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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorev M. V., Flerov I. N., Tressaud A., Denu D., Zaitsev A. I., Fokina V. D.
Заглавие : A study of the phase diagrams of (NH4)(3)Ga1-xScxF6 ammonium cryolites
Разночтения заглавия :авие SCOPUS: A study of the phase diagrams of (NH4)3Ga1-xScxF6 ammonium cryolites
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2002. - Vol. 44, Is. 10. - P1954-1960. - ISSN 1063-7834, DOI 10.1134/1.1514787
Примечания : Cited References: 15
Предметные рубрики: TRANSITIONS
Аннотация: This paper reports on the results of analyzing p-T and x-T phase diagrams and calorimetric properties of solid solutions in (NH4)(3)Ga1 - xScxF6 cryolites with scandium concentrations x = 0.0, 0.1, 0.35, 0.4, 0.6, 0.8, and 1.0. The thermodynamic parameters of the phase transitions observed in the studied compounds are determined. The generalized phase diagram and successive structural transformations in a series of (NH4)(3)Me3+F6 ammonium cryolites are discussed. (C) 2002 MAIK "Nauka/Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Boldyrev K. N., Pisarev R. V., Bezmaternykh L. N., Popova M. N.
Заглавие : Antiferromagnetic dichroism in a complex multisublattice magnetoelectric CuB2O4
Коллективы : Russian Academy of Sciences under the Programs for Basic Research; Russian Federation [MK-3521.2015.2], Russian Foundation for Basic Research [15-32-20613, 15-02-04222], Ministry of Education and Science of the Russian Federation [14.B25.0031.25]
Место публикации : Phys. Rev. Lett.: American Physical Society, 2015. - Vol. 114, Is. 24. - Ст.247210. - ISSN 0031, DOI 10.1103/PhysRevLett.114.247210. - ISSN 10797114(eISSN)
Примечания : Cited References:40. - This study was supported by the Russian Academy of Sciences under the Programs for Basic Research, by the President of the Russian Federation (Grant No. MK-3521.2015.2, K. N. B.), by the Russian Foundation for Basic Research (Grants No. 15-32-20613, K. N. B., and No. 15-02-04222, R. V. P.), and by the Ministry of Education and Science of the Russian Federation (Grant No. 14.B25.0031.25, R. V. P.).
Предметные рубрики: MAGNETIC SOLITON LATTICE
COPPER METABORATE
GYROTROPIC BIREFRINGENCE
SPECTROSCOPY
EXCITATIONS
TRANSITIONS
CRYSTALS
Cr2O3
FIELD
Аннотация: Magnetic control of the crystal chirality was announced by Saito et al. [Phys. Rev. Lett. 101, (2008)] on the ground of experiments in CuB2O4. This claim has raised a sharp dispute in the literature because it seemed to contradict the fundamental symmetry principles. We settle this dispute on the basis of a high-resolution optical spectroscopy study of excitonic transitions in CuB2O4. We find that a large sublattice-sensitive antiferromagnetic linear dichroism (LD) emerges at the Néel temperature TN=21 K and show how it could simulate a “magnetic-field control of the crystal chirality.” We prove that the discovered LD is related microscopically to the magnetic Davydov splitting. This LD is highly sensitive to subtle changes in the spin subsystems, which allowed us to observe a splitting of the phase transition into an incommensurate magnetic phase into two transitions (T∗1=8.5 and T∗2=7.9 K) and to suggest elliptical spiral structures below T∗1, instead of a simple circular helix proposed earlier.О магнитном контроле кристаллической хиральности сообщил Сайто и др. [Phys. Rev. Lett. 101, 117402 (2008)] на основании экспериментов в CuB2O4. Это требование вызвало резкий спор в литературе, потому что это казалось, противоречат основным принципам симметрии. Мы урегулировать этот спор на основе исследования с помощью оптической спектроскопии высокого разрешения экситонных переходов в CuB2O4. Мы считаем, что большой подрешетко-чувствительный антиферромагнитный линейный дихроизм (LD) возникает при температуре Нееля TN= 21 Kи показываем, как это может имитировать "контроль магнитным полем кристаллической хиральности." Мы докажем, что обнаруженный LD связанс микроскопическим магнитным Давыдовским расщеплением. Этот Л.Д. весьма чувствителен к тонким изменениям в спиновых подсистем, которые позволили нам наблюдать расщепление фазового перехода в несоизмеримы магнитная фаза в двух переходов (T*1= 8,5 и Т*2 = 7,9 К) и предположить эллиптическую спиральную структуру ниже T*1, вместо простой круговой спирали предложенный ранее.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Xia, Zhiguo, Ma C., Molokeev M. S., Liu Q., Rickert K., Poeppelmeier K. R.
