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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Stolyar S. V., Bayukov O. A., Ladygina V. P., Ischenko L. A., Iskhakov R. S.
Заглавие : Structure and magnetic properties of biogenic ferrihydrite nanoparticles doped with gadolinium
Место публикации : J. Sib. Fed. Univ. Math. Phys. - 2013. - Vol. 6, Is. 3. - P.358-365. - ISSN 1997-1397; Журн. СФУ. Сер. "Математика и физика"
Ключевые слова (''Своб.индексиров.''): ferrihydrite nanoparticle--bacterial culture klebsiela oxytoca--mössbauer spectroscopy--gadolinium doping
Аннотация: Bacterial culture Klebsiella oxytoca was grown in a Lovley medium at various concentrations of gadolinium salt. Biogenic magnetic nanoparticles of ferrihydrite were investigated by Mossbauer spectroscopy and magnetization curves were obtained. The results of structural studies showed that iron Fe(5) takes new position when cultivating is carried out in medium with high concentrations of gadolinium. It was found that gadolinium is fit into the crystal structure of ferrihydrite. These results are consistent with the analysis of the magnetization curves.
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2.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Chubukov A. V., Maiti S., Korshunov M. A., Maier T., Hirschfeld P.J.
Заглавие : Evolution of symmetry and structure of the gap in Fe-based superconductors with doping and interactions
Коллективы : APS March Meeting (2012 ; 27 Feb.-2 March; Boston, Massachusetts, USA), American Physical Society March Meeting (2012 ; 27 Feb.-2 March; Boston, Massachusetts, USA)
Место публикации : Bull. Amer. Phys. Soc. - 2012. - Vol. 57, № 1. - P.316
Аннотация: We present a detailed study of the symmetry and structure of the pairing gap in Fe-based superconductors. We treat them as quasi-2D systems, decompose the pairing interaction into s− wave and d− wave channels and into contributions from scattering between different Fermi surfaces and analyze how each scattering evolves with doping and input parameters. We verify that each interaction is well approximated by the lowest angular harmonics and use this simplification to analyze the interplay between the interaction with and without spin-fluctuation components, the origin of the attraction in the s± and d x 2 −y 2 channels, the competition between them, the nature of angular dependence of the s± gaps along the electron Fermi surface, the conditions under which s± gap develops nodes, and the origin of superconductivity in heavily electron- or hole-doped systems, when only Fermi surfaces of one type are present. In particular, we find that with increased electron and hole doping, the competition from d− wave grows. In the case of strong hole doping, there is some ambiguity over the leading solution, but in the case of strong electron doping, d− wave emerges as clear winner.
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3.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Korshunov M. M.
Заглавие : Evolution of the Superconducting State of Fe-Based Compounds with Doping, Interactions, and Disorder
Коллективы : Ettore Majorana Foundation, Centre for Scientific Culture, Rome International Center for Materials Science, International School of Solid State Physics, "Phase separation and Superstripes in High Temperature Superconductors and Related Materials", Int. Conf. (55; 2012 ; July ; 11-17; Erice (Sicily), Italy)
Место публикации : International conferences «Phase separation and Superstripes in High Temperature Superconductors and Related Materials (Superstripes-2012)». - 2012. - P.39
Аннотация: We introduce an effective low-energy pairing model for Fe-based superconductors with s- and d-wave interaction components and a small number of input parameters and use it to study the doping evolution of the symmetry and the structure of the superconducting gap. We argue that the model describes the entire variety of pairing states found so far in the Fe-based superconductors and allows one to understand the mechanism of the attraction in s(±) and d(x(2)-y(2)) channels, the competition between s- and d-wave solutions, and the origin of superconductivity in heavily doped systems, when only electron or only hole pockets are present.
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Makarov I. A., Ovchinnikov S. G., Shneider E. I.
Заглавие : Dependence of the critical temperature of high-temperature cuprate superconductors on hoppings and spin correlations between CuO2 planes
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2012. - Vol. 114, Is. 2. - P.329-342. - ISSN 1063-7761, DOI 10.1134/S1063776112020264
Примечания : Cited References: 73. - This study was supported in part by the Presidium of the Russian Academy of Sciences (program "Quantum Physics of Condensed Media," project no. 18.7), jointly by the Siberian and Ural branches of the Russian Academy of Sciences (integration projects project no. 40), the Russian Foundation for Basic Research (project no. 09-02-00127), the Presidential Program in Support of Young Scientists in Russia (project no. MK-1683.2010.2), and the federal target program "Specialists" (project no. P891). One of the authors (E.I.Sh.) gratefully acknowledges support from the nonprofit Dynasty foundation.
