Electronic structure and magnetic properties of Fe@SiO2 soft magnetic composites

Fe@SiO2 soft magnetic composites(SMCs) were prepared via a chemical precipitation method and powder metallurgy technique. Microstructure, electronic structure and magnetic properties were investigated by X-ray diffraction(XRD), transmission electron microscopy(TEM) and first-principles calculation based on density functional theory(DFT). The results show that the eddy current loss Pe of Fe@SiO2 SMCs substantially reduces with the increase of SiO2 coating content. The sample coated with 2 mL ethyl orthosilicate(TEOS) exhibits the best comprehensive magnetic properties with total loss Ps of 132.7 W/kg and the maximum magnetic permeability μm of 55 (20 mT and 200 kHz). The semi-transparent SiO2 coating layer has a uniform, dense, and compact morphology, indicating good adhesion between the SiO2 and the Fe matrix. The Fe/SiO2 interface has good structural stability with an adhesion work (Wad) of about 1.18 J/m2, ascribed to the formation of Fe—O and Fe—Si covalent bonds. The strong hybridization between Fe 3d electrons and O 2p electrons in the range of −4.7 to − 1.6 eV and − 7.5 to − 6.0 eV demonstrates the existence of Fe—O covalent bond. The formation of Fe—Si covalent bond is mainly attributed to the appearance of Si 2s and Fe 3s hybrid states in the low energy region of −9.7 to −8.8 eV. Fe—O and Fe—Si covalent bond can also effectively bind conduction electrons and increase the surface resistivity, which plays an important role in reducing the loss of Fe/SiO2 SMCs. © 2023 Central South University of Technology. All rights reserved.