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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kveglis, Ludmila I., Noskov, Fedor M., Volochaev M. N., Nyavro, Alexander V., Filarowski, Aleksander
Заглавие : Magnetic properties of nickel-titanium alloy during martensitic transformations under plastic and elastic deformation
Место публикации : Symmetry. - 2021. - Vol. 13, Is. 4. - Ст.665. - ISSN 2073-8994(eISSN), DOI 10.3390/sym13040665
Примечания : Cited References: 61
Предметные рубрики: NITI SHAPE-MEMORY
CRYSTAL-STRUCTURE
WAVE MECHANICS
TRANSITIONS
Аннотация: This paper focuses on the processes of the occurrence of magnetization during structure formation in samples of Ni51Ti49 alloy under deformation conditions. The possibility of the existence of a phase with an FCC (face-centered cubic) lattice in titanium nickelide has been demonstrated by electron microscopy and electron diffraction. It has been discovered that the interplanar distances of BCC110 (body-centered cubic), FCC111, and HCP002 (hexagonal close packed) in the alloy under study have similar values, which indicates the possibility of their mutual polymorphic transformation. Based on the modular self-organization, a scheme of martensitic transformations in titanium nickelide from the B2 structure (BCC lattice) to the B19' structure (HCP lattice) through an intermediate phase with an FCC lattice is proposed. It is shown that lenticular crystals appear in the Ni51Ti49 alloy under tensile deformation until rupture, which is accompanied by the onset of ferromagnetism. The effect of magnetization in Ni51Ti49 samples when immersed in liquid nitrogen has been also discovered. In this case, the reason for the appearance and disappearance of magnetization can be associated with microdeformation processes caused by direct and reverse martensitic transitions that occur during cooling and heating of the samples.
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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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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Dudnikov V. A., Fedorov A. S., Orlov Yu. S., Solovyov L. A., Vereshchagin S. N., Gavrilkin, S. Yu, Tsvetkov, A. Yu, Gorev M. V., Novikov, S., V, Ovchinnikov S. G.
Заглавие : Thermoelectric properties of the SmCoO3 and NdCoO3 cobalt oxides
Коллективы : Russian Science FoundationRussian Science Foundation (RSF) [16-13-00060]
Место публикации : Ceram. Int. - 2020. - Vol. 46, Is. 11. - P.17987-17991. - ISSN 0272-8842, DOI 10.1016/j.ceramint.2020.04.113. - ISSN 1873-3956(eISSN)
Примечания : Cited References: 41. - This study was supported by the Russian Science Foundation, project no. 16-13-00060.
Предметные рубрики: MAGNETIC-PROPERTIES
SPIN
CONDUCTIVITY
TRANSITIONS
LACOO3
SITE
Аннотация: The thermoelectric properties of the NdCoO3 and SmCoO3 rare-earth cobalt oxides with a perovskite structure have been investigated in a wide temperature range. It is shown that, in the low-temperature region, the thermal conductivity of the compounds has a sharp maximum and the electrical conductivity of the samples increases with temperature, whereas the Seebeck coefficient behaves nonmonotonically with increasing temperature. The SmCoO3 oxide is characterized by the positive thermopower over the entire investigated range with a sharp growth in the low-temperature region, attaining the maximum value (S ≈ 1000 μV/K) near room temperature, and a further decrease. It has been established that, in the NdCoO3 oxide, the Seebeck coefficient changes its sign, which was rarely observed in the La-based compounds and is atypical of the undoped rare-earth cobalt oxides. The thermopower maximum obtained at a temperature of 450 K is 400 μV/K. The regions of the fastest growth of the thermoelectric power factor correspond to the anomalies caused by the spin transition of Со3+ ions and the dielectric–metal transition.
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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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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Rudyak, V. Yu., Krakhalev M. N., Prishchepa O. O., Sutormin V. S., Emelyanenko A. V., Zyryanov V. Ya.
