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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Avramov P. V., Minami S., Morokuma K., Irle S., Chernozatonskii L.A.
Заглавие : Atomic Structure and Energetic Stability of Complex Chiral Silicon Nanowires
Место публикации : J. Phys. Chem. C. - 2010. - Vol. 114, Is. 35. - P.14692-14696. - SEP 9. - ISSN 1932-7447, DOI 10.1021/jp1016399
Примечания : Cited Reference Count: 36. - Гранты: This work was supported by a CREST (Core Research for Evolutional Science and Technology) grant in the Area of High Performance Computing for Multiscale and Multiphysics Phenomena from the Japan Science and Technology Agency (JST) and a collaborative RFBR-JSPS grant No. 09-02-92107-Phi. S.I. also acknowledges support by the Program for Improvement of Research Environment for Young Researchers from Special Coordination Funds for Promoting Science and Technology (SCF) commissioned by the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan. L.Ch. acknowledges support by the Presidium of Russian Academy of Sciences (Program No. 27).Финансирующая организация: CREST (Core Research for Evolutional Science and Technology); Japan Science and Technology Agency (JST); RFBR-JSPS [09-02-92107]; Special Coordination Funds for Promoting Science and Technology (SCF); Presidium of Russian Academy of Sciences [27]
Предметные рубрики: DENSITY-FUNCTIONAL METHODS
GROWTH
EXCHANGE
NANOHELICES
NANOSPRINGS
Ключевые слова (''Своб.индексиров.''): ab initio--atomic structure--chiral complexes--consecutive shifts--dft method--energetic stability--homo-lumo gaps--metastable structures--potential barriers--si atoms--silicon nanowires--unit cell parameters--atoms--chirality--electronic structure--enantiomers--metastable phases--nanowires--stereochemistry--wire--crystal atomic structure
Аннотация: Atomic and electronic structure and energetic stability of newly proposed pentagonal and hexagonal chiral complex silicon nanowires (NWs) composed of five or six (I 10) oriented crystalline fragments were studied using the ab initio DFT method. The chirality of the wires was caused by consecutive shifts of each fragment by 1/5 or 1/6 of the wire unit cell parameter and rotations of 4 degrees and 3.3 degrees for achiral pentagonal or hexagonal wires, respectively. Chirality causes the HOMO-LUMO gap to reduce by 0.1 eV. Chiral silicon nanowires are found to be metastable structures with a 4,5 (kcal/mol)/Si atom potential barrier for reversible chiral achiral transformation.
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Sorokin P. B., Ovchinnikov S. G., Avramov P. V., Chernozatonskii L.A., Fedorov D.G.
Заглавие : Atypical quantum confinement effect in silicon nanowires
Место публикации : J. Phys. Chem. A. - WASHINGTON: AMER CHEMICAL SOC, 2008. - Vol. 112, Is. 40. - С. 9955-9964. - OCT 9. - ISSN 1089-5639, DOI 10.1021/jp805069b
Примечания : Cited Reference Count: 25. - Гранты: This work was in part partially supported by a CREST (Core Research for Evolutional Science and Technology) grant in the Area of High Performance Computing for Multiscale and Multiphysics Phenomena from the Japan Science and Technology Agency (JST) as well as by Russian Fund of Basic Researches (grant 08-02-01096) (L.A.C.). P.V.A. acknowledges the encouragement of Dr. Keiji Morokuma, Research Leader at Fukui Institute for Fundamental Chemistry. The geometry of all presented structures was visualized by ChemCraft software.SUP25/SUP L.A.C. acknowledges I. V. Stankevich for help and fruitful discussions. P.B.S. is grateful to the Joint Supercomputer Center of the Russian Academy of Sciences for access to a cluster computer for quantum-chemical calculations.Финансирующая организация: Japan Science and Technology Agency (JST); Russian Fund of Basic Researches [08-02-01096]
Предметные рубрики: ELECTRONIC-STRUCTURE
OPTICAL-PROPERTIES
SI
DENSITY
WIRES
EXCHANGE
ATOMS
DOTS
Ключевые слова (''Своб.индексиров.''): electric wire--energy gap--gallium alloys--mathematical models--nanostructured materials--nanostructures--nanowires--quantum confinement--quantum electronics--semiconductor quantum dots--silicon--ami methods--band gaps--blue shifts--dinger equations--linear junctions--monotonic decreases--quantum confinement effects--quantum dots--semiempirical--silicon nanowires--system sizes--theoretical models--nanocrystalline silicon--nanowire--quantum dot--silicon--article--chemistry--electron--quantum theory--electrons--nanowires--quantum dots--quantum theory--silicon
Аннотация: The quantum confinement effect (QCE) of linear junctions of silicon icosahedral quantum dots (IQD) and pentagonal nanowires (PNW) was studied using DFT and semiempirical AM1 methods. The formation of complex IQD/PNW structures leads to the localization of the HOMO and LUMO on different parts of the system and to a pronounced blue shift of the band gap; the typical QCE with a monotonic decrease of the band gap upon the system size breaks down. A simple one-electron one-dimensional Schrodinger equation model is proposed for the description and explanation of the unconventional quantum confinement behavior of silicon IQD/PNW systems. On the basis of the theoretical models, the experimentally discovered deviations from the typical QCE for nanocrystalline silicon are explained.
