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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Safronov A. P., Beketov I. V., Komogortsev S. V., Kurlyandskaya G. V., Medvedev A. I., Leiman D. V., Larranaga A., Bhagat S. M.
Заглавие : Spherical magnetic nanoparticles fabricated by laser target evaporation
Место публикации : AIP Adv.: American Institute of Physics, 2013. - Vol. 3, Is. 5. - Ст.052135. - P. - ISSN 2158-3226, DOI 10.1063/1.4808368
Примечания : Cited References: 47. - This work was supported by the RFBR 10-02-96015 and 12-02-31385 projects, UrFU 215, Spanish MEC MAT2011-27573-C04 grants, Universidad del Pais Vasco UPV/EHU under UFI11/53 action and Physics Department of the University of Maryland visiting grant. Selected measurements were performed at SGIker service of UPV-EHU. We thank O.M. Samatov, Dr. A.M. Murzakayev, Dr. I. Orue, and A.A. Svalova for special support.
Предметные рубрики: IRON-OXIDE NANOPOWDERS
CO2-LASER EVAPORATION
FE3O4 NANOPARTICLES
FINITE-SIZE
TEMPERATURE
FERROMAGNETS
FERROFLUIDS
DEPENDENCE
EXPLOSION
PARTICLES
Аннотация: Magnetic nanoparticles of iron oxide (MNPs) were prepared by the laser target evaporation technique (LTE). The main focus was on the fabrication of de-aggregated spherical maghemite MNPs with a narrow size distribution and enhanced effective magnetization. X-ray diffraction, transmission electron microscopy, magnetization and microwave absorption measurements were comparatively analyzed. The shape of the MNPs (mean diameter of 9 nm) was very close to being spherical. The lattice constant of the crystalline phase was substantially smaller than that of stoichiometric magnetite but larger than the lattice constant of maghemite. High value of M-s up to 300 K was established. The 300 K ferromagnetic resonance signal is a single line located at a field expected from spherical magnetic particles with negligible magnetic anisotropy. The maximum obtained concentration of water based ferrofluid was as high as 10g/l of magnetic material. In order to understand the temperature and field dependence of MNPs magnetization, we invoke the core-shell model. The nanoparticles is said to have a ferrimagnetic core (roughly 70 percent of the caliper size) while the shell consists of surface layers in which the spins are frozen having no long range magnetic order. The core-shell interactions were estimated in frame of random anisotropy model. The obtained assembly of de-aggregated nanoparticles is an example of magnetic nanofluid stable under ambient conditions even without an electrostatic stabilizer. (C) 2013 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Edelman I. S., Ivanova O. S., Ivantsov R. D., Velikanov D. A., Zabluda V. N., Zubavichus Y., Veligzhanin A. A., Zaikovskiy V. I., Stepanov S., Artemenko A., Curely J., Kliava J.
Заглавие : Magnetic nanoparticles formed in glasses co-doped with iron and larger radius elements
Место публикации : J. Appl. Phys.: American Institute of Physics, 2012. - Vol. 112, Is. 8. - Ст.84331. - P. - ISSN 0021-8979, DOI 10.1063/1.4759244
Примечания : Cited References: 65. - This work was partly supported by the Russian Foundation for Basic Research, Grant Nos. 07-02-92174 RFBR-CNRS and 11-02-00972, and President of Russia Federation Grant No NSh 1044.2012.2. A. Artemenko acknowledges financial support from the Marie Curie International Incoming Fellowship within the 7th European Community Framework Programme (EPREXINA, GA 255662). The synchrotron measurements were supported via the Russian federal Contract No. 16.552.11.7003. The authors thank K. P. Polyakova for the preparation of thin films.
