Ni-Zn Ferrites Composites With Almost Equal Values of Permeability and Permittivity for Low-Frequency Antenna Design

Composites based on ferrite powders Ni_0.95-xZnxCo_0.05Fe_1.90Mn_0.02 O₄ with x=0-0.25, with a volume concentration of 50%, were fabricated and characterized. Dielectric and magnetic properties of the composites were measured over 0.01-16.5 GHz. The permeability of the composites at low frequency increases from ~4.18 to ~7.85 as the contribution of Zn is increased from x=0 to x=0.25, while the permittivity remains almost unchanged with x. The composites based on the ferrite powders with Zn of x=0.10-0.25 have almost equal values of epsiv´ and mu´ at low frequency (<30 MHz). With the low magnetic and dielectric loss tangent, these materials are useful to the design of miniaturized antennas over 2-30 MHz