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smco magnets

SmCo Magnets: rare earth permanent magnet

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.

SmCo arc magnets
SmCo arc magnets

Grade (Magnetic Properties) - Sm2Co7 Magnets

Grade Remanence (Br) Intrinsic Coercivity (Hcj) Coercivity (Hcb) Maximum Energy Product (BH)max
kGs kOe kOe MGOe
Max Min Range Range Max Min
YXG20L 9.20 8.60 5-18 4.5-8.8 22 18
YXG22L 9.50 9.00 5-18 4.5-9.2 24 20
YXG24L 10.00 9.50 5-18 4.5-9.7 26 22
YXG26L 10.40 10.00 5-18 4.5-10 27 24
YXG28L 10.80 10.40 5-18 4.5-10.5 28 26
YXG30L 11.10 10.80 5-18 4.5-10.6 30 28
YXG32L 11.40 11.10 5-18 4.5-10.8 31 30
YXG33L 11.60 11.40 5-18 4.5-11.0 32 31
YXG34L 11.80 11.60 5-18 4.5-11.2 33 32
YXG35L 12.20 11.70 5-18 4.5-11.2 35 33
YXG20 9.20 8.60 18-25 7.8-8.8 22 18
YXG22 9.50 9.00 18-25 8.2-9.2 24 20
YXG24 10.00 9.50 18-25 8.6-9.7 26 22
YXG26 10.40 10.00 18-25 9.0-10.0 27 24
YXG28 11.10 10.40 18-25 9.5-10.5 28 26
YXG30 11.10 10.80 18-25 9.8-10.6 30 28
YXG32 11.60 11.10 18-25 10.1-10.8 31 30
YXG33 11.60 11.40 18-25 10.4-11.0 32 31
YXG34 11.80 11.60 18-25 10.6-11.2 33 32
YXG35 12.20 11.70 18-25 10.8-11.5 35 33
YXG20H 9.20 8.60 >25 7.8-8.8 22 18
YXG22H 9.50 9.00 >25 8.2-9.2 24 20
YXG24H 10.00 9.50 >25 8.6-9.7 26 22
YXG26H 10.40 10.00 >25 9.0-10.0 27 24
YXG28H 10.80 10.40 >25 9.5-10.5 28 26
YXG30H 11.10 10.80 >25 9.8-10.6 30 28
YXG32H 11.40 11.10 >25 10.1-10.8 31 30
YXG33H 11.60 11.40 >25 10.4-11.0 33 31
YXG34H 11.80 11.60 >25 10.6-11.2 33 32
YXG35H 12.20 11.70 >25 10.8-11.5 35 33

Sm2Co17 of Low Temp. Coefficient and High Temp. Resistance​

Grade
Sm2Co17
BrHcjHcb(BH)maxMax. Working Temp.Temperature  Coefficient
kGskOekOeMGOeαBr (20℃-150℃)
MaxMinRangeRangeMaxMin%/℃
YXG20LT9.28.6>207.8-8.82218350±0.005
YXG22LT9.59.0>208.2-9.22420350-0.0100
YXG24G10.09.5>208.6-9.72622500-0.0350
YXG22G9.59.0>208.2-9.22424550-0.0350

Manufacture and Applications of SmCo Magnets

SmCo magnets are usually manufactured using powder metallurgy. The alloying elements are first melted in a vacuum induction furnace, quickly cooled and then ground to a particle size of less than 10 µm, at which point only monocrystalline powder is present. The alloy powder is then aligned in a magnetic field and, depending on the process, pressed into a green compact at the same time. This is then followed by a dense sintering process in a vacuum or under protective gas. The magnets obtain their coercive field strength during heat treatment. 

From around 150 to 180°C, SmCo has a higher energy product than neodymium-iron-boron, which is why it is mainly used at higher application temperatures. But the better corrosion resistance, the lower reversible temperature coefficient or the better resistance to ionizing radiation can also make the use of SmCo worthwhile. By alloying the antiferromagnetically behaving gadolinium, the reversible temperature coefficient of the remanence can be reduced to zero or even reversed to positive values.

Due to the higher production costs of SmCo, the economic importance is lower than that of neodymium magnets. The material is used, among other things, in rotating electrical machines with permanent excitation, sensors in automobile construction or in chemical pumps.

About Tengye: Tengye Magnetic supplies finest permanent magnet materials and custom magnetic assemblies to world industry. We work closely with our customer from designing stage to mass production. 

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