Заглавие : Chemical unit cosubstitution and tuning of photoluminescence in the Ca2(Al1-xMgx)(Al1-xSi1+x)O7:Eu2+ phosphor
Место публикации : J. Am. Chem. Soc.: American Chemical Society, 2015. - Vol. 137, Is. 39. - P.12494-12497. - ISSN 0002-7863, DOI 10.1021/jacs.5b08315
Примечания : Cited References: 24. - This work was supported by the National Natural Science Foundations of China (Grant Nos. 51572023 and 51272242), Natural Science Foundations of Beijing (2132050), the Program for New Century Excellent Talents in University of Ministry of Education of China (NCET-12-0950), Beijing Nova Program (Z131103000413047), and the Funds of the State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, CAS (RERU2015022). C.M. acknowledges financial support from National Natural Science Foundation of China (Grant No. 11204393), Natural Science Foundation Project of Chongqing (Grant No. CSTC2014JCYJA50034), and National Training Programs of Innovation and Entrepreneurship for Undergraduates (Grant No. 201410617001). K.R. recognizes that this material is based upon work supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE-1324585.
Предметные рубрики: LUMINESCENCE PROPERTIES
TRANSITIONS
IONS
Аннотация: The union of structural and spectroscopic modeling can accelerate the discovery and improvement of phosphor materials if guided by an appropriate principle. Herein, we describe the concept of chemical unit cosubstitution as one such potential design scheme. We corroborate this strategy experimentally and computationally by applying it to the Ca2(Al1-xMgx)(Al1-xSi1+x)O7:Eu2+ solid solution phosphor. The cosubstitution is shown to be restricted to tetrahedral sites, which enables the tuning of luminescent properties. The emission peaks shift from 513 to 538 nm with a decreasing Stokes shift, which has been simulated by a crystal-field model. The correlation between the 5d crystal-field splitting of Eu2+ ions and the local geometry structure of the substituted sites is also revealed. Moreover, an energy decrease of the electron-phonon coupling effect is explained on the basis of the configurational coordinate model. © 2015 American Chemical Society.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Dudnikov V. A., Ovchinnikov S. G., Orlov Yu.S., Kazak N. V., Michel C. R., Patrin G. S., Yurkin G.Yu.
Заглавие : Contribution of Co3+ ions to the high-temperature magnetic and electrical properties of GdCoO3
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2012. - Vol. 114, Is. 5. - P.841-849. - ISSN 1063-7761, DOI 10.1134/S106377611203003X
Примечания : Cited References: 28. - This work was supported by the Ural Branch of the Russian Academy of Sciences and Siberian Branch of the Russian Academy of Sciences (project no. 40), the Russian Foundation for Basic Research (project nos. 09-02-00171-a, 10-02-00251), program 2.3 of the Department of Physical Sciences of Russian Academy of Sciences, and Nonprofit Dinastiya Foundation.
Предметные рубрики: SPIN-STATE
RCOO3 R
TRANSITIONS
COBALTITES
LACOO3
OXIDES
SM
EU
ND
Аннотация: The temperature dependence of the static magnetization of polycrystalline rare-earth cobaltite GdCoO3 is measured in the temperature range 2-800 K. The magnetic behaviors of GdCoO3 and Gd3+ are found to be different at temperatures above room temperature, which is caused by the appearance of a contribution from Co3+ ions at high temperatures. The temperature dependence of the magnetic susceptibility of GdCoO3 is determined by the magnetization of rare-earth gadolinium ions and the additional paramagnetic contribution induced by the thermally excited magnetic terms of Co3+ ions. The LDA + GTB method is used to calculate the electronic structure of GdCoO3 in the temperature range 0-300 K with allowance for strong electron correlations. The energy spectrum of GdCoO3 is found to have intragap states that decrease the dielectric gap width with increasing temperature.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fedorov A. S., Ovchinnikov S. G.
