Rare-earth magnet

Ferrofluid on glass,[1] with a rare-earth magnet underneath

Rare-earth magnets are strong permanent magnets made from alloys of rare earth elements.[2]

Developed in the 1970s and '80s, rare-earth magnets are the strongest type of permanent magnets made. They have much stronger magnetic fields than other types such as ferrite or alnico magnets.

There are two types: neodymium magnets and samarium-cobalt magnets. Some rare-earth magnets such as Terfenol-D are magnetostrictive.[3] They also have uses e.g. in speakers.

Rare earth magnets are extremely brittle and also vulnerable to corrosion, so they are usually plated or coated to protect them from breaking, chipping, or crumbling into powder.[4]

References

  1. ↑ Ferrofluid: a liquid that becomes strongly magnetized in the presence of a magnetic field.
  2. ↑ McCaig, Malcolm 1977. Permanent magnets in theory and practice. New York: Wiley. ISBN 0-7273-1604-4
  3. ↑ Magnetostrictive materials change their shape or dimensions during the process of magnetization
  4. ↑ Furlani, Edward P. 2001. Permanent magnet and electromechanical devices: materials, analysis and applications. Academic Press Series in Electromagnetism. ISBN 0-12-269951-3