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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S.
Заглавие : Quantum spin liquid in an antiferromagnet with four-spin interactions
Место публикации : Phys. Solid State: AMER INST PHYSICS, 1997. - Vol. 39, Is. 8. - P1246-1250. - ISSN 1063-7834, DOI 10.1134/1.1130054
Примечания : Cited References: 14
Предметные рубрики: MONTE-CARLO
LA2CUO4
STATE
Аннотация: A quantum Monte Carlo study of the anisotropic antiferromagnet with four-spin interaction (K) and with spin S= 1/2 on a square lattice is reported. Temperature dependences of the capacity, susceptibility, spin correlation functions, and correlation length, and field dependences of magnetization are calculated. Phase diagrams of the ground-state antiferromagnet and gap (K0) and gapless (K0) quantum spin liquids are determined in the exchange-anisotropy-four-spin-coupling-constant (K), magnetic-field (H)-temperature (T), and temperature- (T)-K planes for an exchange anisotropy of 0.1 J. (C) 1997 American Institute of Physics.
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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) : Alekseev K. N., Berman G. P., Campbell D. K.
Заглавие : Strange attractor in resonant tunneling
Место публикации : Phys. Rev. B: AMERICAN PHYSICAL SOC, 1998. - Vol. 58, Is. 7. - P3954-3962. - ISSN 0163-1829, DOI 10.1103/PhysRevB.58.3954
Примечания : Cited References: 38
Предметные рубрики: INTRINSIC BISTABILITY
RING CAVITY
OPTICAL TURBULENCE
TRANSMITTED LIGHT
QUANTUM-WELLS
OSCILLATIONS
BARRIERS
SYSTEM
STATE
TIME
Аннотация: We consider the process of resonant electron tunneling through a double-barrier potential, taking into account nonlinear dynamical effects generated by charge accumulation in the interbarrier space. We use the perturbation approach of Davydov and Ermakov, which was developed for investigating intrinsic bistability in resonant tunneling. For incoming electron flow, which is modulated slowly in time, we show that the resulting nonlinear dynamics can become chaotic, with the chaos described (because of the open nature of the system) by a strange attractor. We determine the conditions for the existence of this strange attractor and estimate characteristic experimental parameters for its observation.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S.
Заглавие : A study of anisotropic Heisenberg antiferromagnet with S=1/2 on a square lattice by Monte-Carlo method
Место публикации : Phys. Status Solidi B. - 1998. - Vol. 207, Is. 2. - P.491-498. - ISSN 0370-1972, DOI 10.1002/(SICI)1521-3951(199806)207:2491::AID-PSSB4913.0.CO;2-G
Примечания : Cited References: 24
Предметные рубрики: EU2CUO4
LA2CUO4
ORDER
MODEL
STATE
Аннотация: The two-dimensional (2D) Heisenberg model (J 0) with anisotropic exchange Delta = 1-J(X)/J(Z) greater than or equal to 0 and with S = 1/2 is studied by the quantum Monte-Carlo method. Energy, susceptibility, specific heat, spin-spin correlation functions, and correlation radius are calculated. The dependence of the Neel temperature T(N)/J = 2/ln(11/Delta) on the exchange anisotropy is determined. The static magnetic factor is very slowly decreased for T/J 0.4. It is assumed to realize topological excitations in the range of these temperatures. The correlation radius of the isotropic Heisenberg model is fitted by the dependence 1/xi = 2.05T(1.0(6))/exp (1.0(4)/T).The temperature behavior of the static structural magnetic factor in La(2)CuO(4) and Er(2)CuO(4) for T T(N) is in agreement with the MC calculations.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Lyubutin I. S., Gavriliuk A. G., Struzhkin V. V., Ovchinnikov S. G., Kharlamova S. A., Bezmaternykh L. N., Hu M., Chow P.
