Leonid Afremov, S. V. Anisimov, Ilia G. Iliushin,
In this work, a model of interacting two-phase core/shell nanoparticles is presented. An analysis of the effect of exchange coupling, size and magnetic interaction between Fe/Fe3O4 nanoparticles on the coercive field Hc, the remanent saturation magnetisation Mrs and the saturation magnetisation Ms has been carried out. We show that the hysteresis characteristics grow together with the size of nanoparticles. Changing the exchange interaction constant leads to a nonmonotonic change of Hc and Mrs. ...
Tópico(s): Theoretical and Computational Physics
2017 - Elsevier BV | Journal of Magnetism and Magnetic Materials
Leonid Afremov, S. V. Anisimov, Ilia G. Iliushin,
A theoretical study was conducted on the size dependence of the blocking temperature Tb of a system of interacting core/shell nanoparticles. A method for estimating the blocking temperature of interacting core/shell nanoparticles is presented, which allows Tb to be calculated more precisely than using the "Neel relation". It was shown that with an increase in the intensity of the magnetostatic interaction (concentration of nanoparticles), the blocking temperature increases, while the growth of the ...
Tópico(s): nanoparticles nucleation surface interactions
2020 - Elsevier BV | Chinese Journal of Physics
Leonid Afremov, I. G. Il’yushin,
In terms of the two‐phase nanoparticles model, the effect of mechanical stress on the magnetic state of both uniaxial and multiaxial heterophase magnetic is investigated. The spectrum of critical fields of reversal of phases′ magnetic moments was calculated and phase diagrams were drawn to assess the effect of mechanical stress on the degree of metastability of two‐phase nanoparticles′ magnetic states. By the example of epitaxial cobalt‐coated γ ‐Fe 2 O 3 particles, a theoretical analysis of the ...
Tópico(s): Magnetic Properties and Synthesis of Ferrites
2013 - Hindawi Publishing Corporation | Journal of Nanomaterials
S. V. Anisimov, Leonid Afremov, Alexander Petrov,
The effect of temperature and size on the exchange bias field of a hysteresis loop was studied based on the model of two-phase core/shell nanoparticles. Using the random interaction field method, the temperature dependence of the interfacial exchange interaction constant was estimated. It is shown that with increasing temperature, the field of exchange bias as well as the constant of interphase exchange interaction fall exponentially. An increase in the inverse size of nanoparticles leads to a linear ...
Tópico(s): nanoparticles nucleation surface interactions
2019 - Elsevier BV | Journal of Magnetism and Magnetic Materials
Leonid Afremov, I. G. Il’yushin,
Modeling study of magnetic and concentration phase transition in ultrathin films of diluted magnet has been carried out under approximation of random interaction between atomic magnetic moments of nearest neighbors and within the framework of Ising model. The dependence of Curie temperature on concentration of magnetic atoms was formed. It is shown that with increasing of thickness of ultrathin film the critical concentration of transition from unordered to ordered magnetic state decreases down ...
Tópico(s): Characterization and Applications of Magnetic Nanoparticles
2013 - Trans Tech Publications | Advanced materials research
Tópico(s): Thermoelastic and Magnetoelastic Phenomena
2008 - Pleiades Publishing | The Physics of Metals and Metallography
Leonid Afremov, Yury Kirienko,
The properties of ultrathin films have been studied within the framework of Ising model and the method of random-field interactions. It is shown that the Curie temperature is inversely proportional to the number of layers. Critical exponent has been obtained and it is shown that it does not depend on the type of crystalline lattice.
Tópico(s): Quantum many-body systems
2011 - Trans Tech Publications | Advanced materials research
Leonid Afremov, Petrov Aleksandr,
Using the method of the "average spin" a modelling study of magnetic and concentration phase transition in ultrathin antiferromagnetic of different crystalline structure has been carried out. It has been shown, that relative change of Neel temperature is subject to the power law with negative index which doesn't depend on the film's crystal kind. The calculation of the dependence of phase transition critical concentration in diluted magnetic material on the film thickness has been made out. The legitimacy ...