Предметные рубрики: SUPERPARAMAGNETIC RESONANCE
FERROMAGNETIC-RESONANCE
TEMPERATURE-DEPENDENCE
FERRITE NANOPARTICLES
OXIDE NANOPARTICLES
FARADAY-ROTATION
CERAMICS
ANISOTROPY
PARTICLES
SPECTRA
Аннотация: A new type of nanoparticle-containing glasses based on borate glasses co-doped with low contents of iron and larger radius elements, Dy, Tb, Gd, Ho, Er, Y, and Bi, is studied. Heat treatment of these glasses results in formation of magnetic nanoparticles, radically changing their physical properties. Transmission electron microscopy and synchrotron radiation-based techniques: x-ray diffraction, extended x-ray absorption fine structure, x-ray absorption near-edge structure, and small-angle x-ray scattering, show a broad distribution of nanoparticle sizes with characteristics depending on the treatment regime; a crystalline structure of these nanoparticles is detected in heat treated samples. Magnetic circular dichroism (MCD) studies of samples subjected to heat treatment as well as of maghemite, magnetite, and iron garnet allow to unambiguously assign the nanoparticle structure to maghemite, independently of co-dopant nature and of heat treatment regime used. Different features observed in the MCD spectra are related to different electron transitions in Fe3+ ions gathered in the nanoparticles. The static magnetization in heat treated samples has non-linear dependence on the magnetizing field with hysteresis. Zero-field cooled magnetization curves show that at higher temperatures the nanoparticles occur in superparamagnetic state with blocking temperatures above 100 K. Below ca. 20 K, a considerable contribution to both zero field-cooled and field-cooled magnetizations occurs from diluted paramagnetic ions. Variable-temperature electron magnetic resonance (EMR) studies unambiguously show that in as-prepared glasses paramagnetic ions are in diluted state and confirm the formation of magnetic nanoparticles already at earlier stages of heat treatment. Computer simulations of the EMR spectra corroborate the broad distribution of nanoparticle sizes found by "direct" techniques as well as superparamagnetic nanoparticle behaviour demonstrated in the magnetization studies. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4759244]
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kagan M. Y., Efremov D. V., Mar'enko M. S., Val'kov V. V.
Заглавие : Superconductivity in repulsive fermi-systems at low density
Коллективы : RFBR [11-02-00741]
Место публикации : J. Supercond. Nov. Magn.: SPRINGER, 2013. - Vol. 26, Is. 9. - P.2809-2815. - ISSN 1557-1939, DOI 10.1007/s10948-013-2262-9
Примечания : Cited References: 57. - The authors acknowledge helpful discussions with A. V. Chubukov, A. S. Alexandrov, V. V. Kabanov, K. I. Kugel, Yu. V. Kopaev, N.M. Plakida, N.V. Prokof'ev, M. M. Korovushkin, M. A. Mitskan. M. Yu. K. work was supported by RFBR grant No. 11-02-00741.
Предметные рубрики: T-J MODEL
SUPERFLUID TRANSITION-TEMPERATURE
FRACTIONAL-STATISTICS
PHASE-SEPARATION
HUBBARD-MODEL
GAS
ENHANCEMENT
MECHANISM
EXCHANGE
PARTICLES
Ключевые слова (''Своб.индексиров.''): anomalous superconductivity--p-wave and d-wave pairings--kohn-luttinger mechanism--shubin-vonsovsky--hubbard and t-j models
Аннотация: In the large variety of models such as 3D and 2D Fermi-gas model with hard-core repulsion, 3D and 2D Hubbard model, and the Shubin-Vonsovsky model, we demonstrate the possibility of triplet p-wave pairing at low electron density. We show that the critical temperature of the p-wave pairing can be strongly increased in a spin-polarized case or in a two-band situation already at low density and reach experimentally feasible values of (1-5) K. We also discuss briefly d-wave pairing and high-T-C superconductivity with T-C similar to 100 K, which arises in the 2D t-J model in the range of parameters realistic for cuprates.
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ershov A. E., Isaev I. L., Semina P. N., Markel V. A., Karpov S. V.