Предметные рубрики: T-J MODEL
BAND HUBBARD-MODEL
SINGLE-CRYSTALS
TRANSITION-TEMPERATURE
FERMI-SURFACE
DOPING DEPENDENCE
THERMAL-EXPANSION
COPPER OXIDES
ANISOTROPY
LA2-XSRXCUO4
Аннотация: The influence of interlayer hoppings on the superconducting transition temperature (T c) in bilayer cuprates has been studied. The parameter of hopping between layers is expressed as t ⊥(k) = t ⊥(cos(k x ) − cos(k y ))2 and treated as a small perturbation for the states of two CuO2 planes described by the t-t′-t″-J* model. In the generalized mean field approximation for dx2−y2{d_{{x. } - {y. }}} symmetry of the superconducting gap, neither the interlayer hopping or exchange interaction, nor the pair hopping between CuO2 layers provides an additional mechanism of Cooper pair formation or an increase in T c. In the concentration dependence of T c, the bilayer splitting of the upper Hubbard band of quasi-holes is manifested as two peaks with temperatures slightly lower than the maximum T c for a single-layer cuprate. Interlayer antiferromagnetic spin correlations suppress bilayer splitting.
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Nikolaev S. V., Ovchinnikov S. G.
Заглавие : Effect of hole doping on the electronic structure and the Fermi surface in the Hubbard model within norm-conserving cluster pertubation theory
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2012. - Vol. 114, Is. 1. - P.118-131. - ISSN 1063-7761, DOI 10.1134/S1063776111150143
Примечания : Cited References: 51. - This study was supported financially by the Russian Foundation for Basic Research (project nos. 10-02-90725-mob_st and 09-02-00127), Program 18.7 of the Presidium of the Russian Academy of Sciences, the Federal Target Program "Personnel" (state contract no. P891), and the integrated project no. 40 of the Siberian Branch of the Russian Academy of Sciences.
Предметные рубрики: HIGH-TEMPERATURE SUPERCONDUCTORS
NARROW ENERGY-BANDS
CORRELATED ELECTRONS
PSEUDOGAP
EVOLUTION
La2-XSRXCuO4
INSULATOR
Аннотация: The concentration dependences of the band structure, spectral weight, density of states, and Fermi surface in the paramagnetic state are studied in the Hubbard model within cluster pertubation theory with 2 x 2 clusters. Representation of the Hubbard X operators makes it possible to control conservation of the spectral weight in constructing cluster perturbation theory. The calculated value of the ground-state energy is in good agreement with the results obtained using nonperturbative methods such as the quantum Monte Carlo method, exact diagonalization of a 4 x 4 cluster, and the variational Monte Carlo method. It is shown that in the case of hole doping, the states in the band gap (in-gap states) lie near the top of the lower Hubbard band for large values of U and near the bottom of the upper band for small U. The concentration dependence of the Fermi surface strongly depends on hopping to second (t') and third (t '') neighbors. For parameter values typical of HTSC cuprates, the existence of three concentration regions with different Fermi surfaces is demonstrated. It is shown that broadening of the spectral electron density with an energy resolution typical of contemporary ARPES leads to a pattern of arcs with a length depending on the concentration. Only an order-of-magnitude decrease in the linewidth makes it possible to obtain the true Fermi surface from the spectral density. The kinks associated with strong electron correlations are detected in the dispersion relation below the Fermi level.
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Korovushkin M. M.
Заглавие : Lower subband splitting and superconductivity of 2D Hubbard fermions with strong intersite correlations
Коллективы : International Symposium "Nanophysics and Nanoelectronics-2011" (March 2011; Nizhni Novgorod)
Место публикации : Bull. Russ. Acad. Sci. Phys.: Allerton Press, 2012. - Vol. 76, Is. 2. - P.133-135. - ISSN 1062-8738, DOI 10.3103/S1062873812020074
Примечания : Cited References: 6. - This study was supported by Quantum Physics of Condensed Matter program of the Presidium of the Russian Academy of Sciences; the Russian Foundation for Basic Research, project np. 10-02-00251; the federal target program Scientists and Science Teachers of an Innovate Russia, 2009-2013; the Siberian Branch of the Russian Academy of Sciences, complex integration project no. 53; RF Presidential Grant MK-1300.2011.2; and the Siberian Branch of the Russian Academy of Sciences' Lavrent'ev Competition for Young Scientists.
Ключевые слова (''Своб.индексиров.''): coulomb correlations--doping levels--electron structures--fermi state--hubbard--intersite correlation--mean-square fluctuations--spectral intensity--split-off band--subbands--natural sciences
Аннотация: The effect of the strong intersite Coulomb correlations on the formation of an electron structure in the Shubin-Vonsowsky model in the regime of strong one-site correlations is studied. The results reveal a split-off band of the Fermi states. The spectral intensity of this band grows with the enhancement of the doping level and is determined by the mean-square fluctuation of occupation numbers. This changes the structure of the electron density of states qualitatively. © 2012 Allerton Press, Inc.
