In 1950s, after the discovery of hexagonal ferrites called as hexaferrites, there has been an increasing level of curiosity in hexaferrites and still, it is increasing exponentially. Commercially and technologically, hexaferrites belong to a category of important magnetic materials due to their utilization in various applications such as permanent magnets, recording media, storage devices, rod antennas, high frequency devices, microwave devices etc. There are six types of hexagonal ferrites as M-type, Z-type, Y-type, X-type, U-type and W-type respectively, out of which, the most worldwide manufactured hexagonal ferrite is Barium M-type hexagonal ferrite named as BaM [1]. All categories of hexaferrites shows ferrimagnetic behaviour as their magnetic nature is inherently related to their crystal structure. The current chapter focuses on the classification and structure of hexagonal ferrites. In this book chapter, firstly, we report the six categories of hexaferrites as M, Y, W, X, Z, W and then, we provide a detailed comprehensive review of two approaches called as spinel and S/R/T based model for reporting the structure of hexagonal ferrites respectively. After that, we reported a comprehensive structure of each hexaferrite. Lastly, the concluding remarks have been presented in the current chapter.