Заглавие : Orientational structures in nematic droplets with conical boundary conditions
Коллективы : Russian Foundation for Basic Research; Government of the Krasnoyarsk region [16-42-240704 r_a]; Russian Foundation for Basic Research [16-32-00164, 15-02-08269, 15-59-32410]
Место публикации : JETP Letters. - 2017. - Vol. 106, Is. 6. - P.384-389. - ISSN 0021-3640, DOI 10.1134/S0021364017180102. - ISSN 1090-6487(eISSN)
Примечания : Cited References:34. - This work was supported by the Russian Foundation for Basic Research and the Government of the Krasnoyarsk region (project no. 16-42-240704 r_a). The work of M.N. Krakhalev and V.S. Sutormin on the experimental study and analysis of the orientational structures of nematic droplets was supported by the Russian Foundation for Basic Research (project no. 16-32-00164). The work of V.Yu. Rudyak and A.V. Emelyanenko on the theoretical analysis of the structures of liquid crystal droplets was supported by the Russian Foundation for Basic Research (project nos. 15-02-08269 and 15-59-32410).
Предметные рубрики: DISPERSED LIQUID-CRYSTALS
TOPOLOGICAL DEFECTS
FIELD
TRANSITIONS
Аннотация: Oblate nematic droplets encapsulated in a polymer specifying conical boundary conditions have been considered. Calculations by the extended Frank elastic continuum approach show that a number of various structures can be formed in such droplets under the variation of their size. Polarizing optical microscopy studies of composite film samples confirm the results of calculation and demonstrate the formation of the following orientational structures in the considered system: (i) a radial-bipolar structure with a twisted hedgehog defect and two hyperbolic boojums, (ii) an axial-bipolar structure with a circular disclination and two radial boojums, and (iii) a structure with a hedgehog defect, a hyperbolic boojum, and a radial boojum. Such a diversity of possible topologies of droplets is due to a complex balance between the energies of elasticity of the director field, disclinations, and anchoring with the surface, which is ensured by conical boundary conditions.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krylov A. S., Gudim, I. A., Nemtsev I. V., Krylova S. N., Shabanov A. V., Krylov A. A.
Заглавие : Raman study of HoFe3(BO3)4 at simultaneously high pressure and high temperature: p–T phase diagram
Коллективы : International GeoRAMAN Conference
Место публикации : J. Raman Spectrosc. - 2017. - Vol. 48, Is. 11. - P.1406-1410. - ISSN 0377-0486, DOI 10.1002/jrs.5078. - ISSN 1097-4555(eISSN)
Примечания : Cited References:35. - Authors are grateful to Prof. A.N. Vtyurin for his valuable discussion. This work was supported by the Russian Foundation for Basic Research (grant no. 17-02-00694)
Предметные рубрики: HYDRATE FORMATION
SINGLE-CRYSTALS
WATER SYSTEM
TRANSITIONS
Ключевые слова (''Своб.индексиров.''): phase transitions--high hydrostatic pressure--ferroborates--p-t phase--diagram--nanocrystal
Аннотация: Raman spectra of a HoFe3(BO3)4 crystal chip has been investigated at simultaneously high temperature and high pressure (up to 7.1 GPa and 560 K). On the basis of Raman analysis, the assignment to one of the two possible crystal phases has been made. The experimental p–T phase diagram of HoFe3(BO3)4 was established. An increase in the pressure leads to an increase in the temperature of transition. The phase boundary equation was obtained. Neither triple points nor a phase with new symmetry was revealed in the phase diagram. A critical point with the temperature T = 560 K and the pressure p = 2.53 GPa was found. The nanocrystals with different shapes began to grow on crystal surface after reaching that point. The composition of new nanocrystals is identical to the composition of initial crystal.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Loiko V. A., Zyryanov V. Ya., Konkolovich A. V., Miskevich A. A.
