Rare-Earth Magnets Intro.

Rare earth magnets are magnets composed of alloys of the Lanthanide group of elements. The two Lanthanide elements most prevalent in the production of permanent magnets are Neodymium and Samarium. There are numerous alloy formulations of rare earth magnets covered under many different patents but the most common commercial varieties are Neodymium-Iron-Boron (NdFeB) and Samarium Cobalt (SmCo). Neodymium-Iron-Boron magnets are the most advanced commercialized permanent magnet material available today.

Rare earth magnets are available in sintered and bonded forms. Sintered magnets are a type of ceramic composed of the compressed powder of the alloy material being used. Sintering involves the compaction of fine alloy powder in a die and then fusing the powder into a solid material. While the sintered magnets are solid, their physical properties are more similar to a ceramic and are easily broken and chipped. Bonded magnets use a polymer base to hold the alloy powder together. The energy product of bonded magnets is much lower than that of the sintered magnets. Sintered NdFeB magnets are generally plated or coated with a material to prevent corrosion. There are various coatings available.