Заглавие : Pressure-induced electron spin transition in the paramagnetic phase of the GdFe3(BO3)(4) Heisenberg magnet
Разночтения заглавия :авие SCOPUS: Pressure-induced electron spin transition in the paramagnetic phase of the GdFe3(BO3)4 Heisenberg magnet
Место публикации : JETP Letters. - 2006. - Vol. 84, Is. 9. - P.518-523. - ISSN 0021-3640, DOI 10.1134/S0021364006210119
Примечания : Cited References: 26
Предметные рубрики: TRIGONAL GDFE3(BO3)(4)
NUCLEAR
FEBO3
STATE
SCATTERING
COLLAPSE
Аннотация: The HS - LS spin crossover effect (high-spin - low-spin transition) induced by high pressure in the range 45-53 GPa is observed in trivalent Fe3+ ions in the paramagnetic phase of a (GdFe3)-Fe-57(BO3)(4) gadolinium iron borate crystal. This effect is studied in high-pressure diamond-anvil cells by two experimental methods using synchrotron radiation: nuclear resonant forward scattering (NFS) and Fe K-beta high-resolution x-ray emission spectroscopy (YES). The manifestation of the crossover in the paramagnetic phase, which has no order parameter to distinguish between the HS and LS states, correlates with the optical-gap jump and with the insulator-semiconductor transition in the crystal. Based on a theoretical many-electron model, an explanation of this effect at high pressures is proposed.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kolovsky A. R.
Заглавие : Condition of correspondence between quantum and classical dynamics for a chaotic system
Место публикации : Phys. Rev. Lett.: AMER PHYSICAL SOC, 1996. - Vol. 76, Is. 3. - P340-343. - ISSN 0031-9007, DOI 10.1103/PhysRevLett.76.340
Примечания : Cited References: 18
Предметные рубрики: STANDARD MAP
STATE
Аннотация: The paper deals with the dynamics of a semiclassical system under the influence of the environment. The effect of the environment is shown to convert the quantum dynamics of the system into the classical one. The condition of correspondence between quantum and classical dynamics is obtained and checked numerically.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gladczuk L., Szymczak R., Nabialck A., Krynetskii I., Petrakovskii G. A., Sablina K. A., Vorotynov A. M., Szymczak H.
Заглавие : Giant magnetostriction of CuGeO3
Коллективы : International Conference on Low Temperature Physics
Место публикации : Czech. J. Phys. - 1996. - Vol. 46. - P.1969-1970. - ISSN 0011-4626, DOI 10.1007/BF02570976
Примечания : Cited References: 10
Предметные рубрики: SPIN-PEIERLS TRANSITION
COMPOUND CUGEO3
SYSTEM CUGEO3
STATE
Аннотация: The magnetostriction of CuGcO(3) single crystals has been measured in the temperature range from 5 to 16 K in magnetic fields up to 12 T. Giant values of the magnetostrictive strains along the b-axis is observed near the phase transition from the dimerized phase to the high field magnetic phase. The field induced magnetostriction in the antiferromagnetic phase is considerably smaller than in the dimerized phase.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Volkov N. V., Petrakovskii G. A., Patrin K. G., Sablina K. A., Eremin E. V., Vasiliev V., Vasiliev A., Molokeev M. S., Boni P., Clementyev E.
