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

Abstract

Spinel ferrites have been extensively used in the design and implementation of electromagnetic interference (EMI) suppressors and EM wave absorption materials in the megahertz frequency range. It is well known that EMI absorbing magnetic materials require high initial permeability and loss factor. MnZn and NiZn spinel ferrites are often used in the lower frequency range (< 300 MHz) due to the limit of Snoek's law. Therefore, it is of scientific and technological importance to explore new materials with high EMI suppression performances in the ultra-high frequency range (UHF, 300 MHz-1 GHz). Recently, Mg-Cu ferrites have received attention due to their attractive magneto-dielectric properties and high-density polycrystalline growth at relatively low temperatures. Either complex permeability or permittivity is sensitive to chemical composition, sintered density and the microstructure. Control of the process makes it possible to achieve high permeability and large loss factor simultaneously in Mg-Cu ferrites for high performance EMI suppression. In this study, the influences of Cu as a substitute for Mg and sintering temperature upon microstructure and high frequency properties of Mg-Cu ferrites were investigated for their ability to suppress EMI.