Заглавие : Effects of size polydispersity on the extinction spectra of colloidal nanoparticle aggregates
Место публикации : Phys. Rev. B: American Physical Society, 2012. - Vol. 85, Is. 4. - Ст.045421. - P. - ISSN 1098-0121, DOI 10.1103/PhysRevB.85.045421
Примечания : Cited References: 41. - This work was supported by grants from the following foundations of the Russian Federation: Presidium of RAS, OFN RAS, and SB RAS.
Предметные рубрики: METAL FRACTAL CLUSTERS
OPTICAL-PROPERTIES
ABSORPTION
NONLINEARITIES
COMPOSITES
SCATTERING
PARTICLES
SPHERES
GRAINS
Аннотация: We investigate the effect of particle polydispersity on the optical extinction spectra of colloidal aggregates of spherical metallic (silver) nanoparticles, taking into account the realistic interparticle gaps caused by layers of stabilizing polymer adsorbed on the metal surface (adlayers). The spectra of computer-generated aggregates are computed using two different methods. The coupled-multipole method is used in the quasistatic approximation and the coupled-dipole method beyond the quasistatics. The latter approach is applicable if the interparticle gaps are sufficiently wide relative to the particle radii. Simulations are performed for two different particle size distribution functions (bimodal and Gaussian), varying the number of particles per aggregate, and different distribution functions of the interparticle gap width. The strong influence of the latter factor on the spectra is demonstrated and investigated in detail.
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Karpov S. V., Semina P. N., Gavrilyuk A. P.
Заглавие : The role of the electron tunneling effect in the coagulation kinetics of polydisperse metal nanocolloids
Место публикации : Colloid J.: MAIK Nauka-Interperiodica / Springer, 2012. - Vol. 74, Is. 3. - P.305-312. - ISSN 1061-933X, DOI 10.1134/S1061933X12030052
Примечания : Cited References: 16. - Authors are thankful to G. A. Chiganova for discussions and helpful comments. Studies were carried out with the support of grants: the Presidium of RAS No 29 and No 31, OFN RAS III.9.5, IP SB RAS No 43, IP SB RAS (and SFU) No 101.
Предметные рубрики: PARTICLES
Аннотация: The energy of pair interactions between metal nanoparticles of different sizes is shown to be able to increase upon coagulation due to the additional electrostatic effect resulting from mutual heteropolar charging of the particles. The tunnel electron transfer occurring upon the collisions between particles of different sizes may be the reason for the charging. The transfer is caused by the dependence of the electron work function on the particle size. The electron transfer through the interparticle gap equalizes the Fermi levels in particles of different sizes and is associated with this dependence. Using the example of bimodal silver nanocolloids, it is shown that mutual heteropolar charging of particles with different sizes may accelerate the coagulation of polydisperse colloidal systems by an order of magnitude or more as compared with monodisperse systems, in which this effect is absent.
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Atuchin V. V., Bekenev V. L., Chimitova O. D., Molokeev M. S., Bazarov B. G., Bazarova J. G., Khuzhum O. Y., Lim C. S.
Заглавие : Synthesis and electronic properties of β-RbNd(MoO4)2
Место публикации : Asian J. Chem. - 2014. - Vol. 26, No. 5. - P.1284-1286. - ISSN 0970-7077, DOI 10.14233/ajchem.2014.17209
Примечания : Cited References: 26. - This study is partly supported by by the Ministry of Education and Science of the Russian Federation.
