Why are ferrites usually hard and brittle materials?

Ferrites are classified as ceramics, and their characteristic hardness and brittleness are inherent to the chemical bonding and crystalline structures typical of this material class.

As inorganic, nonmetallic solids, ceramics generally possess strong atomic bonds that contribute to their hardness and resistance to wear. However, these same rigid structures lack the ability to deform plastically under stress, which results in their characteristic brittleness. While the term "hard" in the context of magnetic ceramics can sometimes refer to magnetic properties—specifically the difficulty of changing the direction of magnetization in materials like hexagonal or garnet ferrites—the physical hardness and brittleness of ferrites as materials are fundamentally linked to their ceramic nature, which includes their polycrystalline structure and the nature of their chemical bonding.123