Ferrites are ferromagnetic ceramic materials, compounds of iron, boron and barium or strontium. Ferrites have a high magnetic permeability, which allows them to store stronger magnetic fields than iron. Ferrites are often produced as powder, which can be sintered into solid cores. Ferrite cores are used in electronic inductors and electromagnets. Early computer memories stored data in the 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 ferric oxide.