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Khalyapin D. L., Kim P. D., Kim J., Turpanov I. A., Beten'kova A. Ya., Bondarenko G. V., Isaeva T. N., Kim I.
Заглавие : Effect of alloy formation processes in the Co-Cu system on the magnetic and magnetoresistance properties of multilayer Co/Cu films with ultrathin Co layers prepared by DC magnetron sputtering
Место публикации : Phys. Solid State. - 2010. - Vol. 52, Is. 9. - P.1787-1796. - ISSN 1063-7834, DOI 10.1134/S1063783410090015
Примечания : Cited References: 29
Предметные рубрики: GIANT MAGNETORESISTANCE
SIZE DISTRIBUTION
SPIN VALVES
EXCHANGE
TEMPERATURE
HYSTERESIS
ANISOTROPY
CU(001)
ISLANDS
Аннотация: This paper reports on a study of multilayer Co/Cu films with an effective thickness of the Co layer of similar to 3.5 , which were prepared by magnetron sputtering. The samples prepared have been found to have a metastable multiphase structure. An analysis of the data obtained by structural and, primarily, by magnetic methods has revealed that the main phases are the Co/Cu supersaturated solid solution (alloy) with a Co concentration of about 30 at %, the superparamagnetic phase, and the paramagnetic phase, which is accounted for by the presence of small (a few atoms at most) Co clusters embedded in the Cu matrix. A clearly pronounced maximum in the temperature dependences of the low-field magnetoresistance has been found, which is associated with the temperature of the magnetic phase transition of the supersaturated Co-Cu alloy.
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Nyavro A. V., Cherepanov V. N., Arkhipkin V. G., Kveglis L. I., Musikhin V. A.
Заглавие : Electronic structure of grain boundaries in the Fe-86-Mn-12.7-C(1.3)alloy
Разночтения заглавия :авие SCOPUS: Electronic structure of grain boundaries in the Fe86-Mn 12.7-C1.3alloy
Место публикации : Russ. Phys. J.: SPRINGER, 2008. - Vol. 51, Is. 9. - P973-979. - ISSN 1064-8887, DOI 10.1007/s11182-009-9127-5
Примечания : Cited References: 13
Предметные рубрики: FERROMAGNETIC IRON
EXCHANGE
Аннотация: The importance of studying Fe-Mn-C alloys is related to their wide use as constructional materials in mechanical engineering. In this work an effort has been made to elucidate the physical origin of the magnetization in austenitic steels by calculating the electronic structure of grain boundaries. To theoretically investigate the magnetic properties of a crystal of ferromagnetic bcc iron, the wave functions of the iron atom calculated in view of the spin polarization of a core by the Hartree-Fock method with local exchange-correlation potentials have been used as base functions. This has made it possible to optimize the choice of a zero approximation for the description of the electronic states of ferromagnetic iron and to attain good agreement with the experimental values of the magnetic moment (A mu(theor) = 2.23A mu(B), A mu(exp) = 2.218A mu(B)), of the exchange splitting of the crystal term P-4 (Delta(theor) = Delta(exp) = 0.112 Ry), and of the cross-sections of the Fermi surface. A similar approach has been used to investigate the magnetic states of clusters (nanoclusters) based on the method of scattered waves. The approach developed for clusters of the alloy under investigation makes it possible to calculate the alloy magnetic properties in relation to the cluster size for a varied lattice parameter.
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5.

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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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krasnov P. O., Eliseeva N. S., Kuzubov A. A.
Заглавие : Interaction of Scandium and Titanium Atoms with a Carbon Surface Containing Five- and Seven-Membered Rings
Коллективы : Ministry of Education and Science of the Russian Federation
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2012. - Vol. 114, Is. 1. - P.80-84. - ISSN 1063-7761, DOI 10.1134/S1063776111160059. - ISSN 1090-6509
Примечания : Cited References: 25. - We are grateful to the Joint Supercomputer Center, Russian Academy of Sciences, for the possibility of using the computer cluster for our quantum-chemical calculations. This work was supported by the Ministry of Education and Science of the Russian Federation (federal program "Human Capital for Science and Education in Innovative Russia" for 2009-2013).
