What Are Samarium Cobalt Magnets
Samarium cobalt (SmCo) magnets are a type of rare-earth magnet made from an alloy of samarium (Sm) and cobalt (Co). These magnets are known for their excellent magnetic properties, including high energy density, resistance to high temperatures, and strong magnetic strength. SmCo magnets are typically used in applications where high performance and reliability are required, such as in electric motors, sensors, medical devices, and aerospace equipment.
There are two main types of SmCo magnets:
1. SmCo-1 (SmCo 1:5) – Composed of 1 part samarium to 5 parts cobalt, offering high coercivity and resistance to demagnetization.
2. SmCo-2 (SmCo 2:17) – Composed of 2 parts samarium to 17 parts cobalt, offering even higher energy density and greater temperature stability.
They are particularly valued for their ability to withstand extreme conditions, including high temperatures (up to about 350°C), corrosion resistance (without needing additional coatings), and strong magnetic fields, making them ideal for critical and demanding applications.
History:
Introduced in the 1970s, samarium cobalt magnets were the first commercially available rare-earth magnets. Their introduction was revolutionary, tripling the maximum energy product of any other magnet available at the time. Prior to the introduction of the samarium cobalt magnet the standard in magnetics was the Alnico alloy magnet. Samarium cobalt magnets held their place as the strongest magnets until their increasing production costs led engineers to search for a cheaper alternative and the neodymium magnet was formulated, now the strongest magnets in the world.
Did you know? Samarium cobalt magnets were the first rare-earth magnets commercially available.
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CHEMICAL MAKEUP
The most commonly used grade of samarium cobalt magnet is made from an alloy which is around 35% samarium (Sm) and 60% cobalt (Co) with small amounts of iron (Fe), copper (Cu), hafnium (Hf), zirconium (Zr) and praseodymium (Pr). Some grades of samarium cobalt magnets are made purely from samarium and cobalt and these have excellent resistance to corrosion.
STRENGTHS
Samarium cobalt magnets are not as powerful as super-strong neodymium magnets but they have some significant advantages. Samarium cobalt magnets work over a wider temperature range, have superior temperature coefficients and have much greater corrosion resistance. Samarium cobalt magnets certainly come into their own at high operating temperatures and will begin to outperform special high-temperature neodymium magnets from 150oC. However, regular neodymium magnets have a maximum operating temperature of 80oC.
Samarium cobalt magnets do not just excel at high temperatures, they maintain their magnetic properties even at temperatures below absolute zero (-273 oC) making them popular for cryogenic applications.
Did you know? Samarium cobalt magnets can even be used in temperatures as low as -273 oC (known as absolute zero). That’s mighty cold!
As most grades of samarium cobalt contain little or no iron, this gives them an excellent resistance to corrosion whereas neodymium magnets typically contain 60-75% iron. Samarium cobalt magnets, like neodymium magnets, provide a lot of magnetic strength (although not as much as neodymium magnets) when compared to their size and because they are rare-earth magnets they have an extremely high-resistance to demagnetisation from external magnetic fields.
On the downside samarium cobalt magnets can be expensive when compared to neodymium magnets due to the cost of producing cobalt. As with other rare-earth magnets, they are also very brittle and are therefore best used in applications where direct impact is not required.
Samarium cobalt magnets, because of their characteristics are most commonly used in applications which require high operating temperatures such as generators, pump couplings, sensors, motors, marine applications and in the automotive, aerospace, military and food and manufacturing industries.