Microstructural and Microwave Electromagnetic Properties of FeCoB-SiO2 Film on PET Substrate

Microstructural and electromagnetic properties of FeCoB-SiO2 films prepared on PET substrates by radio- frequency sputtering were investigated. The as-deposited FeCoB-SiO2 films are found to be amorphous with an electrical resistivity of 1755.73 μΩ·cm and a saturation magnetization of 0.7 T. Because of the existence of nonmagnetic matrix resistance to magnetic wall displacement, those FeCoB-SiO2 films have a substantially higher coercivity of 13130.205 A/m over that of traditional amorphous magnetic films. Complex permeability μ was measured by a microwave network analyzer using the coaxial transmission technique, and double resonance peaks in microwave magnetic permeability were observed in the frequency range of 3.8-5 GHz. This is beneficial for the films to be used as a micro absorber at large bandwidths, resulting in μ'>2.5 in the frequency range of 500 MHz-12 GHz and μ''>6 for 3.6-8 GHz. The experimental results demonstrate that the FeCoB-SiO2 films deposited on flexible substrates have good potential for high frequency applications.