Magnetic absorbing material refers to the material that can absorb or substantially reduce the electromagnetic wave energy projected on its surface, thereby reducing the interference of electromagnetic wave. In engineering applications, the absorbent material is required to have a high absorption rate of electromagnetic wave in a relatively wide band, and it is also required to have light weight, temperature resistance, moisture resistance, corrosion resistance and other properties.
1) resistance type loss. Such absorption mechanism is related to the resistivity loss of the material conductivity, that is, the higher the conductivity, the greater the macroscopic current caused by the carrier (including the current caused by the change of electric field and the eddy current caused by the change of magnetic field), thus facilitating the conversion of electromagnetic energy into heat energy.
2) dielectric loss. It is a kind of dielectric loss absorption mechanism related to the electrode, that is, electromagnetic energy is converted into heat energy dissipation through the "friction" generated by the repeated polarization of the medium. The process of dielectric polarization includes electron cloud displacement polarization, polar medium electric moment polarization, ferroelectric domain polarization and wall displacement.
3) magnetic loss. Such absorption mechanism is a kind of magnetic loss related to the dynamic magnetization process of ferromagnetic medium, which can be refined into hysteresis loss, rotating magnetic eddy current, damping loss and magnetic aftereffect, etc. The main sources are domain shifting, domain wall displacement and natural resonance of magnetic domain similar to hysteresis mechanism. In addition, the latest microwave loss mechanism of nanomaterials is a hot topic in the analysis of absorbing materials.