Заглавие : Density and thermodynamics of hydrogen adsorbed inside narrow carbon nanotubes
Разночтения заглавия :авие SCOPUS: Density and Thermodynamics of Hydrogen Adsorbed Inside Narrow Carbon Nanotubes
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2004. - Vol. 46, Is. 3. - P584-589. - ISSN 1063-7834, DOI 10.1134/1.1687883
Примечания : Cited References: 21. - This study was supported by the federal program “Integration,” project no. Б0017
Предметные рубрики: MOLECULAR-DYNAMICS
TRANSITIONS
TRANSPORT
ENERGY
TUBES
Аннотация: A model is proposed for calculating the thermodynamic functions and the equilibrium density of a one-dimensional chain of molecules (atoms) adsorbed inside a narrow nanotube. The model considers both the interaction between introduced atoms (molecules) and their interaction with the nanotube walls. The quantum-mechanical effects resulting in discrete energy levels of a particle and in its smeared position between neighbors are taken into account. In calculating the free energy at a nonzero temperature, the phonon contribution and the particle transitions to excited levels are considered. The model is applied to calculate the thermodynamic parameters of adsorbed hydrogen molecules inside extremely narrow single-wall carbon nanotubes of the (3,3) and (6,0) type. It is shown that external pressure gives rise to a sequence of first-order phase transitions, which change the density of adsorbed hydrogen molecules. (C) 2004 MAIK "Nauka / Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fedorov A. S., Sorokin P. B.
Заглавие : Density and thermodynamics of hydrogen adsorbed on the surface of single-walled carbon nanotubes
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2006. - Vol. 48, Is. 2. - P402-407. - ISSN 1063-7834, DOI 10.1134/S1063783406020351
Примечания : Cited References: 22
Предметные рубрики: MOLECULAR-DYNAMICS
ROOM-TEMPERATURE
STORAGE
ADSORPTION
H-2
TRANSITIONS
TUBES
Аннотация: A method is proposed for calculating the adsorption of hydrogen in single-walled carbon nanotubes. This method involves solving the Schrodinger equation for a particle (hydrogen molecule) moving in a potential generated by the surrounding hydrogen molecules and atoms forming the wall of the carbon nanotube. The interaction potential for hydrogen molecules is taken in the form of the Silvera-Goldman empirical potential, which adequately describes the experimental data on the interaction between H(2) molecules (including the van der Waals interaction). The interaction of hydrogen molecules with carbon atoms is included in the calculation through the Lennard-Jones potential. The free energy at a nonzero temperature is calculated with allowance made for the phonon contribution, which, in turn, makes it possible to take into account the correlations in the mutual arrangement of the neighboring molecules. The dependences of the total energy, the free energy, and the Gibbs thermodynamic potential on the applied pressure P and temperature T are calculated for adsorbed hydrogen molecules. These dependences are obtained for the first time with due regard for the quantum effects. The pressure and temperature dependences of the hydrogen density m(P, T) are also constructed for the first time.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S.
Заглавие : Effect of bond fluctuations on the transport properties of manganites and nickelates
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2007. - Vol. 104, Is. 5. - P766-774. - ISSN 1063-7761, DOI 10.1134/S1063776107050111
Примечания : Cited References: 26
Предметные рубрики: NEUTRON-DIFFRACTION
CHARGE DISPROPORTIONATION
ELECTRONIC-STRUCTURE
MAGNETIC ORDER
TRANSITIONS
PEROVSKITES
PRNIO3
GAP
Ключевые слова (''Своб.индексиров.''): crystal structure--manganites--optimization--thermal conductivity--thermal effects--bond fluctuations--nickelates--orthorhombic crystal structure--nickel compounds
Аннотация: For the manganites RMnO(3) (R = La, Pr, Nd), a mechanism is proposed to explain the anomalous temperature dependences of the kinetic coefficients, resistivity, and thermoelectric power during the transition from the pseudocubic O to the orthorhombic O' crystal structure. The contributions of the bending and stretching modes of the octahedron to the formation of thermal-conductivity maxima and to the deviation from the linear dependence of ln(rho/T) on 1/T at low temperatures have been estimated. In nickelates, the metal-insulator transition is caused by lattice-polaron pinning by the stretching mode of the octahedron, and the low-temperature anomaly of the thermal conductivity is related to electron scattering by the bending mode of the octahedron.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : PARLINSKI K., CURRAT R., VETTIER C., ALEKSANDROVA I. P., ECKOLD G.
