Matching impedance of Cd-substituted magnesium ferrites for wideband and miniaturized antennas

Abstract

The microscale-driven crystal growth and structural tunability of spinel Mg ferrites (Cd0.3Mg0.7Fe2O4) were investigated using various synthesis temperatures (900, 915, 930, 945, and 960 °C) for their application in high-frequency antennas. The results and the crystal structure refinement and morphology analysis, indicate that an increase in the temperature led to changes in the microstructure and enhanced magnetic and dielectric properties. These properties are responsible for the matching impedance. Experimentally, an enhancement of the magnetization with increasing saturation magnetization (38–44 emu/g) and weakened coercivity (113–66 Oe) were observed. A remarkable increase (from 29 to 50) in the real permeability and a slight increase (from 21 to 26) in the permittivity were observed in a broad frequency range from the high to very high frequency bands. Higher temperature synthesis leads to a dense morphology, which enables low magnetic (tan δμ ~10−2) and dielectric losses (tan δε ~10−3), and results in increasing grain sizes (from 0.42 to 0.92 μm) and fewer pores. Predictably, these properties indicate the excellent applicability of these ferrites in miniaturized antennas in the frequency band of the current materials.