High Magnetic Loss Mg–Cu Ferrites for Ultrahigh Frequency EMI Suppression Applications

Mg_1-xCu_xFe₂O₄ ferrites for electromagnetic interference suppression were systematically investigated in crystallographic structure, morphologies, and magnetic and dielectric spectra over a frequency range of 10-1000 MHz. Findings indicated that the Mg_1-xCu_xFe₂O₄ ferrites with x= 0-0.6 showed a single-phase cubic spinel structure, but the sample structure with x = 0.8 transforms into a tetragonal phase. Moreover, the substitution of Cu was shown to lower the sintering temperature and enhance densification of the ferrites, resulting in increased saturation magnetization (67%) and decreased coercivity (88%). More importantly, the complex permeability and permittivity of Mg-Cu ferrites could be tailored with Cu content, leading to an enhanced magnetic loss and permeability. The magnetic loss tangent of the Mg_0.4Cu_0.6Fe₂O₄ ferrite sintered at 1150°C was significantly increased by 56% at f > 300 MHz.