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Yury Kirienko

Publications and source records attributed to Yury Kirienko.

7 recordsLinked to original sources
arXiv2024

Theory of Turbulence for $d \rightarrow \infty$: Four-Loop Approximation of the Renormalization Group

Within the framework of the renormalization group approach in the stochastic model of fully developed turbulence, the $β$-function has been calculated in the fourth order of perturbation theory for high-dimensional spaces $d \rightarrow \infty$. The position of the fixed point of the renormalization group in the fourth order of the $\varepsilon$-expansion has been determined, and the index $ω$, which defines the infrared stability of this point, has been calculated. We demonstrate the possibility of significantly reducing the number of Feynman diagrams through mutual cancellation. The results obtained allow us to find the four terms of the $\varepsilon$-expansion of the index $ω$: $$ ω= 2\,\varepsilon + \frac{2}{3}\,\varepsilon^2 + \frac{10}{9}\,\varepsilon^3 + \frac{56}{27}\,\varepsilon^4. $$

cond-mat.stat-mech↗
arXiv2014

Phase Transitions in Systems with Finite Number of Atoms

Properties of nanoparticles have been studied within the framework of Ising model and the method of random-field interactions: the average magnetic moment and position of critical points of the magnetic and the concentration phase transitions depending on their size. It is shown that the Curie temperature is inversely proportional to the size of the particle. Critical concentration of the ordered state decreases with increasing of size of nanoparticles until the percolation threshold of "massive" particles.

cond-mat.mes-hall↗
arXiv2013

Modeling of the magnetic properties of nanomaterials with different crystalline structure

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 film or nanoparticle of any shape and structure, managing only a rule of selection of nearest neighbors. By setting different values of exchange integrals, it is easy to describe ferromagnets, antiferromagnets, and ferrimagnets in a unified formalism. Having obtained the magnetization curve of the sample it is possible to find the Curie temperature as a function of, for example, the thickness of ultrathin film. Afterwards one can obtain the numerical values for critical exponents of the phase transition "ferromagnet -- paramagnet". Good agreement between the results of calculations and the experimental data proves the correctness of the method.

physics.gen-ph↗
arXiv2012

Effect of mechanical stresses on coercive force and saturation remanence of ensemble of dual-phase interacting nanoparticles

In the dual-phase model of interacting nanoparticles stretching leads to a decrease in both coercive force $H_c$ and saturation remanence $I_{rs}$, and compression - to their growth. Magnetostatic interaction between particles also decreases both $H_c$ and $I_{rs}$. Theoretical analysis was carried out in the framework of the dual-phase system of interacting particles on the example of nanoparticles $γ$-$Fe_2O_3$, epitaxially coated with cobalt.

cond-mat.mes-hall↗
arXiv2012

Effect of mechanical stresses on the coercive force of the heterophase non-interacting nanoparticles

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

cond-mat.mes-hall↗
arXiv2011

Magnetic phase transitions in ultrathin films of different crystal structures

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 $ν$ has been obtained and it is shown that it does not depend on the type of crystalline lattice.

cond-mat.mes-hall↗