Author
S. V. Komogortsev
Other affiliations: Siberian State Aerospace University, Siberian Federal University, Siberian State Technological University
Bio: S. V. Komogortsev is an academic researcher from Russian Academy of Sciences. The author has contributed to research in topics: Magnetic anisotropy & Magnetization. The author has an hindex of 14, co-authored 92 publications receiving 736 citations. Previous affiliations of S. V. Komogortsev include Siberian State Aerospace University & Siberian Federal University.
Papers published on a yearly basis
Papers
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TL;DR: In this paper, the 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.
Abstract: 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.
87 citations
TL;DR: In this article, the magnetic microstructure of nanostructured ferromagnets is represented by an ensemble of stochastic magnetic domains, regions with dimensions of the length of magnetic orientation coherency.
Abstract: The magnetic microstructure of nanostructured ferromagnets is represented by an ensemble of stochastic magnetic domains—regions with dimensions of the length of magnetic orientation coherency. It is shown that the curves displaying the approach of magnetization to saturation make it possible to determine the dimension of the element of the micromagnetic structure, i.e., the size of the stochastic domain and the constant of the effective anisotropy in this element, the size of the element of the nanostructure and the constant its local anisotropy, as well as the dimensionality of the exchange-coupled ferromagnetic nanoparticles.
56 citations
TL;DR: In this article, a new law of the approach to magnetic saturation is proposed based on scaling in ferromagnets with random magnetic anisotropy, which is consistent with the known laws derived within perturbation theory in extreme cases, but it describes the transition mode between power-low asymptotic regimes better.
42 citations
TL;DR: In this paper, the authors investigated the low-temperature dependences of magnetic characteristics (namely, the coercive force, the remanent magnetization, local magnetic anisotropy fields, and saturation magnetization) determined from the irreversible and reversible parts of the magnetization curves for Fe3C ferromagnetic nanoparticles encapsulated in carbon nanotubes.
Abstract: 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 ∼T
5/2
36 citations
TL;DR: The magnetic microstructure of Co-Ni binary alloy nanowires can be represented as an ensemble of stochastic magnetic domains whose size is determined by the magnetic correlation length as discussed by the authors.
33 citations
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TL;DR: In this article, the results of recent experimental and theoretical studies of well characterized epitaxial structures based on Fe, Co and Ni to illustrate how intrinsic fundamental properties such as the magnetic exchange interactions, magnetic moment and magnetic anisotropies change markedly in ultrathin films as compared with their bulk counterparts, and to emphasize the role of atomic scale structure, strain and crystallinity in determining the magnetic properties.
Abstract: In this paper, we review some of the key concepts in ultrathin film magnetism which underpin nanomagnetism. We survey the results of recent experimental and theoretical studies of well characterized epitaxial structures based on Fe, Co and Ni to illustrate how intrinsic fundamental properties such as the magnetic exchange interactions, magnetic moment and magnetic anisotropies change markedly in ultrathin films as compared with their bulk counterparts, and to emphasize the role of atomic scale structure, strain and crystallinity in determining the magnetic properties. After introducing the key length scales in magnetism, we describe the 2D magnetic phase transition and survey studies of the thickness dependent Curie temperature and the critical exponents which characterize the paramagnetic–ferromagnetic phase transition. We next discuss recent experimental and theoretical results on the determination of the exchange constant, followed by an overview of measurements of the magnetic moment in the elemental 3d transition metal thin films in the various crystal phases that have been successfully stabilized, thereby illustrating the sensitivity of the magnetic moment to the local symmetry and to the atomic environment. Finally, we discuss briefly the magnetic anisotropies of Fe, Co and Ni in the fcc crystalline phase, to emphasize the role of structure and the details of the interface in influencing the magnetic properties. The dramatic effect that adsorbates can have on the magnetic anisotropies of thin magnetic films is also discussed. Our survey demonstrates that the fundamental properties, namely, the magnetic moment and magnetic anisotropies of ultrathin films have dramatically different behaviour compared with those of the bulk while the comparable size of the structural and magnetic contributions to the total energy of ultrathin structures results in an exquisitely sensitive dependence of the magnetic properties on the film structure.