Предметные рубрики: MOLECULAR-HYDROGEN COMPLEXES
STORAGE
NANOTUBES
TRANSITION
ENERGY
TEMPERATURE
EXCHANGE
DYNAMICS
METALS
C60
Аннотация: The use of carbon nanotubes coated by atoms of transition metals to store molecular hydrogen is associated with the problem of the aggregation of these atoms, which leads to the formation of metal clusters. The quantum-chemical simulation of cluster models of the carbon surface of a graphene type with scandium and titanium atoms has been performed. It has been shown that the presence of five- and seven-membered rings, in addition to six-membered rings, in these structures makes it possible to strongly suppress the processes of the migration of metal atoms over the surface, preventing their clustering.
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Stolyar S. V., Yaroslavtsev R. N., Iskhakov R. S., Bayukov O. A., Balaev D. A., Dubrovskii A. A., Krasikov A. A., Ladygina V. P., Vorotynov A. M., Volochaev M. N.
Заглавие : Magnetic and resonance properties of ferrihydrite nanoparticles doped with cobalt
Коллективы : Ministry of Education and Science of the Russian Federation within the framework of the Special Program for the Siberian Federal University; Russian Foundation for Basic Research (RFBR) [16-03-00969]; Russian Foundation for Basic Research; Krasnoyarsk Regional Science Foundation (RFBR-KRSFr) [15-42-04171]
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2017. - Vol. 59, Is. 3. - P.555-563. - ISSN 1063-7834, DOI 10.1134/S1063783417030301. - ISSN 1090-6460(eISSN)
Примечания : Cited References:30. - This study was supported by the Ministry of Education and Science of the Russian Federation within the framework of the Special Program for the Siberian Federal University, the Russian Foundation for Basic Research (RFBR project no. 16-03-00969), and jointly by the Russian Foundation for Basic Research and the Krasnoyarsk Regional Science Foundation (RFBR-KRSFr-sibir'-a project no. 15-42-04171).
Предметные рубрики: 6-LINE FERRIHYDRITE
BACTERIAL FERRIHYDRITE
NIO NANOPARTICLES
EXCHANGE
Аннотация: Powders of undoped ferrihydrite nanoparticles and ferrihydrite nanoparticles doped with cobalt in the ratio of 5: 1 have been prepared by hydrolysis of 3d-metal salts. It has been shown using Mössbauer spectroscopy that cobalt is uniformly distributed over characteristic crystal-chemical positions of iron ions. The blocking temperatures of ferrihydrite nanoparticles have been determined. The nanoparticle sizes, magnetizations, surface anisotropy constants, and bulk anisotropy constants have been estimated. The doping of ferrihydrite nanoparticles with cobalt leads to a significant increase in the anisotropy constant of a nanoparticle and to the formation of surface rotational anisotropy with the surface anisotropy constant Ku = 1.6 × 10–3 erg/cm2.
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Varnakov S. N., Komogortsev S. V., Ovchinnikov S. G., Bartolome J., Sese J.
Заглавие : Magnetic properties and nonmagnetic phases formation in (Fe/Si)(n) films
Коллективы :
Разночтения заглавия :авие SCOPUS: Magnetic properties and nonmagnetic phases formation in (Fe/Si) n films
Место публикации : J. Appl. Phys.: AMER INST PHYSICS, 2008. - Vol. 104, Is. 9. - Ст.94703. - ISSN 0021-8979, DOI 10.1063/1.3005973
Примечания : Cited References: 23. - This work was supported by the Russian Academy of Science program "Spintronics," the complex integration project of the Siberian Branch of the Russian Academy of Science. 3.5, the Russian Foundation for Basic Research (Grant No. 07-03-00320), the "Ramon y Cajal" program, and Project No. MAT 2005/01272 of the Spanish Ministry of Education and Science.