Заглавие : Effect of hydrostatic-pressure on modulated phases in Rb2ZnBr4
Разночтения заглавия :авие SCOPUS: Effect of hydrostatic pressure on modulated phases in Rb2ZnBr4
Место публикации : Phys. Rev. B. - 1992. - Vol. 46, Is. 1. - P.106-114. - ISSN 0163-1829, DOI 10.1103/PhysRevB.46.106
Примечания : Cited References: 36
Предметные рубрики: INCOMMENSURATE PHASES
NEUTRON-SCATTERING
X-RAY
COMMENSURATE
TRANSITIONS
EVOLUTION
MODEL
WAVE
Аннотация: Neutron-diffraction studies on modulated Rb2ZnBr4, carried out under hydrostatic pressure, revealed two new commensurate phases characterized by wave vectors q = 2/7b* and q = 1/4b*, respectively. The first order phase transition between them is revealed by the coexistence of two distinct peaks in the diffraction pattern. The observed pressure-temperature phase diagram contains: the above-mentioned phases, the ferroelectric commensurate phase q = 1/3, and a region characterized by wave-vector values in the interval q = 2/7-1/3. In this region the modulation wave vector exhibits stepwise behavior as a function of pressure, but remains nearly constant iii temperature runs. We have found in this region a characteristic memory effect in which two temperature runs performed at the same pressure lead to two different modulation wave-vector values, while only the thermal history of the sample is different in the two runs. At ambient pressure we confirm the presence of a multipeaked diffraction pattern just above the lock-in transition to the commensurate q = 1/3 phase. At 122 K the phase transition from the 1/3 phase to the 1/4 phase is detected in pressure scans. The transition mechanism involves the q = 2/7 phase, at least as a metastable intermediate phase.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M., Ovchinnikov S. G., Sherman A. V.
Заглавие : Effective hamiltonian and properties of the normal and superconducting phases of n-type cuprates
Разночтения заглавия :авие SCOPUS: Effective Hamiltonian and properties of the normal and superconducting phases of n-type cuprates
Место публикации : JETP Letters. - 2004. - Vol. 80, Is. 1. - P.39-43. - ISSN 0021-3640, DOI 10.1134/1.1800212
Примечания : Cited References: 32
Предметные рубрики: T-J MODEL
ORDER-PARAMETER
QUASI-PARTICLES
COPPER OXIDES
FERMI-SURFACE
ELECTRON
SYMMETRY
RANGE
ND1.85CE0.15CUO4
TRANSITIONS
Аннотация: An effective low-energy Hamiltonian is derived from a microscopic multiband p-d model in the regime of strong electron correlations. The parameters of the p-d model are determined by comparison with the ARPES data for undoped Nd2CuO4. The Hamiltonian is the t-J* model in which hopping and exchange slowly decay with distance and are taken into account up to the fifth coordination sphere. The quasiparticle band structure is calculated as a function of the doping concentration with regard to short-range magnetic order, and the superconductivity theory with the spin-fluctuation pairing mechanism is constructed. Assuming that the parameters of the model do not depend on the doping level, we obtained quantitative agreement with the properties observed experimentally for the normal and superconducting phases without introducing fitting parameters. (C) 2004 MAIK "Nauka / Interperiodica".
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Platunov M. S., Kazak N. V., Dudnikov V. A., Temerov V. L., Gudim I. A., Knyazev Yu. V., Gavrilkin S. Yu., Dyadkin, Vadim, Dovgaliuk, Iurii, Chernyshov, Dmitry, Hen, Amir, Wilhelm, Fabrice, Rogalev, Andrei, Ovchinnikov S. G.