Заглавие : Light transmission of polymer-dispersed liquid crystal layer composed of droplets with inhomogeneous surface anchoring
Место публикации : Opt. Spectrosc.: MAIK Nauka-Interperiodica / Springer, 2016. - Vol. 120, Is. 1. - P.143-152. - ISSN 0030-400X, DOI 10.1134/S0030400X16010112. - ISSN 1562-6911(eISSN)
Примечания : Cited References:43. - This work was supported by the National Academy of Sciences of Belarus and the Siberian Branch of the Russian Academy of Sciences (project no. 36) and the Belarusian Republican Foundation for Fundamental Research (project no. F15SO-039).
Предметные рубрики: NEMATIC DROPLETS
IONIC MODIFICATION
FIELD
TRANSITIONS
SCATTERING
PARTICLES
INTERFACE
DISPLAYS
Аннотация: We have developed a model and realized an algorithm for the calculation of the coefficient of coherent (direct) transmission of light through a layer of liquid crystal (LC) droplets in a polymer matrix. The model is based on the Hulst anomalous diffraction approximation for describing the scattering by an individual particle and the Foldy-Twersky approximation for a coherent field. It allows one to investigate polymer dispersed LC (PDLC) materials with homogeneous and inhomogeneous interphase surface anchoring on the droplet surface. In order to calculate the configuration of the field of the local director in the droplet, the relaxation method of solving the problem of minimization of the free energy volume density has been used. We have verified the model by comparison with experiment under the inverse regime of the ionic modification of the LC-polymer interphase boundary. The model makes it possible to solve problems of optimization of the optical response of PDLC films in relation to their thickness and optical characteristics of the polymer matrix, sizes, polydispersity, concentration, and anisometry parameters of droplets. Based on this model, we have proposed a technique for estimating the size of LC droplets from the data on the dependence of the transmission coefficient on the applied voltage.
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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) : Mel'nikova S. V., Laptash N. M.
Заглавие : Optical studies of the (T-x) phase diagram of oxyfluoride (NH4)2MoO2F4-Rb2MoO2F4 solid solutions
Коллективы : Russian Federation [NSh-924.2014.2]
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2015. - Vol. 57, Is. 6. - P.1201-1205. - ISSN 1063, DOI 10.1134/S1063783415060256. - ISSN 10906460(eISSN)
Примечания : Cited References:8. - This study was supported by the Council on Grants from the President of the Russian Federation for Supporting of Leading Scientific Schools of the Russian Federation (grant NSh-924.2014.2).
Предметные рубрики: TRANSITIONS
(NH4)2WO2F4
CRYSTALS
DISORDER
Аннотация: Single crystals of solid solutions (NH4)2 − x Rb x MoO2F4 (including individual complex Rb2MoO2F4) have been grown and studied using polarization-optical methods. The birefringence Δn(T) has been measured in the temperature range of 100–400 K. The complete (T-x) phase diagram has been constructed.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Safonov I. N., Misyul' S. V., Molokeev M. S., Ivliev M. P.
Заглавие : Structural transformations and phenomenological description of the formation of phase states in elpasolites Cs2RbDyF6 and Rb2KB′F6 (B′ = Ho, Dy, Tb)
Коллективы : Ministry of Education and Science of the Russian Federation [3.2534.2014/K]
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2015. - Vol. 57, Is. 3. - P.491-498. - ISSN 1063, DOI 10.1134/S1063783415030282. - ISSN 10906460(eISSN)
Примечания : Cited References:20. - This study was supported by the Ministry of Education and Science of the Russian Federation within the framework of the State Task for the Russian Siberian Federal University for Implementation of Scientific Research Work in 2014 (assignment no. 3.2534.2014/K).
