Samarium Cobalt (SmCo) is the other Rare Earth magnet! SmCo is the alternative to Neodymium magnets when a more stable output over a much wider temperature range is required.
Sintered Samarium Cobalt rare-earth (SmCo) magnets are manufactured by using powder metallurgy techniques which include stringent process controls and complicated heat treatment cycles. The composition of this alloy is approximately 35% Samarium, 60% cobalt with the balance being Fe & Cu. By varying the percentages of this composition and changing the sintering & heat treatment cycles the two grades 1:5 & 2:17 are produced. The difference between them is in energy product, temperature coefficient and magnetisation force required tosaturate. The 2:17 offers a better performance & lower temperature coefficient, however it is slightly more expensive and requires very high fields to magnetise it.
The SmCo magnets can be used from temperatures nearly as low as absolute zero (-273°C) up to +350°C. Although Neodymium magnets provide stronger fields at room temperature, SmCo starts to outperform at temperatures above +150°C.
The 2:17 grade is the most popular and is readily available from stock in a disc or block format. Non standard sizes can be sliced or ground at short notice to suit customers' dimensional specifications. Being extremely brittle, great care must be taken when handling magnetised Samarium Cobalt to prevent personal injury or damage to the magnets.
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With superior temperature coefficients than Neodymium, magnetic output from SmCo varies less over a change in temperature, making it an ideal choice for temperature sensitive applications such as sensors and loudspeakers where stability of the field during operation is important. SmCo also has a very good intrinsic coercivity allowing it to be used in applications where high external demagnetising forces may be present, such as the starting of an electric motor.
SmCo has very little free iron in its structure meaning it offers excellent corrosion resistance to water. It very rarely requires protective coating. Because of its performance characteristics SmCo is often used instead of Neodymium in mission critical applications such as aerospace and military applications. SmCo is a brittle material and could break, chip, snap or possibly even shatter if mishandled. Care should be taken when assembling with the SmCo.