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MAGNETIC PROPERTIES OF SAMARIUM COBALT MAGNETS

Samarium cobalt magnets are part of the rare earth family of magnets and have a maximum energy product range from 15 MGOe to 32 MGOe. There are 11 subgrades of samarium cobalt magnets grouped into two main types, known as samarium cobalt (1-5) and samarium cobalt (2-17). These main groups are given their titles based on their ratio or samarium atoms to cobalt atoms, e.g. the 1-5 range all have one samarium atom per five cobalt atoms. Samarium cobalt (1-5) is the older of the two types and typically has a maximum energy product of 15-24 MGOe and is almost obsolete having generally been superseded in most industrial applications by the more recently developed 2-17 type, which provides a maximum energy product of 22-32 MGOe and a higher maximum operating temperature. Below, you can see a list of all the commercially available samarium cobalt magnet grades and their magnetic properties.

Sm1Co5 (1:5 group of samarium cobalt magnets)

GradeRemanence (BR)
mT
(KGS)
Coercive Force (Hcb)
kA/m
(kOe)
Intrinisc Coercive Force (Hcj)
kA/m
(kOe)
Max. Energy Product (BH) max
kJ/m3
(MGOe)
Max. Operating Temp
TW
SmCo16 810-850
(8.1-8.5)
660
(8.3)
1830
23
110-127
(14-16)
250°C
SmCo18 850-900
(8.5-9.0)
700
(8.8)
1830
(23)
127-143
(16-18)
250°C
SmCo20 900-940
(9.0-9.4)
725
(9.1)
1830
(23)
150-167
(19-21)
250°C
SmCo22 920-960
(9.2-9.6)
750
(9.4)
1830
(23)
160-175
(20-22)
250°C
SmCo24 960-1000
(9.6-10.0)
770
(9.7)
1830
(23)
175-190
(22-24)
250°C
SmCo18S 850-900
(8.5-9.0)
700
(8.8)
2000
(25)
135-151
(17-19)
250°C
SmCo20S 900-940
(9.0-9.4)
725
(9.1)
2000
(25)
143-160
(18-20)
250°C
SmCo22S 920-960
(9.2-9.6)
750
(9.4)
2000
(25)
160-175
(20-22)
250°C

 

Sm2Co175 (2:17 group of samarium cobalt magnets)

GradeRemanence (BR)
mT
(KGS)
Coercive Force (Hcb)
kA/m
(kOe)
Intrinisc Coercive Force (Hcj)
kA/m
(kOe)
Max. Energy Product (BH) max
kJ/m3
(MGOe)
Max. Operating Temp
TW
SmCo24L 950-1020
(9.5-10.2)
716
(9.0)
955
(12)
175-191
(22-24)
350°C
SmCo26L 1020-1050
(10.2-10.5)
748
(9.4)
955
(12)
191-207
(24-26)
350°C
SmCo28L 1030-1080
(10.3-10.8)
765
(9.9)
955
(12)
207-220
(26-28)
350°C
SmCo30L 1080-1150
(10.8-11.5)
795
(10.0)
955
(12)
220-240
(28-30)
350°C
SmCo32L 1100-1150
(11.0-11.5)
810
(10.2)
955
(12)
230-255
(22-24)
350°C
SmCo26M 1020-1050
(10.2-10.5)
780
(9.8)
1273
(16)
191-207
(24-26)
350°C
SmCo28M 1030-1080
(10.3-10.8)
796
(10.0)
1273
(16)
207-220
(26-28)
350°C
SmCo30M 1080-1100
(10.8-11.0)
835
(10.5)
1273
(16)
220-240
(28-30)
350°C
SmCo32M 1100-1130
(11.0-11.3)
845
(10.6)
1273
(16)
230-255
(29-32)
350°C
SmCo26 1020-1050
(10.2-10.5)
780
(9.8)
1434
(19)
191-207
(24-26)
350°C
SmCo28 1030-1080
(10.3-10.8)
796
(10.0)
1435
(20)
207-220
(26-28)
350°C
SmCo30 1080-1100
(10.8-11.0)
835
(10.5)
1436
(21)
220-240
(28-30)
350°C
SmCo32 1100-1130
(11.0-11.3)
845
(10.6)
1194
(15)
230-255
(29-32)
350°C
SmCo24H 950-1020
(9.5-10.2)
750
(9.4)
1990
(25)
175-191
(22-24)
350°C
SmCo26H 1020-1050
(10.2-10.5)
780
(9.8)
1990
(25)
191-207
(24-26)
350°C
SmCo28H 1030-1080
(10.3-10.8)
796
(10.0)
1990
(25)
207-220
(26-28)
350°C
SmCo30H 1080-1100
(10.8-11.0)
835
(10.5)
1990
(25)
220-240
(28-30)
350°C

No other rare earth magnetic material can match the performance or magnetic stability of samarium cobalt at high temperatures and the Sm2Co17 series will maintain their performance in temperatures up to 350 degrees Celsius, while the weaker Sm1Co15 grades have a lower maximum operating temperature of 250 degrees Celsius. Samarium cobalt magnets experience minimal change in their magnetic performance as temperature increases from ambient, far less than neodymium and ferrite (ceramic) magnets. Although the geometry of a magnet, and the application in which it is used also effects how a magnet behaves at high temperature it is a general rule that samarium cobalt magnets will outperform all others once the temperature exceeds 150 degrees Celsius.

Samarium cobalt can be manufactured with the same array of coatings as neodymium magnets and as standard, we coat our samarium cobalt magnets with a triple layer of nickel, copper, nickel. However, because of their resistance to corrosion it is not uncommon to use uncoated samarium cobalt magnets as the coating does not necessarily provide any notable resistance. The 1:5 series does not contain any iron, which is the reason they are so resistant to corrosion while the 2:17 series contains traces of iron which can result in surface corrosion if not coated and used in moist environments. A limitation of samarium cobalt magnets is their physical strength; they are particularly brittle and will fracture if subjected to impact or stress.

Because of their stability, temperature coefficient and resistance to corrosion samarium cobalt magnets are often used in sensors, high temperature motors, generators and marine applications. If you require advice about using samarium cobalt magnets for a particular application then contact or experts today who will be happy to help on 0845 5194701.