Effect of Magnetization on Magnetic and Dielectric Properties of Co2z/Bam Hexaferrite Composite Materials

Abstract

The phase composition, microscopic morphology, magnetic properties, and dielectric properties of composite ferrites consisting of (1-x) Ba2.8Bi0.2Co2.2Fe22.6Al1.2O41 (Co2Z) and x BaFe12O19 (BaM) with x = 5,10,20,40 wt.% were investigated before and after magnetization. To magnetize the composite ferrite, a soft magnetic phase was combined with a permanent magnetic phase, and the magnetic moment of the former was oriented by the applied magnetic field provided by the latter. The XRD and SEM analyses revealed that the grain size of the composite ferrite was around 1 μm. The actual percentage of BaM phase was higher, which had a diluting effect on the magnetic permeability of the composite ferrites. However, the saturation magnetization strength and coercivity increased with the increase of BaM content. Before magnetization, the relative permeability of the composite ferrites at 1 GHz ranged from 1.65 to 2.40, while it ranged from 1.61 to 2.30 after magnetization. After fitting the magnetic spectrum, it was observed that the equivalent applied field H increased after magnetization, and this increase was equivalent to the increase in anisotropic field of the samples. Moreover, H increased with the increase of BaM content, and the magnetic quality factor of the samples increased from 25~46 before magnetization to 34~102 after magnetization. The relative dielectric constants of the composite ferrites before and after magnetization ranged from 6.76 to 8.26 and 6.42 to 8.77, respectively, with no significant changes. The dielectric loss angle is slightly reduced to about 0.001. The characteristic impedance of Z/5%-40% BaM ferrites is about 0.5, and the miniaturization factor ranges from 4.49 to 3.21. Additionally, these composites have low losses, making them suitable for UHF antenna miniaturization.

Keywords: composite ferrite, low loss, ultra-high frequency, miniaturization