Search

Microwave circulators based on magnetic nanocomposites made of opal matrices are mathematically simulated and experimentally studied. Mathematical models are based on the solution of the 3D diffraction problems using the projection method and the decomposition computational algorithm that employs autonomous units with magnetic nanoinclusions and virtual Floquet channels. The computational algorithm developed using the projection method with effective parameters of the magnetic nanocomposite is used to calculate the S parameters of the scattering matrix of the microwave Y circulator based on the opal-matrix magnetic nanocomposite. The S parameters (real loss, isolation between arms, and reflection coefficient) of the Y circulator are measured for several nanocomposites made of opal matrices with magnetic nanoparticles (Co0.5Zn0.5Fe2O4 and Ni0.5Zn0.5Fe2O4) and compared with the parameters of the circulator based on magnesium–manganese ferrite in a frequency interval of 14–18 GHz. The simulated results are compared with the experimental dependences.

Periodic 3G lattices made of oriented magnetic nanowires are considered under the magnetic resonance in the millimeter-wavelength range. The propagation of electromagnetic waves in anisotropic nanostructured materials based on these lattices is mathematically modeled using the method of autonomous blocks with virtual Floquet channels. The real and imaginary parts of propagation coefficients of longitudinal (clockwiseand counterclockwise polarized) and transverse (ordinary and extraordinary) waves for the zero spatial harmonic of 26 GHz are electrodynamically calculated. These waves propagate in 3D lattices of magnetic (Co80Ni20, Fe) nanowires. The obtained results depend on the intensity of the external constant magnetic field and the lattice period. The methods of control of the frequency dispersion in the millimeter-wavelength range under the influence of the external magnetic field and under the change of the geometry of lattices are determined. It is considered that the direction and intensity of the magnetic bias, its orientation with respect to the nanowire axis, and the mutual orientation of the constant and high-frequency magnetic fields vary.

A mathematical model of the electromagnetic wave diffraction by specimens of anisotropic nanocomposite materials (3D lattices of oriented carbon nanotubes (CNTs) with magnetic nanoparticles and magnetic nanowires) in waveguides is developed. It is made with the help of a computational algorithm based on a multilevel recomposition and the method of autonomous blocks with the Floquet channels. The transmission coefficients of the H10 wave with the frequency of 26 GHz that propagates through plates of magnetic nanocomposites in a waveguide are electrodynamically calculated as dependences of an external constant magnetic field (a magnetic bias field) and the number of magnetic nanoparticles filling the CNT.

Mathematical modeling of propagation of electromagnetic waves in 3D periodic lattices of oriented carbon nanotubes (CNs) with magnetic nanoparticles in the millimeter wave band is performed. Real and imaginary parts of complex propagation coefficients of longitudinal (counterclockwise polarized and clockwise polarized) waves and transverse (ordinary and extraordinary) waves (the zero spatial harmonic) propagating in a 3D lattice of oriented CNs with magnetic nanoparticles are calculated at frequency f = 26 GHz as functions of the intensity and direction of the external magnetostatic field for different numbers of magnetic nanoparticles taken into account in an elementary cell (an autonomous block with virtual Floquet channels) of the model.

A probabilistic model of the resonance interaction of electromagnetic waves with magnetic 3D nanocomposities is developed. It is assumed that the field of the ferromagnetic resonance (FMR) of nanoparticles located in cavities of the dielectric matrix is a random variable distributed according to the normal law. The mathematical expectation of the random values of the real and imaginary parts of the diagonal and off-diagonal components of the tensor effective permeability of a 3D magnetic nanocomposite based on the opal matrix containing Ni0.7Zn0.3Fe2O4 nanoparticles is calculated. The experimental and calculation data of the probabilistic model are compared.

An electrodynamically rigorous mathematical model is developed for calculating the components of the tensor effective permeability of 3D nanocomposites with allowance for exchange and boundary conditions. A computational algorithm based on the method of autonomous blocks with Floquet channels is developed. With the help of this algorithm, the real and imaginary parts of the diagonal and off-diagonal components of the tensor effective permeability of a 3D opal-matrix nanocomposite are calculated. The simulation results are compared to experimental dependences.

The TEM wave diffraction by a periodic lattice of magnetic nanowires has been simulated mathematically in the terahertz frequency range. The computational algorithm based on autonomous blocks with virtual Floquet channels loaded by magnetic nanoinclusions has been developed and used to perform the electrodynamic analysis of the scattering matrix parameters constructed for a 2D periodic lattice of longitudinally magnetized ferromagnetic (iron) nanowires at a frequency of 30 THz. It is demonstrated that the maximum of the transmission coefficient of a TEM wave propagating through a ferromagnetic nanowire lattice can be controlled by the constant magnetizing field near the antiresonance point and depends on the geometry and dimensions of nanowires and the lattice.