Заглавие : Intrinsic inhomogeneity in a (La0.4Eu0.6)(0.7)Pb0.3MnO3 single crystal: Magnetization, transport, and electron magnetic resonance studies
Разночтения заглавия :авие SCOPUS: Intrinsic inhomogeneity in a (La0.4 Eu0.6) 0.7 Pb0.3 MnO3 single crystal: Magnetization, transport, and electron magnetic resonance studies
Место публикации : Phys. Rev. B: AMERICAN PHYSICAL SOC, 2006. - Vol. 73, Is. 10. - Ст.104401. - ISSN 1098-0121, DOI 10.1103/PhysRevB.73.104401
Примечания : Cited References: 29
Предметные рубрики: INSULATOR-METAL TRANSITION
PHASE-SEPARATION
MAGNETORESISTANCE
MANGANITES
EXCHANGE
STATE
Аннотация: Conventional magnetic and transport measurements of the melt-grown mixed-valence manganite (La0.4Eu0.6)(0.7)Pb0.3MnO3 have been supplemented by a magnetic resonance study. The experimental data support the model of two magnetic phases coexisting in the crystal volume. At a temperature T-*, which is well above Curie temperature T-C, ferromagnetic clusters appear in the sample. These ferromagnetic regions possess a higher conductivity in comparison with the paramagnetic background (majority phase). On cooling through T-C, the magnetization of the spatially confined ferromagnetic clusters of the minority phase freezes in random directions with respect to the magnetization of the ferromagnetic majority phase due to the difference of the exchange interactions at the phase boundaries from the intraphase interactions in sign and value. Such a mixed state is responsible for the observed magnetic glassylike behavior of the system that is characteristic of inhomogeneous magnets. The fluctuations of the magnetic coupling value and sign in the sample volume are related to strong competition between the ferromagnetic and antiferromagnetic exchange interactions, which, in turn, results from the quenched disorder caused by the random chemical replacement of the perovskite A site of the manganite. A phase-separation state comprised of two different ferromagnetic phases has been used to account for the colossal magnetoresistance phenomenon and the magnetic-field-driven nonlinear conduction found in the crystal.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Patrin G. S., PETRAKOVSKII G. A., KHARITONOV I. E.
Заглавие : Detection of magneto-dependent higher harmonics in htsc ceramics via the change of the low field microwave response under the passing of an alternating-current
Место публикации : Phys. Lett. A. - 1991. - Vol. 158, Is. 3-4. - P.167-170. - ISSN 0375-9601, DOI 10.1016/0375-9601(91)90921-T
Примечания : Cited References: 15
Предметные рубрики: BA-CU-O
GENERATION
STATE
Аннотация: The results of an investigation on the generation of higher harmonics under the passing of a low frequency current in HTSC ceramics by microwave spectroscopy methods are presented. It is found that the generation of only even harmonics occurs. The dependence of the signal upon the harmonic number and. as an example for the second harmonic, the temperature dependences of the microwave response parameters are discussed.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Iskhakov R. S., Komogortsev S. V., Balaev A. D., Okotrub A. V., Kudashov A. G., Kuznetsov V. L., Butenko Y. V.
Заглавие : Fe nanowires in carbon nanotubes as an example of a one-dimensional system of exchange-coupled ferromagnetic nanoparticles
Место публикации : JETP Letters. - 2003. - Vol. 78, Is. 4. - P.236-240. - ISSN 0021-3640, DOI 10.1134/1.1622038
Примечания : Cited References: 38
Предметные рубрики: MAGNETIC-PROPERTIES
RANDOM ANISOTROPY
ELECTRODEPOSITED NANOWIRES
NI NANOWIRES
ARRAYS
NANOCRYSTALLINE
ALUMINA
NICKEL
PORES
STATE
Аннотация: The cooperative phenomena revealed in the field and temperature dependences of the magnetization in a system of iron nanoparticles in carbon nanotubes were studied experimentally. The character of the temperature dependences of the magnetization indicates that the ferromagnetic Fe particles in carbon nanotubes are exchange-coupled. In the region where the magnetization approaches saturation, the magnetization curves reveal the power dependence DeltaM similar to H-3/2 typical for a one-dimensional system of exchange-coupled ferromagnetic nanoparticles. (C) 2003 MAIK "Nauka / Interperiodica".
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G.
