Ferrites are ferromagnetic ceramic materials, compounds of iron, boron and barium or strontium or molybdenum. Ferrites have a high magnetic permeability, which allows them to store stronger magnetic fields than iron, and are known as ceramic magnets. They are the most common ordinary radio magnets. The magnetic field B is about 0.35 tesla and the magnetic field strength H is about 30 to 160 kiloampere turns per meter (400 to 2000 oersteds).

Uses

Ferrites are often produced as powder, which can be sintered into solid cores. Ferrite cores are used in electronic inductors, transformers, and electromagnets where the high electrical resistance of the ferrite leads to very low eddy current losses. Early computer memories stored data in the residual magnetic fields of ferrite cores, which were assembled into arrays of core memory. Ferrite powders are used in the coatings of magnetic recording tapes. One such type of material is iron (III) oxide. Ferrite particles are also used as a component of radar-absorbing materials used in stealth aircraft and in the expensive absorption tiles lining the rooms used for electromagnetic compatibility measurements. Most common radio magnets, including those used in loudspeakers, are ferrite magnets. It is common magnetic material for electromagnetic instrument pickups, because of price and relatively high output of resulting pickups. However, such pickups lack certain sonic qualities found in other pickups, such as those that use Alnico alloys or more sophisticated magnets.

Magnetism | Ceramic materials

Ferrite | Ferrite | フェライト磁石