Hexaferrite

Hexaferrite is a class of ceramic magnetic materials with a hexagonal crystal structure. They are ferrimagnetic oxides characterized by the general formula MFe12O19, where M represents a divalent or trivalent metal cation. Common examples include barium hexaferrite (BaFe12O19) and strontium hexaferrite (SrFe12O19). These materials possess a high Curie temperature, meaning they retain their magnetic properties up to relatively high temperatures, and exhibit strong magnetic anisotropy.

The unique crystal structure of hexaferrites allows for a high density of magnetic moments, leading to a large saturation magnetization and coercivity. This makes them suitable for applications where strong permanent magnets are required. Their production typically involves solid-state reaction methods, where precursor oxides are mixed and calcined at high temperatures. The specific properties of a hexaferrite can be tuned by substituting other metal ions for iron or the M-site cation.

Hexaferrites find widespread use in various technological fields. Their high coercivity and energy product make them ideal for permanent magnets used in electric motors, loudspeakers, magnetic recording media, and magnetic separators. They are also employed in microwave devices due to their specific electromagnetic properties and in shielding applications. The cost-effectiveness and availability of their constituent elements contribute to their popularity in industrial applications.