Предметные рубрики: FE/SI/FE TRILAYER FILMS
GIANT MAGNETORESISTANCE
ULTRAHIGH-VACUUM
SUPERLATTICES
MULTILAYERS
EXCHANGE
Ключевые слова (''Своб.индексиров.''): activation energy--integral equations--magnetic properties--magnetization--magnets--multilayers--rate constants--silicon--thermal evaporation--vacuum--vacuum evaporation--fe layers--high temperatures--interface layers--irreversible behaviors--kinetic equations--n films--nonmagnetic--nonmagnetic phases--prefactor--quantitative analysis--rate equations--synthetic procedures--temperature dependences--ultrahigh-vacuum systems--phase interfaces
Аннотация: The magnetization of Fe/Si multilayers, grown by thermal evaporation in an ultrahigh vacuum system, was investigated at high temperatures. Magnetization and its temperature dependence up to a high temperature of 800 K depend on individual Fe layer thickness d(Fe). This dependence is the result of the formation of an Fe-Si interface layer (nonmagnetic phase) during the synthetic procedure. The fraction of this Fe-Si nonmagnetic phase is estimated versus dFe. At temperatures higher than 400 K an irreversible decrease in the magnetization occurs. A quantitative analysis of this irreversible behavior is proposed in terms of an exponential diffusion-like kinetic equation for the reaction that produces the Fe-Si nonmagnetic phase. The coefficients of the rate equation are the activation energy E(a) and the prefactor D(0), which have been determined for different d(Fe). (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3005973]
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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Komogortsev S. V., Iskhakov R. S., Balaev A. D., Kudashov A. G., Okotrub A. V., Smirnov S. I.
Заглавие : Magnetic properties of Fe3C ferromagnetic nanoparticles encapsulated in carbon nanotubes
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2007. - Vol. 49, Is. 4. - P734-738. - ISSN 1063-7834, DOI 10.1134/S1063783407040233
Примечания : Cited References: 15
Предметные рубрики: IRON NANOPARTICLES
EXCHANGE
SYSTEM
Аннотация: The low-temperature dependences of magnetic characteristics (namely, the coercive force H (c) , the remanent magnetization M (r) , local magnetic anisotropy fields H (a), and the saturation magnetization M (s) ) determined from the irreversible and reversible parts of the magnetization curves for Fe3C ferromagnetic nanoparticles encapsulated in carbon nanotubes are investigated experimentally. The behavior of the temperature dependences of the coercive force H (c) (T) and the remanent magnetization M (r) (T) indicates a single-domain structure of the particles under study and makes it possible to estimate their blocking temperature T (B) = 420-450 K. It is found that the saturation magnetization M (s) and the local magnetic anisotropy field H-a vary with temperature as similar to T-5/2.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Malakhovskii A. V., Sukhachev A. L., Vasil'ev A. D., Leont'ev A. A., Kartashev A. V., Temerov V. L., Gudim, I. A.
Заглавие : Nature of optical properties of GdFe3(BO3)4 and GdFe2.1Ga0.9(BO3)4 crystals and other 3d5 antiferromagnets
Место публикации : Eur. Phys. J. B: Springer, 2012. - Vol. 85, Is. 2. - P.80. - ISSN 1434-6028, DOI 10.1140/epjb/e2012-20953-1
Примечания : Cited References: 70. - The work was supported by the Russian Foundation for Basic Researches Grant 12-02-00026 and by Russian President Grant NSh-1044.2012.2.
Предметные рубрики: IRON BORATE GDFE3(BO3)4
D-D TRANSITIONS
EARTH FERROBORATES RFE3(BO3)4
ABSORPTION-SPECTRA
OCTAHEDRAL COMPLEXES
ELECTRONIC-STRUCTURE
NEEL TEMPERATURE
FINE-STRUCTURE
EXCHANGE
IONS
Аннотация: Influence of the partial substitution of paramagnetic Fe3+ ions by diamagnetic Ga3+ ions in the trigonal crystal GdFe3 (BO3)4 on its optical and magnetic properties is studied and discussed in connection with problems common for all antiferromagnets containing 3d 5 ions. Polarized optical absorption spectra and linear birefringence of GdFe3 (BO3)4 and GdFe2.1Ga0.9 (BO3)4 single crystals have been measured in the temperature range 85–293 K. Specific heat temperature dependence (2–300 K) and structure of GdFe2.1Ga0.9 (BO3)4 crystal have been also studied. As a result of substitution of 30% Fe to Ga the Neel temperature diminishes from 38 till 16 K, the strong absorption band edge shifts on 860 cm-1 (0.11 eV) to higher energy and the d-d transitions intensity decreases substantially larger than the Fe concentration does. Strong absorption band edge is shown to be due to Mott-Hubbard transitions. Correlation between position of the strong absorption band edge and the Neel temperature of antiferromagnets has been revealed. Properties of the doubly forbidden d-d transitions in the studied crystals and in other antiferromagnets are explained within the framework of the model of the exchange-vibronic pair absorption, which is theoretically analyzed in detail. The model permitted us to determine the connection between parameters of d-d absorption bands (intensity, width and their temperature dependences), on the one hand, and the exchange, spin-orbit and electron-lattice interactions, on the other hand.
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