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Why are Samarium Cobalt and Neodymium Magnets Called “Rare Earth” Magnets?

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rare-earth-elementsThere are seventeen rare earth elements– fifteen of which are lanthanides and two of which are transition metals, yttrium and scandium, that are found with lanthanides and are chemically similar. Samarium (Sm) and Neodymium (Nd) are the two most commonly used rare earth elements in magnetic applications. More specifically, Samarium and Neodymium are light rare earth elements (LREE) in the cerium earths group. Samarium Cobalt and Neodymium alloy magnets provide some of the best force-to-weight ratios for industrial and commercial applications.

The rare earth elements are typically found together in the same mineral deposits, and these deposits are plentiful. With the exception of promethium, none of the rare earth elements are especially rare. For example, samarium is the 40th most plentiful element found in the Earth’s mineral deposits. Neodymium, like other rare earth elements, occurs in small, less accessible ore deposits. However, this rare earth element is nearly as common as copper and more plentiful than gold.

In general, rare earth elements were given their name for two different, yet significant reasons. The first possible naming derivation relies on the initial perceived scarcity of all seventeen rare earth elements. The second suggested etymology stems from the difficult process of separating each rare earth element from its mineral ore.

neodymium-rectangle-transThe relatively small and difficult to access ore deposits containing rare earth elements contributed to the initial naming of the seventeen elements. The term “earths” simply refers to naturally occurring mineral deposits. The historical scarcity of these elements made its namesake inevitable. Currently, China meets approximately 95% of global demand for rare earths – mining and refining around 100,000 metric tons of rare earths a year. The United States, Afghanistan, Australia, and Japan also have significant rare earths reserves.

The second explanation for rare earth elements being designated “rare earth” was due to difficulty in both the mining and refining processes, which was typically done by crystallization. The term “rare” is historically synonymous with “difficult.” Because their mining and refining processes were not simple, some experts suggest the term “rare earth” was applied to these seventeen elements as a result.

samarium-cobalt-array-smSamarium Cobalt magnets and Neodymium rare earth magnets are neither prohibitively expensive nor in short supply. Their label as “rare earth” magnets should not be a primary reason to either select or discount these magnets from industrial or commercial applications. Potential use of either of these magnets should be carefully measured according to intended usages, and according to variables like heat tolerances. The designation of magnets as “rare earth” also allows for a general categorization of both SmCo magnets and Neo magnets together when mentioned alongside traditional Alnico magnets or Ferrite magnets.

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Alnico has the highest operating temperature of all magnet materials (up to 930°F/500°C.)

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