Финансирующая организация: Russian Foundation for Basic Research [09-02-00171-a]; Federal Agency for Science and Innovation (Rosnauka) [MK-5632. 2010.2]; Physical Division of the Russian Academy of Science; "Strongly Correlated Electrons" [2.3.1]; Spanish MINCYT [MAT08/1077]; Aragonese E-34 project
Предметные рубрики: TRANSPORT-PROPERTIES
SPECTRA
Ключевые слова (''Своб.индексиров.''): ludwigite structure--magnetic susceptibility--magnetic frustration--mott conductivity--ludwigite structure--magnetic frustration--magnetic susceptibility--mott conductivity--ac susceptibility--cation distributions--crystal data--crystallographic sites--electrical resistivity--iron atoms--low temperatures--ludwigite structure--magnetic behavior--magnetic frustrations--magnetic system--magnetic transitions--mossbauer--mossbauer effects--mott conductivity--mott hopping--superexchange energy--superexchange interaction--temperature regions--trivalent iron--variable range--cobalt--electric conductivity--magnetic susceptibility--magnetism--mossbauer spectroscopy--x ray diffraction--crystal structure
Аннотация: The crystal structure, cation distribution and exchange interactions in the Co2.25Fe0.75O2BO3 ludwigite have been explored through X-ray diffraction, electrical resistivity, ac-susceptibility and Mossbauer effect measurements. The crystal data have shown that iron atoms occupy the most symmetric crystallographic sites Fe4 and Fe2. The complex magnetic behavior with two magnetic transitions near 70 and 115 K at low temperatures was found. The Mossbauer data have displayed the trivalent iron states only. The values of superexchange energies have been estimated for Co3O2BO3 and Co2.25Fe0.75O2BO3 yielding a significant role of frustrations in the ludwigite magnetic system. Variable range Mott hopping conductivity law was proved to be valid in the wide temperature region, pointing out a localized character of charge carriers rather than collective. (C) 2010 Elsevier B.V. All rights reserved.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavriliuk A. G., Trojan I. A., Ovchinnikov S. G., Lyubutin I. S., Sarkisyan V. A.
Заглавие : The mechanism of suppression of strong electron correlations in FeBO3 at high pressures
Разночтения заглавия :авие SCOPUS: The mechanism of suppression of strong electron correlations in FeBO 3 at high pressures
Место публикации : J. Exp. Theor. Phys.: AMER INST PHYSICS, 2004. - Vol. 99, Is. 3. - P566-573. - ISSN 1063-7761, DOI 10.1134/1.1809686
Примечания : Cited References: 18
Предметные рубрики: MAGNETIC COLLAPSE
TRANSITION
SPECTRA
ABSORPTION
STATE
Ключевые слова (''Своб.индексиров.''): crystal structure--high pressure effects--light absorption--parameter estimation--phase transitions--spectrum analysis--crystal field--electron correlations--generalized tight binding method--hybridization--iron compounds
Аннотация: The optical absorption spectra of iron borate (FeBO3) are measured at high pressures up to P = 82 GPa. A mechanism of suppression of strong electron correlations is proposed within the framework of the generalized tight binding method, which leads to the experimentally observed magnetic, electronic, and structural phase transitions. Taking into account peculiarities of the crystal structure of FeBO3 and the strong s-p hybridization of boron and oxygen, it is established that, as the distance between ions varies with increasing pressure, the crystal field parameter begins to play a decisive role in the electron transitions, while the influence of the d band broadening is negligibly small. Parameters of the theory are calculated as functions of the pressure. (C) 2004 MAIK "Nauka / Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Golovnev N. N., Molokeev M. S., Vereshchagin, Sergey N., Sterkhova I. V., Atuchin V. V.
Заглавие : The cis-trans isomer transformation, spectroscopic and thermal properties of Li, Na, K 1,3-diethyl-2-thiobarbiturate complexes
Коллективы : Ministry of Education and Science of the Russian Federation
Место публикации : Polyhedron: PERGAMON-ELSEVIER SCIENCE LTD, 2015. - Vol. 85. - P.493-498. - ISSN 0277-5387, DOI 10.1016/j.poly.2014.09.011
Примечания : Cited References:42. - The study has been carried out within the public task of the Ministry ofEducation and Science of the Russian Federation for research engineeringat the Siberian Federal University in 2014. V.V.A. is partly supportedby the Ministry of Education and Science of the Russian Federation.
Предметные рубрики: CRYSTAL-STRUCTURE
2-THIOBARBITURIC ACID
STRUCTURAL-CHARACTERIZATION
HYDROGEN-BOND
DIFFRACTION
THIOBARBITURATE
CHEMISTRY
NETWORKS
SPECTRA
SERIES
Ключевые слова (''Своб.индексиров.''): 1,3-diethyl-2-thiobarbituric acid--alkali ions--x-ray diffraction--infrared spectroscopy--thermal analysis
Аннотация: Three new complexes of 1,3-diethyl-2-thiobarbituric acid (C8H11N2O2S, HDETBA) with Li+, Na+, K+ alkali ions were synthesized. The complexes have been prepared by neutralization of 1,3-diethyl-2-thiobarbituric acid with the corresponding metal hydroxide in aqueous solution. The colorless crystals have been investigated using X-ray single crystal and powder techniques and characterized by differential scanning calorimetry, thermogravimetry and infrared spectroscopy. The compounds of MDETBA with M = Li and M = Na crystallize in the monoclinic lattice with a = 10.678(1) Å, b = 7.2687(9) Å, c = 13.202(2) Å, β = 108.841(2)°, Z = 4, V = 969.8(2) Å3, S.G. P21/n and a = 10.534(2) Å, b = 7.604(1) Å, c = 14.186(1) Å, β = 108.964(4)°, Z = 4, V = 1074.6(3) Å3, S.G. P21/n, respectively. Сompound KDETBA crystallizes in the orthorhombic lattice with a = 4.2541(6) Å, b = 14.739(2) Å, c = 16.635(3) Å, Z = 4, V = 1043.1(3) Å3, S.G. P212121. In Li(I) and Na(I) complexes, the DETBA− ion is in cis-configuration and, in the K(I) complex, this ion is in trans-configuration. The reason for the transformation from cis- to trans-configuration has been rationalized.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Vasiliev A. D., Zel'bst E. A., Soldatenko A. S., Bolgova Yu.I., Trofimova O. M., Voronkov M. G.
