Hexaferrite composites with sintering-induced texture for Snoek's product enhancement and magnetic loss suppression

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Hexaferrites with high permeability and low magnetic loss have been attracting great attention from both academic and industrial communities as promising high-frequency materials for modern communication applications. The magnetic properties of hexaferrites are closely related to the crystallographic texture and can be improved by orienting the crystallites. The traditional magnetic field orientation technique, however, has the disadvantages of complicated process and low efficiency. Here, a tunable crystallographic texture of polycrystalline hexaferrite composites achieved by a non-magnetic-field orientation technique is reported. Tabular Co2Z hexaferrite crystallites are synthesized from BaM and Co2Y hexaferrite mixtures and oriented in a form of lamination during the grain growth stage of the sintering process. These layered grains with paralleled easy-magnetization planes play an important role in enhancing the magnetic permeability and suppressing the eddy current from penetrating highly insulating grain boundaries at high frequencies. The textured hexaferrite composite with optimized composition exhibits a high permeability of 16.6, low magnetic specific loss of 0.006, and enhanced Snoek's product of 17.4 GHz at 200 MHz. These results demonstrate an easy and effective method to achieve textured hexaferrite composites without magnetic fields and reveal the potential of hexaferrite composites with sintering-induced texture for high-frequency low-loss magnetic applications.