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kuklin A. V., Kuzubov A. A., Krasnov P. O., Lykhin A. O., Tikhonova L. V.
Заглавие : Ni-doping effect of Mg(0 0 0 1) surface to use it as a hydrogen storage material
Место публикации : J. Alloys Compd.: Elsevier Science, 2014. - Vol. 609. - P.93-99. - ISSN 0925-8388, DOI 10.1016/j.jallcom.2014.04.160. - ISSN 1873-4669
Примечания : Cited References: 38
Предметные рубрики: INITIO MOLECULAR-DYNAMICS
AUGMENTED-WAVE METHOD
MINIMUM ENERGY PATHS
ELASTIC BAND METHOD
METAL-HYDRIDES
SADDLE-POINTS
MAGNESIUM
Mg
TRANSITION
Pd
Ключевые слова (''Своб.индексиров.''): hydrogen absorbing materials--intermetallics--diffusion--dft--mg-based hydride
Аннотация: A detailed study of Ni-doped Mg(0 0 0 1) surface performed by PAW method and the gradient corrected density functional GGA-PBE within the framework of generalized Kohn–Sham density functional theory (DFT) is presented in this work. Structural and electronic properties of magnesium surface interaction with nickel for the purpose of such compounds use for creation of hydrogen storage matrixes were investigated here. Choice of the PBE functional was caused by the good accordance of its prediction of the cell parameters with experimental results. It was shown that Ni atoms prefer to substitute for Mg atoms. Using NEB method, the diffusion barrier was calculated, and the most probable reaction path was established. In particular, when the Ni atom dopes the magnesium surface, it can migrate to the bulk and substitute for Mg in subsurface layers. Also a possibility of nickel cluster formation on clean surface of magnesium was examined. The kinetic factors hinder the movement of the nickel atoms to each other and make problematic the formation of clusters. The studies presented here showed that the diffusion barriers of the nickel atom migration from the cluster on the surface to the bulk of magnesium are 1.179 eV and 1.211 eV for the forward and reverse reactions, respectively. Therefore an improvement of the hydrogenation properties of Ni-doped magnesium surface depends on deposition not of the individual atoms, but their clusters. Hydrogenation of Ni cluster doping the magnesium surface was investigated. Initially Kubas complexes arise on the Ni cluster with hydrogen–hydrogen bond lengths equal to 0.80–0.87 Å. Next the cluster needs to be saturated by hydrogen atoms to allow them later to migrate from cluster to magnesium.
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8.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Udod L. V., Aplesnin S. S., Eremin E. V., Sitnikov M. N., Molokeev M. S.
Заглавие : Effect of Mn doping on magnetic and dielectric properties of Bi2Sn2O7
Коллективы : Moscow International Symposium on Magnetism
Место публикации : Moscow Int. Symp. on Magnet. (MISM-2014): Book of abstracts. - 2014. - Ст.1PO-J1-6. - P.513. - ISBN 978-5-91978-025-0
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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Udod L. V., Aplesnin S. S., Sitnikov M. N., Eremin E. V., Molokeev M. S.
Заглавие : Effect of Mn doping on magnetic and dielectric properties of Bi2Sn2O7
Коллективы : Moscow International Symposium on Magnetism
Место публикации : Solid State Phenom.: Selected, peer reviewed papers/ ed.: N. Perov, A. Semisalova: Trans Tech Publications Ltd, 2015. - Vol. 233-234: Achievements in Magnetism. - P.105-108. - ISSN 1662-9779, DOI 10.4028/www.scientific.net/SSP.233-234.105. - ISSN 978-3-03835-482-6
Предметные рубрики: Achievements in magnetism
Ключевые слова (''Своб.индексиров.''): crystallographic structure--cubic phase--dielectric permeability--electrical resistivity--magnetic moment--martensitic phase transitions--orthorhombic phases--polymorphic transformation
Аннотация: The Bi2(Sn0.95Mn0.05)2O7 compound existing simultaneously in two polymorphic modifications, namely, orthorhombic and cubic has been synthesized for the first time by solid-phase synthesis. The magnetic, dielectric and electrical properties of the compound have been studied. Anomalies in the temperature dependences of the electrical resistance and magnetic propoties have been found. These features are explained as martensitic phase transitions.
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10.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Shneyder E. I., Korshunov M. M., Makarov I. A.
Заглавие : Doping dependent band structure and pairing in strongly correlated electron systems of high-Tc cuprates
Коллективы : International symposium on strong nonlinear vibronic and electronic interactions in solids
Место публикации : V International symposium on strong nonlinear vibronic and electronic interactions in solids: program, book of abstracts . - 2015. - Ст.O18. - P.28
Примечания : Библиогр.: 1 назв.
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