Заглавие : Synthesis and molecular structure of cobalt(II) complex with 1-(1-silatranylmethyl)-1,2,4-triazole
Место публикации : Struct. Chem.: Springer/Plenum Publishers, 2013. - Vol. 24, Is. 4. - P.1001-1005. - ISSN 1040-0400, DOI 10.1007/s11224-012-0121-0
Примечания : Cited References: 24
Предметные рубрики: REACTIVITY
DERIVATIVES
CRYSTAL
SPECTRA
Ключевые слова (''Своб.индексиров.''): complexes--1-(1-silatranylmethyl)-1,2,4-triazole--cobalt dichloride--x-ray diffraction
Аннотация: Reaction of cobalt chloride with 1-(1-silatranylmethyl)-1,2,4-triazole in benzene afforded complex CoCl2 center dot 2L (L = 1-(1-silatranylmethyl)-1,2,4-triazole). It was isolated as the solvate [CoCl2 center dot 2L]center dot CH2Cl2 (1) by recrystallization from dichloromethane and structurally characterized by single-crystal X-ray diffraction. It crystallizes in the monoclinic space group P2(1)/m with a = 6.798(2) E, b = 20.326(5) E, c = 11.005(3) E, and Z = 4. The cobalt atom is in slightly distorted square-planar environment, coordinated to two nitrogen atoms from two ligands and two chloride ions.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Lyubutin I. S., Korotkov, N. Yu., Frolov K. V., Kazak N. V., Platunov M. S., Knyazev, Yu. V., Bezmaternykh L. N., Ovchinnikov S. G., Arauzo A., Bartolome J.
Заглавие : Spin-glass behavior of warwickite MgFeBO4 and CoFeBO4 crystals observed by Mössbauer spectroscopy
Место публикации : J. Alloys Compd.: Elsevier Science, 2015. - Vol. 642. - P.204-209. - ISSN 0925, DOI 10.1016/j.jallcom.2015.04.067. - ISSN 18734669(eISSN)
Примечания : Cited References:29. - This study was supported by the Russian Foundation for Basic Research (Grants # 14-02-00483a, 14-02-31051-mol-a, 13-02-00958- a, and 13-02-00358-a), by the Council for Grants of the President of the Russian Federation (Project Nos. NSh-2886.2014.2 and SP-938.2015.5), by the Grant of KSAI, Krasnoyarsk regional fund of supporting scientific and technological activities and by the program of Foundation for Promotion of Small Enterprises in Science and Technology (''UMNIK'' program). The Spanish MINECO project MAT2011/23791, MAT2014/53921 and DGA E-34 are acknowledged.
Предметные рубрики: SOLVABLE MODEL
SPECTRA
Ключевые слова (''Своб.индексиров.''): warwickites--spin-glass--mossbauer spectroscopy
Аннотация: Single crystals of MgFeBO4 and СоFeBO4 warwickites were obtained. The effects of charge ordering and magnetic properties were investigated by Mössbauer spectroscopy. Cation distribution over M1 and M2 nonequivalent sites and the average charge at the metal positions were established. Low temperature Mössbauer spectra reveal spin-glass behavior, with spin-freezing temperatures TSG of 15.2 and 33.2 K for Mg- and Co-warwickites, respectively, higher than that observed from the d.c. and a.c. magnetic susceptibility measurements. The difference is explained in terms of dynamical scaling theory. The specific shape of the Mössbauer spectra in the vicinity of the magnetic transition at TSG shows the difference between spin-glass and superparamagnetic behavior and demonstrates an overwhelming role of the exchange anisotropy in the properties of Mg-warwickite. In Co-warwickite the increase of magnetocrystalline anisotropy provokes an increase in magnetic viscosity.Были получены монокристаллы MgFeBO4 и CoFeBO4 warwickites. Эффекты упорядочения зарядов и магнитные свойства были исследованы методом мессбауэровской спектроскопии. Было определено распределение катионов на М1 и M2 неэквивалентных позициях и средний заряд на металлических позициях. При низкой температуре Мессбауэровские спектры показывают поведение типа спинового стекла, с температурой замораживания спинов TSG 15.2 и 33.2 K для MG-и Co-warwickites, соответственно, более высокие, чем наблюдалось от постоянного тока и на ~ измерениях магнитной восприимчивости. Разница объясняется в терминах динамической теории подобия. Удельный форма спектров Мессбауэра в непосредственной близости от магнитного перехода на TSG показывает разницу между спин-стекольным и суперпарамагнитным поведением и демонстрирует подавляющее роль обменной анизотропии в свойствах Mg-warwickite. В Co-warwickite увеличение магнитокристаллической анизотропия провоцирует увеличение магнитной вязкости.
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