Предметные рубрики: UP-CONVERSION PHOTOLUMINESCENCE
VIBRATIONAL PROPERTIES
CRYSTAL-STRUCTURE
PARTICLES
MOLYBDATE
SPECTROSCOPY
SYSTEM
ER3+
Ключевые слова (''Своб.индексиров.''): β-rbnd(moo4)2--electronic structure--ab initio calculations--x-ray photoelectron spectroscopy
Аннотация: The electronic structure of β-RbNd(MoO4)2 has been evaluated from experimental and theoretical points of view. For the molybdate, X-ray photoelectron valence-band spectra have been measured. The total and partial densities of states of the constituent atoms of β-RbNd(MoO4)2 have been calculated using the FP-LAPW method. The FP-LAPW data reveal that main contributors in the valence-band region of β-RbNd(MoO4)2 are the Rb 4p-, Nd 4f-, Mo 4d- and O 2p-like states.
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kirillov V. L., Balaev D. A., Semenov S. V., Shaikhutdinov K. A., Martyanov O. N.
Заглавие : Size control in the formation of magnetite nanoparticles in the presence of citrate ions
Коллективы : Siberian Branch of the Russian Academy of Sciences
Место публикации : Mater. Chem. Phys.: Elsevier Science, 2014. - Vol. 145, Is. 1-2. - P.75-81. - ISSN 0254-0584, DOI 10.1016/j.matchemphys.2014.01.036. - ISSN 1879-3312
Примечания : Cited References: 46. - This work was supported by the Interdisciplinary Integration Project no. 45 of the Siberian Branch of the Russian Academy of Sciences for 2012-2014.
Предметные рубрики: OLEIC-ACID
CATALYST
HYPERTHERMIA
PARTICLES
OXIDATION
REMOVAL
CO
Ключевые слова (''Своб.индексиров.''): magnetic materials--magnetic properties--precipitation--electron paramagnetic resonance
Аннотация: A one-pot synthesis method for the controllable growth of magnetite nanoparticles directly during the process of co-precipitation using citrate ions was developed. The effects of the concentration of citrate ions and the solution pH on the characteristics of magnetite particles with sizes in the range of 4-10 nm synthesized by the method of co-precipitation were studied. The results showed that the specified concentration of citrate ions allowed the preparation of magnetite particles with a definite size that exhibited superparamagnetic behaviour in a particular temperature range. As the concentration ratio of citrate to iron ions was increased from 0 to 0.11, the average size of the prepared magnetite particles decreased from 10.5 to 4.4 nm. As a result, the superparamagnetic blocking temperature decreased from 300 to 20 K, the saturation magnetisation decreased from 50 to 20 emu g(-1), and the average magnetic moment decreased from 8000 mu(B) to 340 mu(B) (at T = 300 K). The obtained experimental data proved that the size effects of the magnetite nanoparticles can be attributed to the capping of the magnetite surface by adsorbed citrate ions. Thus, the suggested approach allows magnetite nanoparticles to be prepared with an optimum particle size around superparamagnetic threshold that prevents their irreversible agglomeration and simultaneously allows them to be removed from a solution at an acceptable rate. (C) 2014 Elsevier B.V. All rights reserved.
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pankrats A. I., Vorotynov A. M., Tugarinov V. I., Zharkov S. M., Velikanov D. A., Abramova G. M., Zeer G. M., Ramasamy K., Gupta A.
Заглавие : Structural and magnetic resonance investigations of CuCr2S4 nanoclusters and nanocrystals
Коллективы : Grant CRDF-SB RAS "New Nano-size and Layered Cu-containing Sulphides for Electronics" [RUP1-7054-KR-11, 16854]; Ministry of education and science of the Russian Federation
Место публикации : J. Appl. Phys.: American Institute of Physics, 2014. - Vol. 116, Is. 5. - Ст.54302. - ISSN 0021-8979, DOI 10.1063/1.4891993. - ISSN 1089-7550
Примечания : Cited References: 26. - The work was supported by a Grant CRDF-SB RAS "New Nano-size and Layered Cu-containing Sulphides for Electronics" RUP1-7054-KR-11, N 16854. S.M.Z. acknowledges support from the Ministry of education and science of the Russian Federation (in the framework of the state assignment for SFU for 2014).
