Consequences of magnetic anisotropy in realizing practical microwave hexaferrite devices

With the rapidly growing demand for bandwidth in wireless communication systems and increasing frequencies of operation of electronic devices, in recent years resurgence in scientific interest in highly anisotropic hexagonal ferrites has been noted. This interest stems in part from a number of emerging applications that pose significant materials challenges that cannot be addressed using traditional rf and microwave ferrite materials. In this manuscript, several specific applications that could benefit from the unique properties of hexagonal ferrites are discussed. Fundamental principles of operation, materials requirements, as well as unique device design and modeling challenges are reviewed. Applications of textured magnetically uniaxial hexagonal ferrite composites in microwave and mm-wave non-reciprocal ferrite control devices are discussed. Applications of textured magnetically planar hexagonal ferrite composites as antenna and electronic bandgap metamaterial substrates, rf inductors and transformers, and electromagnetic interference suppression devices are reviewed. Suggestions on directions for future research and development are provided.