Заглавие : Element selective magnetism in Ho0.5Nd0.5Fe3(BO3)4 single crystal probed with hard X-ray magnetic circular dichroism
Коллективы : Russian Foundation for Basic Research [16-32-60049, 17-02-00826, 18-42-243007]; Foundation for Assistance to Small Innovative Enterprises (FASIE, UMNIK program)
Место публикации : J. Magn. Magn. Mater. - 2019. - Vol. 479. - P.312-316. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2019.02.040. - ISSN 1873-4766(eISSN)
Примечания : Cited References: 40. - The study was supported in part by the grants of the Russian Foundation for Basic Research (project Nos. 16-32-60049, 17-02-00826, 18-42-243007) and the Foundation for Assistance to Small Innovative Enterprises (FASIE, UMNIK program). The magnetic measurements were carried out in the Shared Facility Centre of P.N. Lebedev Physical Institute of RAS. We are grateful to Dr. Alexey Bosak for providing assistance of the structural experiments on the ID28 beamline. We are also grateful to Dr. Evgeniy Eremin from Kirensky Institute of Physics for providing the results of magnetic measurements and for useful discussions. The authors thank the ID12 beamline staffs for help during the XMCD experiment and also gratefully acknowledge the beamtime provision (proposal HC-1804) by the ESRF.
Предметные рубрики: MICROSTRUCTURE
TRANSITIONS
ND
Ключевые слова (''Своб.индексиров.''): x-ray magnetic circular dichroism--x-ray absorption--magnetic properties
Аннотация: We present a study of a Ho0.5Nd0.5Fe3(BO3)4 single crystal aiming at understanding the roles of each magnetic sublattices in magnetic transitions at low temperatures. The crystal structure is determined to have the R32 symmetry in whole studied temperature range but the crystal appears to be racemic. Element selective magnetic properties studied with X-ray magnetic circular dichroism at the L2,3-edges of Ho and Nd, and at the Fe K-edge at T = 3 K under magnetic fields of ±17 T are compared with the results of macroscopic magnetization measurements in pure and substituted crystals. All three magnetic sublattices are shown to be strongly coupled and to undergo a spin-reorientation transition when magnetic field is applied along the trigonal c-axis. On the contrary, when magnetic field is applied in the ab-plane only the holmium atoms exhibit a sizeable magnetization jump. This result allows us to conclude that the spin-flop transitions observed in macroscopic magnetization curves and associated anomalies of electric polarization are due to the Ho3+ magnetic moment reorientation.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Myagkov V. G., Bykova L. E., Bondarenko G. N.
Заглавие : Epitaxial B2-NiAl layers formed by nanosecond laser irradiation of thin Al/Ni bilayers
Место публикации : Tech. Phys. Lett.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2006. - Vol. 32, Is. 10. - P827-830. - ISSN 1063-7850, DOI 10.1134/S1063785006100026
Примечания : Cited References: 18
Предметные рубрики: POWDER MIXTURES
TRANSFORMATION
TRANSITIONS
OLIVINE
SURFACE
Аннотация: The results of experiments on the synthesis of epitaxial B2-NiAl layers by means of nanosecond laser irradiation of sequentially deposited thin nickel and aluminum layers (Al/Ni bilayers) on a MgO(001) substrate surface are presented. Features of the phase formation under the laser action and during the combustion wave initiation are considered. The rapid formation of an epitaxial B2-NiAl layer is explained in terms of a martensitic-like mechanism of the transfer of reacting atoms via a layer of reaction products. It is suggested that this mechanism can compete with diffusion via grain boundaries and dislocation, thus explaining the ultrafast transfer of reacting atoms via a layer of reaction products for various methods of initiation of the solid-state synthesis.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Val'kova T. A., Mitskan V. A.
Заглавие : Gapless chiral superconducting (d + id)-wave phase in strongly correlated layered material with a triangular lattice
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR) [19-02-00348, 18-42240014]; Krasnoyarsk Kray Science Foundation [18-42-240014]; Administration of the Krasnoyarsk Kray
Место публикации : J. Exp. Theor. Phys. - 2020. - Vol. 130, Is. 2. - P.235-246. - ISSN 1063-7761, DOI 10.1134/S1063776120010197. - ISSN 1090-6509(eISSN)
Примечания : Cited References: 44. - This study was supported by the Russian Foundation for Basic Research (project nos. 19-02-00348 and 18-42240014), the Administration of the Krasnoyarsk Kray, the Krasnoyarsk Kray Science Foundation within research project "Single-orbital Effective Model of Ensemble of Spin-Polaron Quasiparticles in the Problem of Description of the Intermediate State and Pseudogap Behavior of Cuprate Superconductors" (project no. 18-42-240014).