Предметные рубрики: SUPERPARAMAGNETIC RESONANCE
NANOPARTICLES
GLASS
BIOMEDICINE
PARTICLES
SPINELS
Аннотация: Nanoclusters and nanocrystals of the room temperature magnetic spinel CuCr2S4 synthesized using a facile solution-based method have been examined by transmission electron microscopy, magnetic measurements, and magnetic resonance over a wide frequency range 9.6–80 GHz and at temperatures down to 4.2 K. Decreasing of the resonance field and broadening of the resonance lines below 50 K for both samples are due to the freezing of magnetic moments of nanocubes and nanocrystalline particles constituting nanoclusters. The effective fields of averaged magnetic anisotropy (HA)≌2.4 kOe are similar for both nanopowder samples as estimated from resonance measurements at T = 4.2 K. An additional blocking temperature T b ≅ 300 K appears in nanoclusters due to freezing of the magnetic moment of the entire cluster as a whole. Below this blocking temperature, the magnetic dipolar field acting in boundary areas of interacting constituent nanocrystals is responsible for the additional low-field resonance line observed in the resonance spectra of nanoclusters at X-band.
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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Slabko V. V., Tsipotan A. S. , Aleksandrovsky A. S., Slyusareva E. A.
Заглавие : Dynamics of self-organized aggregation of resonant nanoparticles in a laser field
Коллективы : Grant of the Ministry of Education and Science of the Russian Federation for Siberian Federal University; SB RAS Grant [24.31]; RFBR [14-02-00219 A]
Место публикации : Appl. Phys. B: Springer, 2014. - Vol. 117, Is. 1. - P.271-278. - ISSN 0946-2171, DOI 10.1007/s00340-014-5831-0. - ISSN 1432-0649
Примечания : Cited References: 30. - This research is partially supported by Grant of the Ministry of Education and Science of the Russian Federation for Siberian Federal University, by SB RAS Grant 24.31, and by RFBR Research Project No. 14-02-00219 A.
Предметные рубрики: PHOTOSTIMULATED AGGREGATION
SILVER
PRINCIPLES
PARTICLES
SPECTRA
SOLS
Аннотация: Self-organized aggregation of nanoparticles in external resonant laser field is considered using Brownian dynamics model. Formation probabilities are calculated for the pair of particles in dependence on laser wavelength and mutual orientation of particles. Times required for aggregation are calculated. Possibility of efficient aggregation using pulsed laser is deduced.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Morozov E. V., Shabanova O. V., Falaleev O. V.
Заглавие : MRI Comparative Study of Container Geometry Impact on the PMMA Spheres Sedimentation
Место публикации : Appl. Magn. Reson. - 2013. - Vol. 44, Is. 5. - P.619-636. - ISSN 0937-9347, DOI 10.1007/s00723-012-0432-8
Примечания : Cited References: 31
Предметные рубрики: OPAL PHOTONIC CRYSTALS
SUSPENSIONS
PARTICLES
VELOCITY
Аннотация: Nuclear magnetic resonance (NMR) imaging results are presented for the comparative study of sedimentation of the polymethylmethacrylate colloidal suspensions with spherical particle diameters of 475, 350 and 255 nm. The time evolution of the particle volume fraction in the sedimenting system, velocity of the fluid/suspension interface, interface broadening, and sediment growth velocity are measured against the system concentration as well as the container geometry. Using the experimental data the hindered settling function is evaluated. The influence of the container geometry on the parameters defining the hindered settling function in different approaches is evaluated for the first time. The limiting value of the particle diameter is estimated at which the container geometry has no impact any longer. This effect can be explained by the microscale structure persisting at low Peclet numbers. In addition, the influence of the container geometry on interface broadening and sediment formation for different particle diameters and volume fractions is studied. Spontaneous sediment packing induced by a modified container geometry has been found. NMR imaging has proven to be a highly efficient research tool for studying sedimentation at low Peclet numbers.
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