Предметные рубрики: TRANSITIONS
CRYSTALS
Аннотация: The structures of the cubic and monoclinic phases of an Rb2KHoF6 crystal from a series of elpasolites Rb2KB′F6 (B′ = Ho, Dy, Tb), which undergoes a trigger phase transition, have been investigated using X-ray powder diffraction. The critical and noncritical displacements of atoms in the Rb2KHoF6 structure have been determined from the group-theoretical analysis of the complete condensate of order parameters. It has been reliably established that a change in the symmetry due to the phase transition in this crystal can be represented in the form Fmˉ3m11−9(Γ+4)⊕10−3(X+3)(ϕ,ϕ,ψ)P121/n1Fm\bar 3m\frac{{11 - 9(\Gamma _4. + ) \oplus 10 - 3(X_3. + )}} {{(\phi ,\phi ,\psi )}}P12_1 /n1 . A phenomenological analysis of the conditions responsible for the formation of phase states upon the phase transitions in elpasolites Cs2RbDyF6 and Rb2KB′F6 (B′ = Ho, Dy, Tb) has been carried out. Taking into account the structural data and using the phenomenological theory, it has been found that the main factor determining the formation of phase states in these and related crystals is the instability of the elpasolite structure with respect to rotational distortions of two types. It has been shown that an important role in the formation of a sequence of structural transformations in these crystals is played by the interaction of rotational order parameters and displacements of the cation from the center of a cuboctahedral hole.
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11.

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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12.

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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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Slyusareva E. A., Tomilin F. N., Sizykh A. G., Tankevich E. Y., Kuzubov A. A., Ovchinnikov S. G.
Заглавие : The effect of halogen substitution on the structure and electronic spectra of fluorone dyes
Место публикации : Opt. Spectrosc.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2012. - Vol. 112, Is. 5. - P.671-678. - ISSN 0030-400X, DOI 10.1134/S0030400X12040194
Примечания : Cited References: 44. - This work was supported by the FTsP Kadry GK-P333 and by the Siberian Branch of the Russian Academy of Sciences (Integration project no. 2). We are grateful to the Joint Supercomputer Center of the Russian Academy of Sciences (Moscow) and to the Complex of High-Performance Computations of the IKIT of Siberian Federal University. E. A. Slyusareva acknowledges support from the German Academic Exchange Service and the Ministry of Education and Science of the Russian Federation (the program "Mikhail Lomonosov II") of scientific research at the University of Regensburg and in the Helmholtz Center in Berlin (Germany).
Предметные рубрики: POLARIZABLE CONTINUUM MODEL
BORIC-ACID GLASS
XANTHENE DYES
FLUORESCEIN DERIVATIVES
DELAYED FLUORESCENCE
EOSIN-Y
ABSORPTION
PHOSPHORESCENCE
TRANSITIONS
EXCITATION
Аннотация: By means of the B3LYP density functional method with the use of the polarized continuum model PCM, we have performed quantum-chemical computations of the electronic absorption and fluorescence spectra of fluorone dianions: fluorescein, dibromofluorescein, eosin, erythrosine, and Rose Bengal in vacuum and methanol. We have revealed conformational features of the structure of fluorone dianions (charge redistribution, changes in the bond lengths and angles between bonds) second by the halogen substitution, the transition from the ground state to an excited state, and the change of the solvent (vacuum-methanol). Absorption and fluorescence wavelengths, constant dipole moments, transition dipole moments, and oscillator strengths have been calculated. We have showed that, upon halogenation of fluorones, the absorption spectra are redshifted and the Stokes shift decreases, which is qualitatively consistent with experimental results.
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14.

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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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Malakhovskii A. V., Sukhachev A. L., Leont'ev A. A., Gudim, I. A., Krylov A. S., Aleksandrovsky A. S.
Заглавие : Spectroscopic properties of Nd0.5Gd0.5Fe3(BO3)4 single crystal
Место публикации : J. Alloys Compd.: Elsevier, 2012. - Vol. 529. - P.38-43. - ISSN 0925-8388, DOI 10.1016/j.jallcom.2012.03.066
Примечания : Cited References: 51. - The work was supported by the Russian Foundation for Basic Researches grant 12-02-00026, by the Russian President Grants SS-1044.2012.2 and SS-4828.2012.2, by Ministry of Education and Science of Russian Federation (Contract 16.740.11.0150), by grant no. SFU.F12 and by Projects No. 28, 43 and No. 101 of SB RAS.
