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What Are Permanent Magnets Made From?

Most of the electrons in atoms pair with another electron that occupies the same orbital. These electrons exhibit opposite spins and the small magnetic fields created by the electrons effectively cancel each other out. Some materials, however, contain unpaired electrons. Normally, the spins of these electrons relative to each other orient in random fashion. Permanent magnetism arises in metal oxides and alloys when the electrons in the material, after being subjected to a strong magnetic field, align parallel to each other to induce a much stronger field around the material. Few compounds exhibit strong permanent magnetism.

Ferrites
- The ferrites represent a class of iron-based oxides, some of which exhibit permanent magnetism. The mineral magnetite, Fe3O4, represents the only naturally occurring permanent magnet. Among the synthetic magnetic ferrites, barium iron oxide, BaFe12O19, tends to exhibit the strongest magnetism.
Alnico Alloys
- Alnico alloys contain aluminum, nickel and cobalt in addition to iron. The various compositions of alnico are typically indicated by a Roman numeral; e.g., alnico I, alnico II. The stronger alnico magnets, such as Alnico V, exhibit significantly stronger fields than the ferrite magnets.
Rare-Earth Alloys
- The rare-earth alloys, typified by neodymium-iron-boron--Nd-Fe-B--and samarium-cobalt--Sm-Co--are so named because they contain at least one element from the rare-earth portion of the periodic table of the elements. They tend to possess magnetic fields several times greater than the strongest of the alnico alloys.

Nature