Предметные рубрики: TRANSITIONS
SPIN
Аннотация: It is shown that interlayer electron tunneling in the quasi-two-dimensional ensemble of Hubbard fermions leads to the realization of the gapless superconducting phase with the chiral (d + id)-wave order parameter symmetry, not for a single value of sodium ion concentration, but in a wide range of concentrations. Precisely this situation corresponds to experimental data on the layered sodium cobaltite intercalated by water (NaxCoO2 · yH2O). Intra-atomic electron repulsion that determines the strong electron correlation regime leads to the representation of Hubbard fermions, the interaction of which ensures Cooper instability. Intersite intralayer interactions between fermions considerably affect the positions of nodal points of the chiral order parameter and change the critical concentration at which a topological transition occurs in the 2D system of Hubbard fermions.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Gorev M. V., Sciau P.
Заглавие : Heat capacity and p-T phase diagrams of the ordered perovskites Pb2MgWO6 and Pb2CoWO6
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2000. - Vol. 12, Is. 5. - P.559-567. - ISSN 0953-8984, DOI 10.1088/0953-8984/12/5/304
Примечания : Cited References: 25
Предметные рубрики: CRYSTAL-STRUCTURE
X-RAY
TRANSITIONS
PRESSURE
Аннотация: The heat capacities of Pb2MgWO6 and Pb2CoWO6 and the effect of hydrostatic pressure on the phase transitions have been studied on powdered samples by means of an adiabatic calorimeter and DTA performed under pressure, respectively. Thermodynamic parameters, such as change of total excess entropy, latent hear and hysteresis of the phase transition temperature were determined. Entropies and p-T phase diagrams are discussed in connection with structural data.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pogoreltsev E. I., Flerov I. N., Kartashev A. V., Bogdanov E. V., Laptash N. M.
Заглавие : Heat capacity, entropy, dielectric properties and T–p phase diagram of (NH4)3TiF7
Коллективы : Russian Foundation for Basic Research [15-02-02009]; Council on Grants from the President of the Russian Federation for the Support of Leading Scientific Schools of the Russian Federation [NSh-924.2014.2]
Место публикации : J. Fluor. Chem.: Elsevier Science, 2014. - Vol. 168. - P.247-250. - ISSN 0022-1139, DOI 10.1016/j.jfluchem.2014.10.016. - ISSN 1873-3328
Примечания : Cited References: 16. - This work was supported by the Russian Foundation for Basic Research (Grant no. 15-02-02009), and the Council on Grants from the President of the Russian Federation for the Support of Leading Scientific Schools of the Russian Federation (Grant no. NSh-924.2014.2).
Предметные рубрики: CRYSTAL-STRUCTURE
TRANSITIONS
FLUORIDES
NH4F
Ключевые слова (''Своб.индексиров.''): cubic fluorides--phase transitions--dielectric--phase diagram--calorimetry
Аннотация: Successive phase transitions G1 -- G2 -- G3 in the double salt (NH4)(3)TiF7 have been studied by detailed calorimetric, DTA under hydrostatic pressure and dielectric measurements. Rather large entropy jumps at phase transition points were found to be followed by large additional contributions associated with the temperature dependence of the excess heat capacity. The permittivity behaviour and the tangent of the dielectric losses proved the nonferroelectric nature of both transformations. Two triple-points were found on the temperature-pressure phase diagram, suggesting the existence of a hypothetical parent G0 = Pm-3m cubic phase. A direct transformation between high (G0) and low (G3) temperature cubic phases takes place at p 0.41 GPa with a baric coefficient dT(G0) -- (G3)/dp = -40 K/GPa. (C) 2014 Elsevier B.V. All rights reserved.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fokina V. D., Flerov I. N., Molokeev M. S., Pogoreltsev E. I., Bogdanov E. V., Krylov A. S., Bovina A. F., Voronov V. N., Laptash N. M.