Tópico(s): Magnetic properties of thin films
2014 - IOP Publishing | Journal of Physics Conference Series
Leonid Afremov, Yury Kirienko, Alexander Petrov, Aleksandr Chepak,
Tópico(s): Characterization and Applications of Magnetic Nanoparticles
2023 - Springer Science+Business Media | Journal of Superconductivity and Novel Magnetism
Afremov Leonid, Petrov Aleksandr,
Influence of the size effect on the magnetic phase transition's temperature and magnetic moment of the nanowires was modelled based on average spin method. As it was shown that Curie temperature was increased with nanowires' sizes increase. The calculated value of the critical exponent of the spin-spin correlations v = 0.737 is close to experimental value.
Tópico(s): Surface and Thin Film Phenomena
2016 - IOP Publishing | Journal of Physics Conference Series
Leonid Afremov, Yury Kirienko,
In this paper we investigate the dependence of the magnetic states of heterophase particles on mechanical multiaxial stresses. It is shown that for such particles, there are four possible states, and the conditions of stability of these states are determined.
Tópico(s): Advanced Theoretical and Applied Studies in Material Sciences and Geometry
2012 - Trans Tech Publications | Advanced materials research
Leonid Afremov, I. G. Il’yushin, S. V. Anisimov,
Tópico(s): Magnetic Properties of Alloys
2015 - Pleiades Publishing | Izvestiya Physics of the Solid Earth
Leonid Afremov, V. I. Belokon, Konstantin Nefedev,
Tópico(s): Characterization and Applications of Magnetic Nanoparticles
2009 - Pleiades Publishing | Izvestiya Physics of the Solid Earth
Yury Kirienko, Leonid Afremov,
Temporary removed due to copyright issues.
Tópico(s): Statistical Mechanics and Entropy
2012 - Trans Tech Publications | Advanced materials research
Yury Kirienko, Leonid Afremov,
We propose a method for modeling the magnetic properties of nanomaterials with different structures. The method is based on the Ising model and the approximation of the random field interaction. It is shown that in this approximation, the magnetization of the nanocrystal depends only on the number of nearest neighbors of the lattice atoms and the values of exchange integrals between them. This gives a good algorithmic problem of calculating the magnetization of any nano-object, whether it is ultrathin ...
Tópico(s): Material Properties and Failure Mechanisms
2013 - IOP Publishing | Journal of Physics Conference Series
S. V. Anisimov, Leonid Afremov,
Tópico(s): Magnetic Properties and Synthesis of Ferrites
2018 - Pleiades Publishing | Izvestiya Physics of the Solid Earth
S. V. Anisimov, Leonid Afremov, Alexander Petrov,
Abstract Within the framework of the Ising model, in the direct exchange interaction approximation by the “average spin” method, the constant of the interphase exchange interaction A(T) , which determines the exchange bias field, is estimated. It was shown that A(T) ~ e (− T / T 0 ) , where the characteristic temperature T 0 is determined by the constant of the exchange interaction between the atoms of the core and the shell.
Tópico(s): Magnetic properties of thin films
2019 - IOP Publishing | Journal of Physics Conference Series
Leonid Afremov, Yury Kirienko, Alexander Petrov,
Tópico(s): Opinion Dynamics and Social Influence
2014 - Pleiades Publishing | Bulletin of the Russian Academy of Sciences Physics
Tatyana N. Gnitetskaya, Leonid Afremov, Elena B. Ivanova, Elena V. Karnauhova,
The article’s object is to analyze the content of one of the main nanoelectronics engeneer’s competence as an ability to conceive the scientific picture of the world, and provide conditions for students, future nanoelectronics engineers, to develop it. We discuss a content of the scientific picture of the world, its structure. We introduce a definition of the information picture of the world; suggest a method of structuring the physics course on the basis of distinguishing the object of research ...
Tópico(s): Innovations in Education and Learning Technologies
2013 - Trans Tech Publications | Advanced materials research
Leonid Afremov, Yury Kirienko,
Abstract. In this paper, we modelled the phase transition between ferromagnetic and paramagneticstates in ultrathin films of different crystal structure near the percolation transition. Properties of ultrathinfilms have been studied within the framework of Ising model and the method of random-fieldinteraction. It is shown that the critical concentration of such phase transition depends on the symmetryof crystal lattice of the material. The increase in the film thickness leads to a decrease of the ...
Tópico(s): nanoparticles nucleation surface interactions
2013 - Trans Tech Publications | Applied Mechanics and Materials
Within the frame of average spin model the calculation of dependence of critical phase transition temperature in antiferromagnetic ultrathin films of different crystalline structure on their thickness has been carried out. I has been shown, that relative change of Neel temperature is subject to power law with exponent close to the experimental values.
