Ni-Zn ferrites composites with almost equal values of permeability and permittivity for low-frequency antenna design

Composites based on ferrite powders Ni0.95-xZnxCo0.05Fe1.90Mn0.02O4 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 similar to 4.18 to similar 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 epsilon' 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.