A type of strong, permanent magnet made from a rare earth element alloy. Rare earth elements (a.k.a. lanthanides or lanthanoids, the elements from atomic number 57 to 71) are not especially rare, being commonly found in the earth’s crust, nor are they “earths,” which refers to base oxides of electro-positive metals that cannot be smelted or desolved in water. They are highly conductive of electricity and highly reactive and therefore oxidize or tarnish quickly in air. The most common rare earth elements used in magnets include neodymium (actually an alloy of neodymium, iron, and boron) and an alloy of samarium and cobalt.
- Neodymium is the less expensive of the two common types and is the strongest permanent magnet type known. In the music/pro audio world, it is typically used in hard drives, speaker drivers, dynamic microphones, and headphone drivers.
- Samarium-cobalt is more resistant to oxidation and high temperatures than neodymium, and is used in Fender’s SCN (Samarium Cobalt Noiseless) guitar and bass pickups, as well as in high-speed motors, turbo machinery, and in systems that must function in cryogenic or high-temperature environments.