Предметные рубрики: SPECTRAL-LINE INTENSITIES
RARE-EARTH IONS
MAGNETIC-PROPERTIES
NDAL3(BO3)(4) NAB
OPTICAL-SPECTRA
LASER CRYSTAL
TRANSITIONS
ABSORPTION
ND3+
PR3+
Ключевые слова (''Своб.индексиров.''): magnetically ordered materials--rare earth alloys and compounds--transition metal alloys and compounds--optical properties
Аннотация: The polarized absorption spectra of trigonal single crystal Nd0.5Gd0.5Fe3(BO3)4 were measured in the spectral range 10,000–22,000 cm−1. The d–d and f–f transitions spectra were separated. The f–f transitions intensities were analyzed in terms of the Judd–Ofelt theory in a ferroborate with huntite structure for the first time, and the following parameters of the theory were obtained: Ω2 = 4.4 × 10−20 cm2, Ω4 = 8.04 × 10−20 cm2, and Ω6 = 8.25 × 10−20 cm2. The strengths, spontaneous emission probabilities, branching ratios, spectroscopic quality factor and excited state lifetime were calculated for transitions from the 4F3/2 state to 4IJ manifold. All the obtained spectroscopic characteristics were compared with those of alumoborates with the same crystal structure.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fokina V. D., Bovina A. F., Bogdanov E. V., Pogorel'tsev E. I., Laptash N. M., Gorev M. V., Flerov I. N.
Заглавие : Specific heat, cell parameters, phase T-p diagram, and permittivity of cryolite (NH4)(3)Nb(O-2)(2)F-4
Разночтения заглавия :авие SCOPUS: Specific heat, cell parameters, phase T-p diagram, and permittivity of cryolite (NH4)3Nb(O2)2F4
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 53, Is. 10. - P2147-2153. - ISSN 1063-7834, DOI 10.1134/S1063783411100131
Примечания : Cited References: 19. - This study was performed within the Interdisciplinary integration project of the Siberian Branch of the Russian Academy of Science no. 34 and supported by the grant of the President of the Russian Federation for Leading Scientific Schools of the Russian Federation (NSh-4645.2010.2).
Предметные рубрики: CRYSTAL-STRUCTURES
TRANSITIONS
(NH4)(3)TIOF5
OXYFLUORIDE
COMPLEXES
CAPACITY
DISORDER
Аннотация: The temperature dependences of the specific heat, unit cell parameters, susceptibility to hydrostatic pressure, and permittivity of cryolite (NH4)(3)Nb(O-2)(2)F-4 have been studied. Phase transitions of nonferroelectric nature have been detected. Entropy parameters point to the relation of structure distortions to ordering processes.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pogorel'tsev E. I., Bogdanov E. V., Molokeev M. S., Voronov V. N., Isaenko L. I., Zhurkov S. A., Laptash N. M., Gorev M. V., Flerov I. N.
Заглавие : Thermodynamic Properties and Structure of Oxyfluorides Rb(2)KMoO(3)F(3) and K(2)NaMoO(3)F(3)
Разночтения заглавия :авие SCOPUS: Thermodynamic properties and structure of oxyfluorides Rb2KMoO3F3 and K2NaMoO3F3
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 53, Is. 6. - P1202-1211. - ISSN 1063-7834, DOI 10.1134/S1063783411060266
Примечания : Cited References: 24. - This study was supported by the Siberian Branch of the Russian Academy of Sciences within the framework of the Interdisciplinary Integration project no. 34 SO RAN and the Council on Grants from the President of the Russian Federation for Support of Leading Scientific Schools of the Russian Federation (project no. NSh-4645-2010.2).
