Doklady Rossijskoj akademii nauk. Fizika, tehničeskie nauki
ISSN (print): 2686-7400
Media registration certificate: № FS 77 - 77142 dated 06.11.2019
Founder: Russian Academy of Sciences
Editor-in-Chief Garnov Sergey Vladimirovich
Number of issues per year: 6
Indexation: RISC, White List (level 3)
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Volume 521, Nº 1 (2025)
ФИЗИКА
On the Scientific Results Obtained in 2022–2023 at the Institutes of the Physical Sciences Division of the Russian Academy of Sciences
Resumo
The results described here are based on the materials of annual reports presented by the Head of the Physical Sciences Division of the Russian Academy of Sciences at the General Meetings of the Division in 2023 and 2024 and provide a picture of the scientific achievements obtained in the field of physical sciences in the period 2022–2023 at the research institutions under the individual powers of the Russian Academy of Sciences stipulated by the regulations of the Government of the Russian Federation no. 521 dated June 5, 2014, and no. 1652 dated December 24, 2018.
3-30
Nature of the Ferromagnetic Griffiths Phase
Resumo
A simple model of a disordered cluster ferromagnetic phase is proposed, in which magnetic disorder is determined by random local magnetic fields Hl with a power-law distribution function w ~ |Hl |–ξ (ξ < 1), which allows analytically describing the experimentally known magnetic properties of Griffiths ferromagnetic phases from a unified point of view, including the transition from the Curie–Weiss law for magnetic susceptibility χ ~ 1/(T–TC) to an anomalous power-law dependence χ ~ 1/(T–TC)ξ in the range of temperature T exceeding the Curie temperature TC. The developed approach makes it possible for the first time to explain the appearance of a power-law dependence of magnetization M on the magnetic field H, M ~ H1– ξ, in the ferromagnetic region T < TC and to propose a method for experimental determination of the order parameter. Comparison with experimental data leads to conclusion that it is precisely the disorder of this type that plays the main role in ferromagnetic Griffiths systems, and the division into magnetic clusters should be valid for temperatures both above and below the Curie point. It is shown that the peculiarities of the magnetic properties of the Griffiths cluster system are not associated with the anomalous behavior of the magnetization of an individual cluster, but arise as a result of the disorder-induced modification of the integral characteristics of a disordered ferromagnet.
31-38
Effect of Magnetic Field on Thermal Conductivity of Nitrogen-Doped Diamond
Resumo
The measurement of the thermal conductivity κ(T) of a single crystal of nitrogen-doped diamond in the temperature range from 6 to 92 K in a magnetic field of 14 T is reported. A weak effect of the magnetic field on κ(T) at low temperatures is found. The process of phonon scattering on bound charge carriers of an impurity under conditions of strong Zeeman splitting is discussed.
39-43
МЕХАНИКА
The Method of Computer Simulation of Seismic Vibrations Buried Structures, Taking into Account the Interaction with the Soil Base
Resumo
An effective method for numerical simulation of seismic vibrations of buried structures is presented, taking into account the nonlinear interaction with the ground base. The novelty of the proposed approaches lies in the application of the superimposed grid method to separate incident, transmitted and reflected waves in the ground base at the boundary of the calculated subdomain in contact with the structure, as well as the use of quasi-uniform grids with linear viscosity to dampen radiated waves, reduce the dimension of a discrete finite element problem and reduce computational costs. An assessment of the applicability of a two-dimensional planar formulation to solve the three-dimensional problem of earthquake resistance of structures is made.
44-49
Chaotic, Hyperchaotic Vibrations and Stability of Porous Euler–Bernoulli Beams Considering Physical and Geometrical Nonlinearities
Resumo
A mathematical model of flexible (according to the theories of T. von Karman and Green–Lagrange) physically nonlinear porous size-dependent Euler-Bernoulli beams subjected to transversal alternating loading is developed. The required differential equations are derived from the Hamilton–Ostrogradsky principle. Iterative algorithm is developed to compute chaotic and hyperchaotic vibrations in a mechanical system with “almost” infinite degrees of freedom. These algorithm include the Finite Difference Method (FDM) combined with Birger's Method of Variable Elasticity Parameters (MVEP), which takes into account physical nonlinearity. Chaos is analysed according to Gulick's definition. The instability of beam structures, including both metallic continuous and porous functionally graded Euler–Bernoulli beams, is studied within the framework of the Lavrentiev–Ishlinsky and Rayleigh–Taylor concepts.
50-58