Rare earth magnets are not made from rare materials. The metals that make rare earth magnets are commonly found, such as lead or tin. They have a strong permanent magnetic field that surpasses that of ferrite and alnico magnets. Neodymium magnets and samarium-cobalt magnets are the two available types of rare earth magnets.
Neodymium magnets were invented in 1982 by General Motors and Sumitomo Special Motors. They are the strongest yet the least expensive of the two types and consequently, the magnet with the most applications. The samarium-cobalt magnet was the first type of permanent magnet invented. Although weaker, they are also more costly. The greatest benefit from using samarium-cobalt magnets are there high Curie-temperature. This magnet is used almost exclusively where high operating temperatures are used.
Both magnets are brittle and prone to breakage and both are highly susceptible to corrosion. The samarium-cobalt magnet is also easily fractured when exposed to thermal shock. Both rare earth metals owe their magnetic strength to their crystalline structures that have very high magnetic anisotropy, or are easily magnetized in one direction. Their atoms can retain high magnetism and stability which contributes to their strength.
All rare earth magnets can be hazardous when handled carelessly. Bones have been broken when sandwiched between two rare earth magnets and lives have been lost as a result of swallowing these magnets. They need to be regarded as dangerous enough to handle cautiously. Despite their potential for danger, they are used successfully in computer hard drives, cordless tools, electric car engines, and self powered flashlights to name just a few of the current applications. These magnets have proven that they can serve man-kind in countless ways and new inventions using their magnetic capabilities are sure to be developed.