A decomposition method is developed for simulation of microwave- and infrared-band devices containing magnetic nanomaterials and magnetophotonic crystals. The method is based on autonomous blocks that are rectangular parallelepipeds with magnetic nanoinclusions and virtual Floquet channels (referred below as magnetic Floquet autonomous blocks (MFABs)) on the faces. A computational algorithm of solution of a nonlinear diffraction boundary value problem by means of the Galerkin method is developed for constructing MFAB descriptors. The coefficient of TEM wave transmission through a lattice of ferrite nanospheres is calculated. The threshold values of the pumping-wave amplitude such that exchange spin waves are parametrically excited in ferrite-nanosphere lattices are determined from bifurcation points of the nonlinear Maxwell operator. This excitation is observed when distances between magnetic nanoparticles are reduced to the exchange-interaction length.

A mathematical model is developed for propagation of electromagnetic waves in periodic magnetic nanostructures. The model is based on the decomposition approach and autonomous blocks (ABs) with magnetic nanoinclusions and Floquet channels. The Floquet theorem is used to derive the characteristic equation for constants of wave propagation in 3D periodic nanolattices. The equation involves the scattering matrix (descriptor) of ABs. The propagation constants of longitudinal (right- and left-handed polarized) waves and transverse (ordinary and extraordinary) waves in a lattice of ferromagnetic metal nanospheres are calculated in the microwave band as functions of the lattice period. A technique is developed for electrodynamic calculation of the effective electromagnetic parameters of nanostructured gyromagnetic media, and the complex values of the components of the effective tensor permeability and permittivity are found as functions of the ratio of the nanoparticle radius and the lattice period.

A strip-slot guiding structure (GS) containing a distributed semiconductor inclusion with a negative differential conductivity is considered. Instabilities and nonlinear effects observed during propagation of electromagnetic waves in such a structure are investigated via numerical analysis of branching points of solutions to the nonlinear Maxwell equations. The method of universal autonomous blocks with Floquet channels is applied to solve the 3D problem of diffraction of electromagnetic waves by a nonlinear semiconductor irregularity in a strip-slot GS. The solutions obtained describe frequency multiplication and generation of the GS fundamental mode near a branching point. The generation process is described as a function of the incident-wave amplitude. The bifurcation points of the nonlinear Maxwell operator are found numerically with allowance for bounding geometries. These points specify the self-oscillation frequencies in planar Gunn effect diodes in a strip-slot GS.

A method is developed for simulation of nonlinear propagation and diffraction of electromagnetic waves in guiding structures containing highly nonlinear distributed semiconductor inclusions. A planar Gunn effect diode located in a strip-slot guiding structure is considered, and the nonlinear effect of frequency multiplication in such a diode is simulated. The simulation is performed with the use of a computational algorithm based on universal autonomous blocks with Floquet channels.

A method is proposed for bifurcation analysis of electrodynamic structures containing nonlinear media. The method uses bifurcation points of the nonlinear Maxwell operator for a 3D electrodynamic problem. A computational algorithm is developed for analyzing bifurcation points of the nonlinear Maxwell operator. The algorithm involves linearization of nonlinear electrodynamic systems with distributed gyromagnetic inclusions. The method of universal autonomous blocks with virtual Floquet channels and a characteristic determinant are applied to investigate a linearized system. Nonlinear and parametric oscillations in a resonator structure with a ferrite inclusion are analyzed numerically by means of the computational algorithm for analysis of bifurcation points of the nonlinear Maxwell operator.

The structure of normal waves in a rectangular Floquet channel is investigated. A boundary value electrodynamic problem for an autonomous block (AB) in the form of a rectangular homogeneous parallelepiped with virtual Floquet channels is formulated and solved. Analytic expressions for descriptors of an AB are obtained. Methods of recomposition of ABs are developed. Strip-slotted structures are simulated. The simulation results are compared to the results obtained with the use of alternative methods, and the efficiency of the method proposed is assessed.

A numerical method is developed for solution of 3D nonlinear boundary value problems of electromagnetics. The method proposed is applied for the numerical investigation of propagation, diffraction, and distributed interaction of electromagnetic waves in a strip-slot waveguiding structure containing a ferrite inclusion.