Samarium Cobalt Magnets

Samarium cobalt magnets are becoming an ideal choice for high-temperature and high-reliability applications due to their excellent temperature stability, corrosion resistance, and high magnetic performance.

Definition of Samarium Cobalt Magnets

Samarium cobalt magnets are composed of the rare earth element samarium (Sm) and the transition metal cobalt (Co). There are two common crystal structure types: the 1:5 type (SmCo₅) and the 2:17 type (Sm₂Co₁₇). Among these, the 2:17 type is preferred in high-temperature environments due to its higher magnetic energy product (up to 35 MGOe) and outstanding temperature and corrosion resistance.

Advantages of Samarium Cobalt Magnets

| Strong Corrosion and Oxidation Resistance: Naturally exhibiting excellent resistance to corrosion and oxidation, samarium-cobalt magnets do not require additional coating for protection. They can work stably in harsh environments such as humid or chemically corrosive conditions, reducing maintenance costs.

| Excellent High-Temperature Performance: The maximum operating temperature can reach 250-350°C, far exceeding that of neodymium-iron-boron magnets (generally no more than 200°C). The wonderful performance means that in high-temperature environments, their magnetic performance remains stable, making them suitable for aerospace, industrial motors, and other temperature-sensitive applications.

| Stable Magnetic Performance: They have an extremely low temperature coefficient, meaning the magnetic flux density is minimally impacted by temperature changes, ensuring consistent magnetic performance in various environments. This makes them suitable for precision-sensitive devices such as sensors and precision instruments.

Types of Samarium Cobalt Magnets

Samarium-cobalt permanent magnets are mainly composed of metallic samarium (Sm), metallic cobalt (Co), copper (Cu), iron (Fe), zirconium (Zr), and other elements. They can be structurally divided into the 1:5 type and the 2:17 type.

2:17 Type Samarium Cobalt

The 2:17 type samarium-cobalt magnet, also known as Sm₂Co₁₇, has a maximum magnetic energy product range of 20-35 MGOe and an operating temperature of up to 500°C. It features a lower temperature coefficient and better corrosion resistance.

1:5 Type Samarium Cobalt

The 1:5 type samarium-cobalt magnet, also referred to as SmCo₅, has a maximum magnetic energy product range of 16-25 MGOe and an operating temperature of up to 250°C. Although its maximum magnetic energy product is lower than that of the 2:17 type, it offers better mechanical properties and ductility.

Comparison of Sm₂Co₁₇ and SmCo₅

| Different Components： The SmCo 1:5 magnet, known as SmCo₅, primarily consists of samarium, cobalt, and praseodymium, or it may just contain pure samarium-cobalt. The SmCo 2:17 magnet, known as Sm₂Co₁₇, mainly contains samarium, cobalt, copper, iron, and zirconium.

| Different Physical Properties: The maximum operating temperature of SmCo₅ is 250°C, while that of Sm₂Co₁₇ is 350°C. Compared to Sm₂Co₁₇, SmCo₅ is more brittle and easier to process.

| Machinability: The magnetic energy product of SmCo₅ is lower than that of Sm₂Co₁₇; however, its machinability is better, making it suitable for machining special-shaped components. Sm₂Co₁₇ can achieve a magnetic energy product of 28 MGOe, exhibiting excellent magnetic performance and a larger current usage.

Samarium Cobalt Magnet Grades

Composite	Grade	Residual Induction/BR (Gauss)	Coercive Force/Hc (Oe)	Intrinsic Coercive Force/Hci (Koe)	Max.Energy Product/Bhmax (MGOe)	Maximum Operating Temp(°C/°F)
Sm1Co5	16	8100	7800	15	16	127/260
Sm1Co5	18	8500	8300	15	18	143/289
Sm1Co5	20	9000	8500	15	20	167/332
Sm1Co5	22	9200	8900	15	22	175/347
Sm1Co5	24	9600	9200	15	24	190/374
Sm1Co5	16S	7900	7700	23	17	135/275
Sm1Co5	18S	8400	8100	23	19	151/303
Sm1Co5	20S	8900	8600	23	21	167/332
Sm1Co5	22S	9200	8900	23	23	183/361
Sm1Co5	24S	9600	9300	23	25	199/390
Sm1Co5	10X	6200	6100	23	11	88/190
Sm2Co17	24L	9500	6800	8--12	24	191/375
Sm2Co17	26L	10200	6800	8--12	26	207/404
Sm2Co17	28L	10500	6800	8--12	28	220/428
Sm2Co17	30L	10800	6800	8--12	30	240/464
Sm2Co17	32L	11000	6800	8--12	32	255/491
Sm2Co17	26M	10200	8500	12--18	26	207/404
Sm2Co17	28M	10500	8500	12--18	28	220/428
Sm2Co17	30M	10800	8500	12--18	30	240/464
Sm2Co17	32M	11000	8500	12--18	32	255/491
Sm2Co17	24	9500	8700	18	24	191/375
Sm2Co17	26	10200	9400	18	26	207/404
Sm2Co17	28	10500	9700	18	28	220/428
Sm2Co17	30	10800	9900	18	30	240/464
Sm2Co17	32	11000	10200	18	32	255/491
Sm2Co17	24H	9500	8700	25	24	191/375
Sm2Co17	26H	10200	9400	25	26	207/404
Sm2Co17	28H	10500	9700	25	28	220/428
Sm2Co17	30H	10800	9900	25	30	240/464
Sm2Co17	32H	11000	10200	25	32	255/491
Sm2Co17	22X	9400	8400	15-20	22	175/347

Applications of Samarium-Cobalt Magnets

Due to their excellent magnetic performance, high-temperature stability, and corrosion resistance, samarium-cobalt magnets are widely applied in various fields. The main applications include:

| Aerospace: Used in aerospace electric motors, such as auxiliary drive motors for gas turbines and servo motors, ensuring stable operation in high-temperature and high-vibration environments.

| High-Temperature Motors and Industrial Equipment: Used in petrochemical drilling motors to ensure reliable operation in high-temperature and corrosive environments.

Employed in high-speed rail traction motors to provide a strong magnetic field output, supporting frequent start-stop operations and long-duration runs.