Natural resonance is the main mechanism by which ferrite absorbs electromagnetic waves. Natural resonance refers to the precession resonance of ferrite produced by the combined action of the incident alternating magnetic field and the magnetic anisotropy equivalent field of the crystal without an external constant magnetic field. When the angular frequency of the alternating magnetic field is equal to the intrinsic angular frequency determined by the equivalent field of magnetic anisotropy of the crystal, the ferrite absorbing material will absorb a large amount of electromagnetic wave energy.
According to different microstructures, ferrite can be divided into three main series: spinel type, magnetoplumbite type and garnet penalties. At present, there are more researches on the first two, and less research on garnet punishment.
Spinel ferrite has a long history of research and application, but because its electromagnetic parameters are difficult to meet the principle of relative permittivity and relative permeability as close as possible, it is difficult for a single material to meet the frequency bandwidth, thin thickness and surface area. For low density requirements, the powder is often dispersed into magnetic particles to make composite ferrite materials. The electromagnetic parameters of the ferrite can be adjusted through the particle size and composition of the ferrite to improve the wave absorbing performance of the ferrite.
The hexagonal magnetoplumbite type has a higher self-heating resonance frequency due to its higher magnetic anisotropy equivalent field, and is usually used as an absorber in the centimeter wave band and millimeter wave band, or is doped to further expand the frequency band. Ferrite absorbing materials have been widely used in stealth technology. Introduction to the above article