Заглавие : Many-electron model of band structure and metal-insulator transition under pressure in FeBO3
Место публикации : JETP Letters. - 2003. - Vol. 77, Is. 12. - P.676-679. - ISSN 0021-3640, DOI 10.1134/1.1604419
Примечания : Cited References: 20
Предметные рубрики: PHASE-TRANSITION
FERROMAGNETISM
STATE
Аннотация: A many-electron model is proposed for the band structure of FeBO3 with regard to strong electron correlations in the d (4), d (5), and d (6) configurations. Under normal conditions, FeBO3 is characterized by a dielectric charge-transfer gap in the strong correlation regime U W. With increasing pressure, not only does the d-band W width grow but simultaneously the effective Hubbard parameter U-eff sharply drops, which is due to the crossover of high-spin and low-spin ground state terms of the Fe2+, Fe3+, and Fe4+ ions. It is predicted that a transition from the semiconducting antiferromagnetic state to the metallic paramagnetic state will occur in the high-pressure phase with increasing temperature. (C) 2003 MAIK "Nauka / Interperiodica".
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12.

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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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Starikov A. A., Yakimenko I. I., Berggren K. F.
Заглавие : Scenario for the 0.7-conductance anomaly in quantum point contacts
Место публикации : Phys. Rev. B: AMERICAN PHYSICAL SOC, 2003. - Vol. 67, Is. 23. - Ст.235319. - ISSN 1098-0121, DOI 10.1103/PhysRevB.67.235319
Примечания : Cited References: 23
Предметные рубрики: 2-DIMENSIONAL ELECTRON-GAS
SPIN POLARIZATION
CONDUCTANCE
WIRES
STATE
Аннотация: Effects of spontaneous spin polarization in quantum point contacts (QPC's) are investigated for a realistic semiconductor device structure using the Kohn-Sham local spin-density formalism. At maximal polarization in the contact area, there is a bifurcation into ground-state and metastable solutions. The conduction associated with the metastability is lower than for the normal state. With increasing temperature, the conductance should therefore show an anomalous behavior as observed. For the present device we do not recover resonance or quasibound states.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shaikhutdinov K. A., Balaev D. A., Popkov S. I., Petrov M. I.
Заглавие : Transport and magnetic properties of Y3/4Lu1/4Ba2Cu3O7+Y3Fe5O12 composites representing a Josephson-type superconductor-ferrimagnet-superconductor weak-link network
Разночтения заглавия :авие SCOPUS: Transport and Magnetic Properties of Y3/4Lu1/4Ba 2Cu3O7 + Y3Fe5O 12 Composites Representing a Josephson-Type Superconductor-Ferrimagnet-Superconductor Weak-Link Network
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2003. - Vol. 45, Is. 10. - P1866-1873. - ISSN 1063-7834, DOI 10.1134/1.1620087
Примечания : Cited References: 36
Предметные рубрики: RESISTIVE PROPERTIES
JUNCTION NETWORK
SYSTEM
TRANSITION
CURRENTS
VOLTAGE
STATE
FIELD
Аннотация: Y3/4Lu1/4Ba2Cu3O7 + Y3Fe5O12 composites with different volume ratios of the starting components were synthesized. The composites model an S-F-S Josephson junction network, where S stands for a superconductor and F, for a ferrimagnet. A study of the transport characteristics of the composites revealed that the temperature behavior of the electrical resistivity rho(T) below the superconducting transition point T-C is different in two regions separated by a temperature T-m. Below T-m, the current-voltage characteristics of the composites are nonlinear, while in the interval from T-C to T-m the values of rho(T) do not depend on the transport current j and magnetic field H. This behavior of rho(T, j ) and rho(T, H) is assigned to specific features of the tunneling of superconducting carriers through the ferrimagnetic layers separating HTSC grains in the composite. Magnetic measurements showed the diamagnetic response of HTSC grains to be lower in composites with a ferrimagnet. (C) 2003 MAIK "Nauka / Interperiodica".
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Petrakovskii G. A., Balaev A. D., Vorotynov A. M.
