Vol 70, No 4 (2025)

The results of papers are presented in which dispersion properties of electroacoustic waves in the gap structure of two different piezoelectrics are considered. In particular, it is shown that in the presence of a difference of shear wave velocities in piezoelectrics there are no purely symmetric and antisymmetric modes, and the coefficients of the boundary localization of the shear wave will be significantly different. It is established that at a certain equal level of loss and gain (PT is a symmetrical structure) of two identical piezoelectrics of symmetry class 6, the symmetric and antisymmetric modes intersect. The intersection point defines an exceptional point of the PT-symmetric structure. Taking into account the unequal level of loss and gain in piezoelectrics results in either intersection, touching, or convergence of two modes at the point of their degeneracy (exceptional point) in the shear wave spectrum. As in the case of a purely PT-symmetric structure, the frequency dependence of the amplitude at an exceptional point of a quasi PT-symmetric structure (with a rather small difference in loss and gain levels) exhibits a very narrow peak, which opens up the possibility of creating hypersensitive sensors based on them.

The concept of an idealized passive element of complex fractional order γ = α + jβ, a synonym for which is an ideal complex fractal element (ICFE), is introduced. The corresponding basic and derived parameters of the ICFE are introduced. It is shown that the ICFE is a generalized two-pole passive element of fractal radio electronics, which generalizes the properties of not only all existing idealized passive two-pole elements, but also infinitely expands the capabilities of the modern element base. A classification of all existing two-pole passive idealized passive elements is given depending on the value of the complex fractional impedance index. The dimensions and physical meaning of these elements are determined depending on the values of α and β.

The operation of a spintronic detector in the near field of an antenna emitting a microwave signal at a frequency of 10 GHz has been investigated. The feasibility of using a detector based on a Lu₃Fe₅O₁₂/Pt heterostructure, operating due to the inverse spin Hall effect, has been studied. A comparison was made between the experimentally measured output voltage of the detector and theoretical calculations of the power distribution of the electromagnetic field, performed using COMSOL Multiphysics. The sensitivity of the detector was determined, and the dependence of the output signal on the distance to the radiation source was measured. The obtained results confirm the feasibility of using spintronic heterostructures in wireless data and energy transmission systems. The prospects for using the detector in wireless communication and data transmission systems operating in the near field of an antenna, such as RFID (Radio Frequency Identification) and NFC (Near Field Communication), are considered.

The results of the development and creation of various specialized optical fibers (SOF) for use in science and technology are presented. Methods of creating SOFs with Bragg structures recorded in the light-guiding core are described directly during the process of extracting SOF. Reflective signal sensors and single-frequency laser complexes were created on the basis of these sensors. Fiber-based refractive index meters for liquids were obtained using precise thinning of reflective claddings and nanocoatings. Ways of using multi-core SOFs and possibilities for creating end devices based on them have been shown.

The paper presents the results of a study of the features of spin wave propagation in a magnon crystal based on a nanoscale ferromagnetic film with a periodic system of grooves on the surface. Micromagnetic modeling was performed in the MuMax3 environment. It is established that additional hybrid modes on the dispersion characteristic for a magnon crystal near each main width mode are formed. The ratio of ridge to groove widths affects the energy distribution between hybrid modes and the cutoff frequency of the main modes. The influence of the ridge/groove ratio on the formation of band gaps based on dispersion and amplitude-frequency characteristics is analyzed. It is shown that the most pronounced band gaps are observed for large ridge/groove width ratios. Also, an increase in the ridge/groove ratio and an increase in the groove depth leads to an increase in the number of orders of pronounced Bragg resonances.

The properties of exchange spin waves (ESW) in epitaxial films of yttrium iron garnet (YIG) are investigated in this paper. A comprehensive analysis of the peculiarities of excitation, propagation, and interaction of ESW is carried out, taking into account their anisotropic properties. A methodology for calculating the dispersion and energy characteristics of waveguide modes of ESW for various directions of wave propagation in tangentially magnetized YIG films is proposed. It is established that the presence of both elliptical and linear polarization of precession waves leads to the deformation of the trajectory of the magnetization precession vector and a change in the orientation of the symmetry axes of the elliptical trajectory. Good agreement between the calculated and measured characteristics of ESW has been experimentally confirmed. The obtained results allow for the creation of new types of functional devices for information transmission, storage, and processing based on short-wavelength exchange spin waves.