Tópico(s): Physics of Superconductivity and Magnetism
2013 - Trans Tech Publications | Advanced materials research
Petr Andriushchenko, Afremov Leonid, Chernova Mariya,
Small magnetic particles placed in a relatively soft polymer (with elastic modulus E ~ 10 ÷ 100 kPa) are magnetically soft elastomers.The external magnetic field acts on each particle which leads to microscopic deformation of the material and consequently to changing of its shape -magnetostriction.For purposes of studying of magnetostriction the model of movable cellular automata (MCA), in which a real heterogeneous material is an ensemble of interacting elements of finite sizeautomata, is used.It's supposed ...
Tópico(s): Elasticity and Material Modeling
2014 - IOP Publishing | Journal of Physics Conference Series
Afremov Leonid, Petrov Aleksandr,
The phase transition's critical temperature dependence of the thickness and critical magnetic concentration are studied using the method of configuration averaging over the interaction fields in the framework of the Ising model in amorphous ultrathin film to define the transition from ferromagnetic state to paramagnetic one. It is shown that the Curie temperature increases quickly with a rise in number of monolayers and critical magnetic concentration decreases to bulk material value.
Tópico(s): Magnetic properties of thin films
2015 - IOP Publishing | Journal of Physics Conference Series
Leonid Afremov, Yury Kirienko,
Tópico(s): nanoparticles nucleation surface interactions
2011 - Pleiades Publishing | The Physics of Metals and Metallography
Leonid Afremov, Yury Kirienko,
The theoretical analysis of the effect of uniaxial stress on the magnetization of the system of noninteracting nanoparticles is done by an example of heterophase particles of maghemite, epitaxially coated with cobalt ferrite. It is shown that stretching leads to a decrease in the coercive force H c , and compression leads to its growth. The residual saturation magnetization I rs of nanoparticles does not change. With increasing of interfacial exchange interaction, coercive force varies nonmonotonically.
Tópico(s): Characterization and Applications of Magnetic Nanoparticles
2012 - Trans Tech Publications | Advanced materials research
Leonid Afremov, V. I. Belokon,
Magnetic states of systems of interacting heterogeneous particles modeling a ferromagnetic rock are theoretically studied.Main attention is given to such important characteristics of the systems as the spontaneous magnetization, the critical field of an irreversible change in the grain magnetic moment, and the distribution of interaction fields.It is shown that particles with strongly imperfect lattices are characterized by a minimum concentration of "magnetic" ions n = n 0 (a percolation limit) enabling ...
Tópico(s): High-pressure geophysics and materials
2005 - | Rossijskij žurnal nauk o zemle/Russian journal of earth sciences
Leonid Afremov, Aleksandr A. Petrov,
Within the frame of average spin the dependence of Neel temperature of ultrathin antiferromagnetic film for FCC crystalline lattice on its thickness and the concentration of magnetic atoms has been defined. The λ values calculated by us are close to experimental values obtained for the films СoO/SiO2. The increasing of thickness leads to decreasing of the critical concentration down to the value equal to percolation threshold.
Tópico(s): Characterization and Applications of Magnetic Nanoparticles
2014 - Scientific.net | Diffusion and defect data, solid state data. Part B, Solid state phenomena/Solid state phenomena
В. Н. Харитонов, Leonid Afremov, Ilia G. Iliushin, Pavel S. Mushtuk,
Atomistic simulations are carried out in the framework of layer-by-layer and combined oxidation models of the effect of cobalt oxidation on the hysteresis characteristics of Pd/Co films at temperatures $T>T_{N}$ . It is shown that an increase in the relative volume of the cobalt oxide (CoO) $V$ leads to a linear decrease in the magnetic moment saturation of the Pd/Co/CoO film, regardless of the model chosen. The effect of oxidation on the coercivity $H_{c}$ of the film is expressed in two features: ...
Tópico(s): Physics of Superconductivity and Magnetism
2023 - IEEE Magnetics Society | IEEE Transactions on Magnetics
Leonid Afremov, L. O. Brykin, I. G. Il’yushin,
Tópico(s): Theoretical and Computational Physics
2023 - Pleiades Publishing | The Physics of Metals and Metallography
Tópico(s): Geophysics and Sensor Technology
2009 - Pleiades Publishing | Izvestiya Physics of the Solid Earth