Заглавие : Heat capacity, p-T phase diagram, and structure of Rb2KTiOF5
Коллективы :
Разночтения заглавия :авие SCOPUS: Heat capacity, p-T phase diagram, and structure of Rb2KTiOF 5
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2008. - Vol. 50, Is. 11. - P2175-2183. - ISSN 1063-7834, DOI 10.1134/S1063783408110280
Примечания : Cited References: 23. - This work was supported by the Russian Foundation for Basic Research, project no. 06-02-16102.
Предметные рубрики: ELECTRON-DIFFRACTION
TRANSITIONS
OXYFLUORIDES
(NH4)(2)KWO3F3
TEMPERATURE
XRD
CS
Ключевые слова (''Своб.индексиров.''): 61--50--ks--65--40--ba--65--40--gd--78--30--hv--81--30--dz
Аннотация: Elpasolite Rb2KTiOF5 (space group, Fm was synthesized using a solid-phase reaction method. The temperature dependences of the heat capacity, the unit cell parameters, the structure, the permittivity, the response to an external pressure, and the Raman spectra were studied. A nonferroelectric phase transition was revealed at T (0) = 215 K; the transition is accompanied by a tetragonal distortion of the unit cell (space group I4/m, Z = 10) and a change in the entropy (S (0) = Rln8), which is anomalously large for perovskite-like oxyfluorides with atomic cations. The specific features of the mechanism of structure distortion are discussed in combination with the previous experimental data obtained for cryolite (NH4)(3)TiOF5 and elpasolite Rb2KGaF6.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Gorev M. V., Fokina V. D., Bovina A. F., Molokeev M. S., Pogorel'tsev E. I., Laptash N. M.
Заглавие : Heat capacity, structure, and p-T phase diagram of elpasolite (NH4)(2)KMoO3F3
Разночтения заглавия :авие SCOPUS: Heat capacity, structure, and p-T phase diagram of elpasolite (NH 4)2KMoO3F3
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2007. - Vol. 49, Is. 1. - P141-147. - ISSN 1063-7834, DOI 10.1134/S1063783407010234
Примечания : Cited References: 8
Предметные рубрики: TRANSITIONS
Аннотация: Thermophysical and structural studies of an (NH4)(2)KMoO3F3 crystal show that this crystal belongs to the family of elpasolites (space group Fm (3) over barm) and undergoes an order-disorder phase transition at To 241.5 K. Under hydrostatic pressure, this phase transition splits into two consecutive transitions at the tricritical point with parameters T-tr = 232.5 K and p(tr)= 0.21 GPa. It was found that anomalous hysteresis and relaxation phenomena accompany the transitions from the cubic to both distorted phases. The results are analyzed taking into account the data on the phase transition in the related elpasolite (NH4)(2)KWO3F3.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Chechin G. M., Sakhnenko V. P., Misyul S. V., Aleksandrov K. S.
Заглавие : Improper ferroelectric phase due to condensation of two order parameters in crystals of high-temperature superconductors
Место публикации : Ferroelectrics. - 1992. - Vol. 130, Is. 1. - P.155-162. - ISSN 0015-0193
Примечания : Cited References: 21
Предметные рубрики: TRANSITIONS
FERROELASTICS
RB3CD2CL7
Ключевые слова (''Своб.индексиров.''): ceramic materials--crystals--ferroelectricity--phase diagrams--order parameters--oxide superconductors--high temperature superconductors
Аннотация: Using group-theoretical methods it is shown that improper ferroelectric phase may arise in high-temperature superconductors (HTSC) where high-symmetry phases have space groups D4h1 or D4h17. Their appearance is caused by condensation of order parameters (OP's) transforming two irreducible representations (IR's). The most typical phase diagrams are considered, as well as temperature dependence of OP's and the basic structural mechanism of the ferroelectricity arising in the HTSC.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Popov A. K., Myslivets S. A., Gao J. Y., Zhang H. Z., Wellegehausen B.
