SIMULATION OF PROPAGATION OF ELECTROMAGNETIC WAVES IN RADIO-ABSORBING Ni–Zn FERRITES

10.25712/ASTU.1811-1416.2023.03.005

Abstract

Nickel-zinc (Ni–Zn) and magnesium-zinc ferrites (Mg–Zn), as well as composites based on them, are one of the most promising radio absorbing materials that can effectively absorb electromagnetic radiation in the frequency range from several MHz to units of GHz. Many questions related to the radio-absorbing properties of these materials still remain open, which is a consequence of the influence of the sample parameters, both on the frequency dependences of the magnetic and dielectric permittivity, and on the parameters of the domain walls. Within the framework of this work, a mathematical model of the process of propagation of electromagnetic waves in radio-absorbing Ni–Zn ferrites is proposed. Boundary and initial conditions are set that take into account the geometry and microstructure of the samples. The solution of the formulated boundary value problem on a segment using the method of separation of variables or the Fourier method showed that the amplitude of the electromagnetic wave decreases significantly after passing half the thickness of the sample, which corresponds to the high radio absorbing properties of the investigated Ni–Zn ferrites. A numerical analysis of the reflection of a plane polarized wave from a two-layer structure Ni–Zn ferrite/metal plate in the frequency range to 100 MHz was carried out. The simulation results are verified by experimental data on the radio absorbing properties of Ni–Zn ferrites of the 1000NN brand. It is shown that the use of the assumption of the exponential nature of the dependences of the dielectric and magnetic permeability on the normalized coordinate is applicable only in a narrow frequency range up to 3 MHz, for which the experimental data and the results of numerical analysis are in good agreement.