Предметные рубрики: T PHASE-DIAGRAM
HEAT-CAPACITY
TRANSITIONS
(NH4)(3)MOO3F3
(NH4)(3)TIOF5
(NH4)(3)WO3F3
RB2KTIOF5
CRYSTALS
CRYOLITE
DISORDER
Аннотация: According to the results of calorimetric and structural studies, the Fm (3) over barm phase in K(2)NaMoO(3)F(3) remains stable at least to 100 K. No ferroelectric transformation assumed earlier has been revealed in a series of Rb(2)KMoO(3)F(3) samples prepared using various technologies. Only a phase transition of nonferroelectric origin has been observed near 195 K, and its thermodynamic characteristics have been determined. An analysis of the stability of the cubic structure of molybdenum fluorine-oxygen elpasolites-cryolites has been performed in the framework of the hypothesis on strengths of interatomic bonds. The barocaloric effect in Rb(2)KMoO(3)F(3) has been estimated.
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18.

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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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Popova M. N., Stanislavchuk T. N., Malkin B. Z., Bezmaternykh L. N.
Заглавие : Optical spectroscopy of PrFe3(BO3)(4): Crystal-field and anisotropic Pr-Fe exchange interactions
Коллективы : Russian Foundation for Basic Research [07-02-01185, 09-02-00930]; Russian Academy of Sciences under the Programs for Basic Research
Разночтения заглавия :авие SCOPUS: Optical spectroscopy of PrFe3 (BO3) 4: Crystal-field and anisotropic Pr-Fe exchange interactions
Место публикации : Phys. Rev. B. - 2009. - Vol. 80, Is. 19. - Ст.195101. - ISSN 1098-0121, DOI 10.1103/PhysRevB.80.195101
Примечания : Cited References: 36. - We thank S. Klimin for useful information concerning the structure of PrFeINF3/INF(BOINF3/INF)INF4/INF and E. Chukalina for participating in some measurements. This work was supported in part by the Russian Foundation for Basic Research (Grants No. 07-02-01185 and No. 09-02-00930) and by the Russian Academy of Sciences under the Programs for Basic Research.
Предметные рубрики: TRIGONAL GDFE3(BO3)(4)
NDFE3(BO3)(4)
DYFE3(BO3)(4)
TRANSITIONS
BORATE
ION
ND
Ключевые слова (''Своб.индексиров.''): antiferromagnetic materials--crystal field interactions--exchange interactions (electron)--infrared spectra--iron compounds--magnetic susceptibility--magneto-optical effects--paramagnetic materials--praseodymium compounds--spin hamiltonians--visible spectra
Аннотация: High-resolution polarized optical absorption spectra of PrFe3(BO3)(4) in the paramagnetic and antiferromagnetic phases are reported. The measured energies of the crystal-field (CF) levels within the 4f(2) configuration of Pr3+ in the paramagnetic PrFe3(BO3)(4) are described by the CF model that involves the 4f(2)/4f5d and 4f(2)/4f6p configuration interactions. Ordering of Fe spins along the crystalline c axis below T-N=32 K is confirmed by the analysis of the spectra of Er3+ introduced as a probe into PrFe3(BO3)(4). To account for the observed changes in the optical spectra of Pr3+ at temperatures below T-N, in particular, for the shift of the CF levels, splitting of the CF doublets, and the appearance of forbidden lines, the Pr-Fe exchange Hamiltonian defined by seven parameters is considered. The theoretical approach has been tested by calculating the temperature dependence of the magnetic susceptibility. A good agreement between theory and optical and magnetic experimental data is found demonstrating the validity of the model used. The obtained results confirm that the model of the iron dimers inside the spiral chains of Fe3+(O2-)(6) octahedrons introduced by us earlier for NdFe3(BO3)(4) and modified in the present work may serve as a basis for analyzing the low-temperature properties of other rare-earth iron borates.
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20.

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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