Gradient Structures of Ni-Zn Ferrites for Electromagnetic Radiation Protection Devices

摘要

Increasing the reliability requirements for electromagnetic compatibility of electronic equipment requires the creation of protective coatings that absorb electromagnetic radiation or the development of new radio-absorbing materials. In the frequency range up to 1 GHz, radio-absorbing materials based on Ni–Zn ferrites are of the greatest interest. The absorption of electromagnetic radiation by ferrites occurs owing to resonant phenomena at the level of domains and atoms. Improving the performance of ferrites is possible by modifying their surface properties. In this paper, gradient structures for products of electromagnetic radiation protection are obtained by treating the surface of Ni–Zn ferrite samples with a low-energy electron beam. To generate the electron beam, a unique installation was used—a fore-vacuum plasma electronic source that allows forming and transporting a beam with a power density of up to 10~(5)W/cm~(2)under conditions of high pressure and high gas outflow. As a result of processing, gradient structures were found on the surface of ferrites. A theoretical analysis and experimental study was carried out for the obtained “nonmagnetic conductor–ferrite” structures characterized by an increased attenuation coefficient and a reduced reflection coefficient of electromagnetic radiation in the frequency range from 0.5 to 2.5 GHz. The possibility of obtaining near-surface layers depleted in zinc with increased electrical conductivity and reduced magnetic permeability is shown.