Заглавие : Inversionless gain in a three-level system driven by a strong field and collisions
Место публикации : Chin. Phys. - 2000. - Vol. 9, Is. 2. - P.124-130. - ISSN 1009-1963
Примечания : Cited References: 45
Предметные рубрики: ELECTROMAGNETICALLY INDUCED TRANSPARENCY
POPULATION-INVERSION
LIGHT AMPLIFICATION
QUANTUM COHERENCE
REFRACTIVE-INDEX
LASER
INTERFERENCE
TRANSITIONS
SODIUM
ATOMS
Аннотация: Inversionless gain in a degenerate three-level system driven by a strong external field and by collisions with a buffer gas is investigated. The mechanism of population distribution in upper laser level, contributed by the collision transfer, as well as by relaxation, induced by pressure of a buffer gas, is discussed in detail. Explicit formulae for analysis of optimal conditions are derived. The idea developed here for the incoherent pump could be generalized to other systems.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorev M. V., Bogdanov E. V., Flerov I. N., Kocharova A. G., Laptash N. M.
Заглавие : Investigation of thermal expansion, phase diagrams, and barocaloric effect in the (NH4)(2)WO2F4 and (NH4)(2)MoO2F4 oxyfluorides
Коллективы :
Разночтения заглавия :авие SCOPUS: Investigation of thermal expansion, phase diagrams, and barocaloric effect in the (NH4)2WO2F4 and (NH4)2MoO2F4 oxyfluorides
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2010. - Vol. 52, Is. 1. - P167-175. - ISSN 1063-7834, DOI 10.1134/S1063783410010294
Примечания : Cited References: 27. - This study was performed within the framework of the Interdisciplinary Integration Project no. 34 of the Siberian Branch of the Russian Academy of Sciences and supported by the Krasnoyarsk Regional Science Foundation and the Russian Foundation for Basic Research within the framework of the project "Sibir'" ( grant no. 09-02-98001) and by the Council on Grants from the President of the Russian Federation for the Support of Leading Scientific Schools ( project no. NSh-1011.2008.2).
Предметные рубрики: TRANSITIONS
CRYSTALS
DIFFRACTION
MECHANISM
PRESSURE
Аннотация: The thermal expansion along the principal crystallographic axes of the (NH4)(2)WO2F4 and (NH4)(2)MoO2F4 oxyfluorides has been studied. The anomalous behavior of alpha (i) (T) due to the phase transitions has been revealed at T (1) = 271.4 K and T (2) a parts per thousand 180 K for the molybdate and at T (1) = 201.5 K and T (2) a parts per thousand 161 K for the tungstate. The quantities dT/dp and dT/d sigma (i) , which characterize the dependence of the phase transition temperatures on the hydrostatic and uniaxial pressures, have been determined from analyzing the results of studies of the thermal expansion and heat capacity with the use of the Pippard relations. The p-T and alpha (i) -T phase diagrams reflect different characters of the influence of the pressure on the stability of the initial and distorted phases of the oxyfluorides. The magnitudes of the extensive and intensive barocaloric effects determined in the vicinity of the structural phase transitions are as follows: Delta S (BCE) varies from approximately -10 to -17 J/mol K and Delta T (AD) a parts per thousand 8-17 K for the molybdate and Delta S (BCE) varies from approximately -10 to -17 J/mol K and Delta T (AD) a parts per thousand 8-13 K for the tungstate.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fedorov A. S., Avramov P. V., Ovchinnikov S. G., Kresse G.
Заглавие : Isotope velocity differentiation in thin carbon nanotubes through quantum diffusion
Место публикации : Europhys. Lett. - 2003. - Vol. 63, Is. 2. - P.254-260. - ISSN 0295-5075, DOI 10.1209/epl/i2003-00512-5
Примечания : Cited References: 17
Предметные рубрики: MOLECULAR-DYNAMICS
TRANSITIONS
TRANSPORT
ENERGY
Аннотация: An approach is proposed to evaluate the average velocities of adsorbate molecules in one-dimensional nanopore, when quantum tunneling between neighboring potential minima leads to nonzero velocity. The approach is used to calculate the hydrogen isotope molecule (H-2, D-2, T-2) velocities in ultrathin carbon single-wall nanotubes (SWNT) (3, 3) and (6, 0). It is shown that the isotope mass difference leads to large differences of the quantum tunneling value and large differences of the average molecule velocities, especially inside the tube (6, 0). It is shown that different tube chirality leads to drastically different velocities of adsorbate molecules, even if the diameters of both nanotubes do not differ significantly.
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