Rare Earth Magnets: from Samarium-Cobalt to Neodymium Iron Boron

Definition of rare earth magnets?

Rare earth magnets are a group of permanent magnets that essentially consist of ferrous metals (iron, cobalt, more rarely nickel) and rare earth metals (especially neodymium, samarium, praseodymium, dysprosium, terbium, gadolinium). They are characterized in that they simultaneously have a high magnetic remanence flux density Br and a high magnetic coercivity Hc and thus a high magnetic energy density.

sm2co17 magnets (second generation rare earth magnet)
Samarium-Cobalt Magnets
neodymium arc magnets (3rd generation rare earth magnets)
3rd generation RE magnet: Neodymium Magnets

SmCo Magnet: first & second generation of rare earth magnets

Samarium-Cobalt (SmCo) is an alloy of the rare earth metal samarium (Sm) with the metal cobalt (Co). Two crystal structures are suitable as permanent magnets: SmCo5, without additional alloying elements, and Sm2Co17 with iron, copper and zirconium as additional alloying elements. SmCo5 and Sm2Co17 magnets are respectively the 1st and 2nd generations of rare earth permanent magnets. SmCo5 was discovered as a rare earth magnet alloy in 1966 and Sm2Co17 in 1972 by Karl J. Strnat at the U.S. Air Force Materials Laboratory at Wright-Patterson Air Force Base. Sm2Co17 has improved magnetic properties compared to SmCo5, but is more difficult to produce. In the 1970s, Samarium-Cobalt was the material with the highest magnetic energy density until neodymium-iron-boron was discovered.

Neodymium Magnet: third generation of rare earth magnet

Neodymium magnets, also known as NdFeB magnets or neo magnets, are the third generation of rare earth magnet, which were developed in early 1980s independently by General Motors and Sumitomo Special Metals. According to manufacturing process, they are divided into sintered neodymium magnets, plastic bonded neodymium magnets, and hot-pressed neodymium magnets. Sintered neodymium magnets have the highest energy product among all types of permanent magnets.

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