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Magnetic properties of sol-gel and conventional ceramic processed Ba3Co2Fe2O41 hexaferrite were investigated and compared for terrestrial digital multimedia broadcasting (T-DMB) antenna application. All of the synthesized powder and sintered body showed almost single Z-phase. The loss tan δ of sol-gel processed and sintered Co2Z hexaferrite was 0.010 at 200 MHz, while conventional ceramic processed and sintered Co2Z showed 0.068. The ωd (resonance frequency of domain wall) and ωs (resonance frequency of spin components) of sol-gel and ceramic processed hexaferrites were estimated to be 10 and 1160 MHz and 17 and 1025 MHz, respectively. The frequency difference between ωd and ωs (1150 MHz) for the sol-gel processed hexaferrite is wider than that (1008 MHz) for the ceramic processed hexaferrite. The permeabilities of sol-gel and ceramic processed hexaferrites were 6.91 and 9.23 at 200 MHz, respectively. Both permeabilities are higher than 6.88 and 7.64 of corresponding permittivities at the same frequency, respectively. It is found that the sol-gel processed and sintered Z-type hexaferrite meet desired low-loss tan δ and broadband for T-DMB antenna.

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Low magnetic and dielectric loss Co2Z (Ba3Co2Fe24O41)–glass composite in the frequency range of 1–3 GHz is reported. Co2Z–glass composite was prepared by firing a mixture of 40 h shake-milled Co2Z hexaferrite powder and borosilicate glass at 950 °C for 1 h. The real part of permeability decreased slightly from 2.29 to 1.96 at 2.4 GHz as the glass content increased from 0 to 4 wt. %, but magnetic loss decreased less than 0.02. On the other hand, the real part of permittivity was 7.29 at 0 wt. % and 7.28 at 4 wt. % glass and dielectric loss was less than 0.01 at 2.4 GHz. The 3D peak gain of Co2Z–glass composite chip antenna was measured to be 3.32 dBi at 2.35 GHz. These results imply that the Co2Z–glass composite is an underpinning magnetodielectric material for gigahertz antenna applications.