Definition of a Rare-Earth Magnet

Features of Rare-Earth Magnets

• Rare-earth magnets are composite alloys, including elements from the Lanthanide group. Common alloys include neodymium-iron-boron (NdFeB) and samarium-cobalt (SmCo). Neodymium magnets are typically more powerful, while samarium magnets are well-suited to high temperature applications.

Significance of Rare-Earth Magnets

• Rare-earth magnets are used in numerous electronic, commercial and industrial applications including electromotors, generators, speakers, cell phones and magnetic toy building sets.

Two Types of Rare-Earth Magnets

• Sintered forms have more magnetic strength, but are costly, and often brittle. Bonded forms have less magnetic strength, but are less expensive and more durable.

Identification of Rare-Earth Magnets

• To prevent corrosion and breakage, manufacturers usually coat rare-earth magnets with nickel or copper alloys; this gives them a shiny silver or gold appearance that differs from the flat gray or black of ferrite magnets.

Expert Insight

• Magnetic strength is referred to as the Maximum Energy Product and is expressed in millions Gauss Oersted (MGoe). For example, neodymium rare-earth magnets may have Maximum Energy Products of 40 to 52 MGoe, while ferrite magnets more typically exhibit Maximum Energy Products of 1 to 4 MGoe.