516 citations
501 citations
TL;DR: In this paper, aniline molecules were grafted onto multiwalled carbon nanotubes (MWCNTs) by using a plasma-induced grafting technique, and the polyaniline (PANI) grafted MWCNTs were characterized by using ultraviolet−visible spectrophotometry, X-ray photoelectron spectroscopy, Raman spectrograph, thermogravimetric analysis−differential thermal analysis, and field-emission scanning electron microscopy.
Abstract: Aniline molecules were grafted onto multiwalled carbon nanotubes (MWCNTs) by using a plasma-induced grafting technique. The polyaniline (PANI) grafted MWCNTs (PANI/MWCNTs) were characterized by using ultraviolet−visible spectrophotometry, X-ray photoelectron spectroscopy, Raman spectroscopy, thermogravimetric analysis−differential thermal analysis, and field-emission scanning electron microscopy. The results indicated that the magnetic composite consisting of PANI/MWCNTs was synthesized. The application of PANI/MWCNTs for the removal of aniline and phenol from aqueous solutions was investigated under ambient conditions. The grafted PANI on MWCNTs contributed to the enhancement of the adsorption capacity because of the strong conjugate effect between PANI and organic pollutants. PANI/MWCNTs can be separated and recovered from aqueous solution by magnetic separation. The results show that PANI/MWCNTs are a promising magnetic material for the preconcentration and separation of organic pollutants from large v...
166 citations
TL;DR: In this paper, a core-shell Fe3O4@polypyrrole composite microspheres have been successfully prepared via chemical oxidative polymerization in the presence of poly(vinyl alcohol) and p-toluenesulfonic acid.
Abstract: Highly regulated core–shell Fe3O4@polypyrrole composite microspheres have been successfully prepared via chemical oxidative polymerization in the presence of poly(vinyl alcohol) and p-toluenesulfonic acid. The polypyrrole shell thickness can be adjusted from 20 to 80 nm with the variation of the pyrrole/Fe3O4 ratio. Investigations of the microwave absorbing properties indicate that the polypyrrole shell plays an important role, and the maximum reflection loss of composite microspheres can reach as much as −31.5 dB (>99.9% absorption) at 15.5 GHz with a matching layer thickness of 2.5 mm. Compared to the physically blended Fe3O4–PPy composites, Fe3O4@polypyrrole composite microspheres not only possess better reflection loss performance but also have a wider absorbing bandwidth of 5.2 GHz (12.8–18 GHz) in the Ku band, which may be attributed to the intensive synergistic effect of dielectric loss from polypyrrole shells and magnetic loss from Fe3O4 cores. Therefore, regulated core–shell Fe3O4@polypyrrole com...
131 citations
TL;DR: One-dimensional (1D) heterostructures of uniform CdS nanowires separately decorated with hematite (α-Fe2O3) nanoparticles or magnetite (Fe3O4) microspheres were successfully synthesized via a two-step solvothermal deposition method as mentioned in this paper.
Abstract: One-dimensional (1D) heterostructures of uniform CdS nanowires separately decorated with hematite (α-Fe2O3) nanoparticles or magnetite (Fe3O4) microspheres were successfully synthesized via a two-step solvothermal deposition method. Each CdS nanowire had a uniform diameter of 40−50 nm and a length ranging from several to several tens of micrometers. Quasicubic α-Fe2O3 nanoparticles, with edge lengths up to about 30 nm, and Fe3O4 microspheres, with diameters of about 200 nm, anchored on nanowires free from any surface pretreatment form 1D dimer-type CdS/α-Fe2O3 semiconductor heterostructures or CdS/Fe3O4 semiconductor magnetic functionally assembled heterostructures. It was also found that α-Fe2O3 nanoparticles with a smooth surface were well-crystallized, and Fe3O4 microspheres with a relatively rough surface showed a polycrystalline nature. The relationship between the crystal structures and effects of lattice mismatch on the formation of heterojunctions were systematically investigated. The magnetic and...
125 citations