Заглавие : Magnetic susceptibility and magnetic-field behavior of CuB(2)O(4) copper metaborate
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2000. - Vol. 42, Is. 2. - P321-325. - ISSN 1063-7834, DOI 10.1134/1.1131205
Примечания : Cited References: 10
Предметные рубрики: TRANSITION
STATE
Аннотация: An experimental study is reported regarding the temperature dependence of the magnetic susceptibility of a CuB(2)O(4) tetragonal single crystal within the 4.2-200-K range. It has been established that the magnetic susceptibility exhibits anomalies at 21 and 10 K and depends strongly on crystal orientation in the magnetic field. A study has been carried out of the field dependences of the magnetization of CuB(2)O(4) at various temperatures and crystal orientations. It is shown that for T 21 K, the crystal is in a paramagnetic state determined by Cu(2+) copper ions with an effective magnetic moment of 1.77 mu(B). Within the 10-21 K interval, the field dependence of the magnetization is typical of a weak ferromagnet with magnetic moments of the two antiferromagnetically coupled sublattices lying in the tetragonal plane of the crystal. The spontaneous weakly-ferromagnetic moment is 0.56 emu/g at 10 K. The canting angle of the sublattice magnetic moments, determined by the Dzyaloshinski-Moriya interaction, is 0.49 degrees. It is believed that below 10 K, the CuB(2)O(4) crystal retains its easy-plane magnetic structure, but with a zero spontaneous magnetic moment. (C) 2000 MAIK "Nauka/Interperiodica".
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bayukov O. A., Petrakovskii G. A., Savitskii A. F.
Заглавие : Orbital ordering in CuGeO3
Место публикации : Phys. Solid State: AMER INST PHYSICS, 1998. - Vol. 40, Is. 9. - P1534-1539. - ISSN 1063-7834, DOI 10.1134/1.1130602
Примечания : Cited References: 25
Предметные рубрики: SPIN-PEIERLS TRANSITION
COMPOUND CUGEO3
DIMERIZATION
STATE
SUSCEPTIBILITY
(VO)2P2O7
LADDER
Аннотация: The combined effect of the ligand crystal field and the exchange interaction on the Cu2+ cation in CuGeO3 is examined. It is shown that, if the magnitude of the exchange interaction exceeds the splitting of the energy levels of the d(x2-y2) and d(xy) orbitals, then an alternate filling of the d orbitals along a chain (orbital ordering) is possible. This effect creates an antiferromagnetic interaction between Cu2+ pairs in 90 degrees exchange and a doubling of the lattice period. A Jahn-Teller pseudoeffect causes singletization of the ground state of the antiferromagnetic chain of Cu2+ spins. (C) 1998 American Institute of Physics. [S1063-7834(98)02609-4].
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Petrakovskii G. A., Pankrats A. I., Popov M. A., Balaev A. D., Velikanov D. A., Vorotynov A. M., Sablina K. A., Roessli B., Schefer J., Amato A., Staub U., Boehm M., Ouladdiaf B.
Заглавие : Magnetic properties of copper metaborate CuB2O4
Место публикации : Low Temp. Phys. - 2002. - Vol. 28, Is. 8-9. - P.606-612. - ISSN 1063-777X, DOI 10.1063/1.1511704; \b Физика низких температур
Примечания : Cited References: 17
Предметные рубрики: SINGLE-CRYSTALS
RESONANCE
STATE
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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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pankrats A. I., Petrakovskii G. A., Volkov N. V.
Заглавие : Antiferromagnetic resonance in CuB2O4 single crystal
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2000. - Vol. 42, Is. 1. - P96-102. - ISSN 1063-7834, DOI 10.1134/1.1131174
Примечания : Cited References: 20
Предметные рубрики: STATE
Аннотация: The frequency-field, temperature, and angular dependences of the antiferromagnetic resonance parameters for the tetragonal CuB2O4 single crystal are studied in the frequency range 2.6-80 GHz and at temperatures of 4.2-30 K. The results obtained confirm the fact that, in the high-temperature state in the range 10-21 K, this compound is an easy-plane weak ferromagnet. The temperature dependence of the Dzyaloshinski field is determined. An abrupt change observed in the frequency-field dependence of the magnetic resonance at T = 4.2 K and H perpendicular to C-4 indicates the transition to the weak ferromagnetic state induced by the external field H-perpendicular to. The phase diagram for CuB2O4 is constructed on the H-perpendicular to-T coordinates. It is demonstrated that, in the low-temperature state, the magnetic moments of copper ions remain in the basal plane, but the weak ferromagnetism is absent. (C) 2000 MAIK "Nauka/Interperiodica".
