Section 1. Topics on theoretical electrodynamics

ELECTRON-ELECTRON INTERACTION IN TWISTED BILAYER GRAPHENE AT LARGE TWIST ANGLES: RENORMALIZATION OF FERMI LIQUID PARAMETERS

Sboychakov A. O., Rozhkov A. V.

Abstract 

 We study the impact of the electron-electron interaction on the properties of the Fermi-liquid of twisted bilayer graphene. We consider the structures having small enough sizes of the supercell, which corresponds to the large twist angles. In this case, single-particle spectrum has a gap at the Fermi level due to the hybridization of electrons moving in different layers. Electron-electron interaction renormalizes the parameters of the single-particle Hamiltonian. We calculate the quasiparticle residue as well as the renormalized Fermi velocity and the gap as functions of the bare gap. We show, in particular, that that the renormalized gap can be approximately two times larger than the bare one.

Keywords: graphene, electronic structure, electron-electron interaction

ABOUT MAGNETIC ENERGY OF FERROMAGNETIC PARTICLE WITH CAVITY

Sboychakov A. O.

Abstract 

We study composite materials consisting of ferromagnetic particles embedded into a non-magnetic dielectric medium. It is assumed that ferromagnetic particles are not fulfilled, but contain a cavity, the dimension of which can be of the order of the size of the particle itself. In this work we model the particles by balls with a cut-out core. The aim of this work is to find out the possible distribution of the magnetization inside such a particle, which is optimal in terms of its magnetic energy. For this purpose, three possible magnetic configurations are considered: a uniformly magnetized state, a state with two magnetic domains, as well as a state in which the magnetization is inhomogeneous and twisted in a certain plane. It is shown that under certain assumptions about the properties of the magnetic anisotropy, the third configuration is the optimal of the three considered if the particle size (its radius and thickness of the ferromagnetic region) is much larger than the exchange length.

Keywords: magnetic composites, magnetostatics, magnetic anisotropy, domain structure

Section 2. Topics on computer simulation in electrodynamics

FORMATION OF THE RADIATION PATTERN OF A BROADBAND ANTENNA FOR USING IT AS IRRADIATOR

Gilmutdinov R. V., Menshikh N.L., Solosin V. S., Fedorov S.A.

Abstract 

 In this work, the opportunity of applying broadband antennas as feeds for reflector collimators was investigated. Two types of feeds (original and modified) based on the Satimo SH2000 broadband antenna were considered. An approximate computer model of a compact range with a MARK-12 reflector has been created. The field in the quiet zone was calculated using the physical optics method. A comparison was made of the field characteristics obtained using different feeds. The contribution of a smoothly varying field component to the unevenness of the field distribution has been studied. The dependence of amplitude and phase unevenness on frequency was described. It was shown that the use of an feed with a modified radiation pattern makes it possible to reduce the unevenness of the field amplitude in the quiet zone throughout the entire frequency band and maintain acceptable phase unevenness.

Keywords: compact range, FEKO, feeds, collimator, quiet zone

Section 3. Topics on interaction of an electromagnetic field with materials

METAMATERIAL WITH MECHANICAL STRENGTH AND DIELECTRIC PERMITTIVITY IS CLOSE TO UNITY. IMPROVED CONSTRUCTION

Baskov К.М., Krasnolobov I.I., Semenenko V.N., Furmanova T.A., Chistyaev V.А.

Abstract 

The article is a continuation of the work in which the electrodynamic properties of a mechanically strong metamaterial with a dielectric constant close to unity were investigated. In previous work, it was shown that such a material can be effective in creating radomes shelters. At the same time, such a metamaterial has a significant drawback, namely, it has a spatial dispersion of magnetic permeability when a E polarized electromagnetic wave falls on a layer of such material. This article is devoted to research aimed at eliminating this shortcoming and, as a result, improving the radio engineering quality of such a metamaterial. The article shows that the inclusion in the composition of the metamaterial of an additional periodic lattice of thin spirals installed perpendicular to its surface makes it possible to significantly reduce the dependence on the angle of incidence of magnetic permeability, which is observed when a E polarized wave falls on the metamaterial.

Keywords: metamaterial, antenna, radome, transmission coefficient, permittivity

LAMINATED NANOMATERIALS FOR MICROWAVES: FEATURES AND LIMITATIONS

Osipov A.V., Bobrovsky S.Yu., Zezulina P.A., Lagarkov A.N., Maklakov S.A., Maklakov S.S., Petrov D.A., Rozanov K.N., Ryzhikov I.A., Shiryaev A.O.

Abstract 

 Many problems of microwave technology needs bulk materials with the highest possible values of permeability at microwaves. It is known that these values are achievable with use of thin ferromagnetic films. The article presents an overview of the results obtained during the development of a new type of composite materials - laminates of multilayer thin ferromagnetic films deposited onto a polymer substrate; theoretical assessments of their application and limitations found under study are considered, the current state of affairs and development prospects are assessed.

Keywords: microwave measurements, magnetic materials, thin films, microwave permeability, ferromagnetic resonance

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