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Makeeva G.S.,Penza State University | Golovanov O.A.,Penza State University | Rinkevich A.B.,RAS Institute of Metal Physics | Samoylovich M.I.,Central Research Technological Institute TECHNOMASH
European Microwave Week 2014: Connecting the Future, EuMW 2014 - Conference Proceedings; EuMC 2014: 44th European Microwave Conference

A numerical technique for the accurate modeling of nonreciprocal microwave devices (MDs) based on magnetic nanocomposites by using rigorous mathematical models to solve the 3D diffraction boundary problems is developed. The models are based on the solution of Maxwell's equations with electrodynamic boundary conditions complemented by the Landau-Lifshitz equation with the exchange term. Using the decomposition algorithm based on the projection method by autonomous blocks with magnetic nanoinclusions and virtual Floquet channels (MFABs) the elements of multimode multi-channel scattering matrix of magnetic opal nanocomposite-based circulators were calculated at microwave frequencies. The waveguide transmission and reflection measurements of scattering parameters of the circulators based on magnetic opals were performed at frequencies from 14 GHz to 38 GHz. The numerical technique shows an excellent agreement with experimental data. It is shown that the magnetic opal nanocomposite-based circulators have improved performances: bigger isolation, smaller insertion losses and a wider pass band as compared to ferrite-based MDs. © 2014 European Microwave Association. Source

Tsvetkov M.Y.,Russian Academy of Sciences | Khlebtsov B.N.,Russian Academy of Sciences | Khanadeev V.A.,Russian Academy of Sciences | Bagratashvili V.N.,Russian Academy of Sciences | And 3 more authors.
Nanoscale Research Letters

We describe a new approach to the fabrication of surface-enhanced Raman scattering (SERS) substrates using gold nanorod (GNR) nanopowders to prepare concentrated GNR sols, followed by their deposition on an opal-like photonic crystal (OPC) film formed on a silicon wafer. For comparative experiments, we also prepared GNR assemblies on plain silicon wafers. GNR-OPC substrates combine the increased specific surface, owing to the multilayer silicon nanosphere structure, and various spatial GNR configurations, including those with possible plasmonic hot spots. We demonstrate here the existence of the optimal OPC thickness and GNR deposition density for the maximal SERS effect. All other things being equal, the analytical integral SERS enhancement of the GNR-OPC substrates is higher than that of the thick, randomly oriented GNR assemblies on plain silicon wafers. Several ways to further optimize the strategy suggested are discussed. © 2013 Tsvetkov et al. Source

Samoylovich M.I.,Central Research Technological Institute TECHNOMASH | Talis A.L.,RAS Nesmeyanov Institute of Organoelement Compounds
Crystallography Reports

The developed apparatus of the "structural application" of algebraic geometry and topology makes it possible to determine topologically stable helicoidally-like packings of polyhedra (clusters). A packing found is limited by a minimal surface with zero instability index; this surface is set by the Weierstrass representation and corresponds to the bifurcation point. The symmetries of the packings under consideration are determined by four-dimensional polyhedra (polytopes) from a closed sequence, which begins with diamondlike polytope {240}. One example of these packings is a packing of tetrahedra, which arises as a result of the multiplication of a peculiar starting aggregation of tetrahedra by a fractional 40/11 axis with an angle of helical rotation of 99. The arrangement of atoms in particular positions of this starting aggregation allows one to obtain a model of the α-helix. This apparatus makes it possible to determine a priori the symmetry parameters of DNA double helices. © 2013 Pleiades Publishing, Ltd. Source

Ciou Y.S.,National Cheng Kung University | Lee M.K.,National Cheng Kung University | Lee M.K.,Instrument Center at | Charnaya E.V.,National Cheng Kung University | And 5 more authors.
Superconductor Science and Technology

An ac magnetization technique was used to study superconductivity in tin loaded nanoporous silica matrices, opal matrix and two porous glasses. The behavior of type-II superconductors with a sharp transition at zero bias field was observed. Regular increase in the superconducting temperature up to 4.2 K and in a critical field up to Hc2(0) ≅ 54 kOe with decreasing pore size was found. A crossover from the upturn to the common downturn curvature in the Hc2(T) line was seen for all nanocomposites; the upturn curvature was more pronounced for the matrix with the finest pores. © 2013 IOP Publishing Ltd. Source

Rinkevich A.B.,RAS Institute of Metal Physics | Perov D.V.,RAS Institute of Metal Physics | Demokritov S.O.,RAS Institute of Metal Physics | Demokritov S.O.,University of Munster | And 2 more authors.
Photonics and Nanostructures - Fundamentals and Applications

Metamaterials based on opal matrix and containing magnetic particles are studied both experimentally and theoretically and their complex refractive coefficients at frequencies of millimeter waveband are obtained by comparing the results of calculations with the experimental data on transmission and reflection coefficients and their variations with an applied magnetic field. The metamaterials under study contain metallic cobalt, nickel and iron particles, nickel-zinc ferrite and silver particles, or ferrite-garnet Nd3Fe5O12 particles. A parameter, characterizing the nonuniformity of electromagnetic fields at different distances from a magnetic particle, has been introduced and calculated. It is found that the nonuniformity drastically varies depending on the distance from magnetic particle and on external magnetic field. © 2015. Source

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