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Golovnev N. N., Molokeev M. S., Sterkhova I. V., Lesnikov M. K.
Заглавие : Structure of Barbituratobis(2,2'-Dipyridyl)copper(II) Heptahydrate
Коллективы : Ministry of Education and Science of the Russian Federation [4.7666.2017/BCh]
Место публикации : Russ. J. Coord. Chem. - 2019. - Vol. 45, Is. 8. - P.569-572. - ISSN 1070-3284, DOI 10.1134/S1070328419080037. - ISSN 1608-3318(eISSN)
Примечания : Cited References: 25. - This work was supported by the Ministry of Education and Science of the Russian Federation in the framework of the state task for the Siberian Federal University for 2017-2019 (4.7666.2017/BCh).
Предметные рубрики: IONIC CO-CRYSTALS
BARBITURIC-ACID
COMPLEXES
STATE
Аннотация: The structure of the complex [Cu(Bipy)2(BA)] ∙ 7H2O (I), where Bipy is 2,2'-dipyridyl, and BA2– is the barbituric acid anion (H2BA), is determined (CIF file CCDC no. 1887338). The thermal decomposition and IR spectrum of complex I are studied. The crystals are orthorhombic: a = 26.118(3), b = 27.685(3), c = 15.683(2) Å, V = 11 370(2) Å3, space group Fdd2, Z = 16. The discrete structure of the polar crystal consists of neutral [Cu(Bipy)2(BA)] particles and molecules of crystallisation water . The Cu2+ ion is bound to the N atoms of two bidentate Bipy molecules and the N atom of the BA2− ion at the vertices of the trigonal bipyramid CuN5. Compound I is the first example of the metal complex only with the N-coordinated anions of barbituric acid (BA2−, НBA−). The structure is stabilized by hydrogen bonds O−H∙∙∙O and N−H∙∙∙O to form a three-dimensional network with the π–π interaction between the Bipy molecules. The compound begins to lose water at ~50°С and is completely dehydrated above 200°С.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kuz'min V. I., Orlov Yu. S., Zarubin A. E., Ovchinnikova T. M., Ovchinnikov S. G.
Заглавие : Magnetism in spin crossover systems: Short-range order and effects beyond the Heisenberg model
Коллективы : Russian Scientific FoundationRussian Science Foundation (RSF) [18-12-00022]
Место публикации : Phys. Rev. B. - 2019. - Vol. 100, Is. 14. - Ст.144429. - ISSN 2469-9950, DOI 10.1103/PhysRevB.100.144429. - ISSN 2469-9969(eISSN)
Примечания : Cited References: 72. - The authors thank the Russian Scientific Foundation for the financial support under Grant No. 18-12-00022.
Предметные рубрики: LOWER-MANTLE
STATE
TRANSITION
PRESSURE
IRON
SUSCEPTIBILITY
Аннотация: To study non-Heisenberg effects in the vicinity of spin crossover in strongly correlated electron systems we derive an effective low-energy Hamiltonian for the two-band Kanamori model. It contains a Heisenberg high-spin term proportional to exchange constant as well as a low-spin term proportional to spin gap parameter ɛs. Using cluster mean field theory we obtain several non-Heisenberg effects. Near the critical value of spin gap ɛcs there is a magnetic phase transition of first order. In the vicinity of ɛcs in the paramagnetic phase we observe nontrivial behavior of the Curie constant in the paramagnetic susceptibility in the wide range of temperature. Reentrant temperature behavior of nearest-neighbor spin-spin correlations is observed at ɛsɛcs. Finally, the pressure-temperature magnetic phase diagram for ferroperriclase is obtained using the effective Hamiltonian.
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