SmCo Magnets' Composition, Series and Types

Besides the NdFeB magnets, the SmCo magnet is another type of Rare-earth magnet mainly composed of Samarium-Cobalt alloys. A SmCo magnet may have a magnetic strength comparable to that of a NdFeB one, but is higher in temperature rating and coercivity. SmCo magnets are available in two series defined by the ratio of Samarium to Cobalt: Series1-5 (SmCo₅) and Series 2-17 (Sm₂Co₁₇).

SmCo5

These magnets are composed of Samarium-Cobalt alloys with Sm-Co ratio of 1-5, that is to say, one atom of Samarium with five atoms of Cobalt. By weight the Samarium would occupy 36% of the total. By weight this samarium cobalt magnet alloy will typically contain 36% Samarium with the balance Cobalt. This series of SmCo magnet is able to provide Max. Energy Product of 25 MGOe and has a reversible temperature coefficient of -0.05%/°C. In addition, this series is easier to calibrate to a specific magnetic field than the Sm₂Co₁₇ series.

Sm2Co17

This series is composed of Samarium-Cobalt alloys with SmCo ratio of 2 to 17, that is to say, 2 Samarium atoms with 17 Cobalt atoms. It also contains other elements such as iron, copper, Zirconium, Hafnium but in very small quantities. By weight the Samarium occupies about 25% of the total. This type has a higher Max. Energy Product of 32 MGOe and a reversible temperature coefficient of -0.03%/°C.

Types

Currently in the magnet market two types of SmCo magnets are available: the bonded type and the sintered type.

Bonded SmCo magnets

The bonded SmCo magnets are anisotropic ones manufactured with magnet powder held in place by epoxy resins or other special "binders". Energy products of the bonded magnet range from 5 MGOe to 15.1 MGOe.

Sintered SmCo magnets

Sintered SmCo magnets are generally manufactured through this process: alloy milling to fine powder-powder pressed-magnetic fields applying-sintering in special furnace-grounding and shaping-coating.

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