A ferrite is a ceramic material made by mixing and firing large proportions of iron(III) oxide (Fe2O3, rust) blended with small proportions of one or more additional metallic elements, such as barium, manganese, nickel, and zinc. They are electrically nonconductive, meaning that they are insulators, and ferrimagnetic, meaning they can easily be magnetized or attracted to a magnet. Ferrites can be divided into two families based on their resistance to being demagnetized (magnetic coercivity).
Hard ferrites have high coercivity, so are difficult to demagnetize. They are used to make permanent magnets for applications such as refrigerator magnets, loudspeakers, and small electric motors.
Soft ferrites have low coercivity, so they easily change their magnetization and act as conductors of magnetic fields. They are used in the electronics industry to make efficient magnetic cores called ferrite cores for high-frequency inductors, transformers and antennas, and in various microwave components.
Ferrite compounds are extremely low cost, being made of mostly rusted iron (iron oxide), and have excellent corrosion resistance. They are very stable and can be made with both high and low coercive forces. Yogoro Kato and Takeshi Takei of the Tokyo Institute of Technology synthesized the first ferrite compounds in 1930.