Samarium Cobalt Magnet Properties
Sintered SmCo properties defined in FEMM are meant to be representative of typical examples rather than strictly based on the products from one vendor. Reasonable references are the Wikipedia SmCo page and https://www.buntingeurope.com/wp-content/uploads/2018/07/BME_Samarium_Cobalt_data_sheet.pdf.
SmCo magnets come in two formulations:
- SmCo1:5 was the first developed SmCo alloy. Energy products for this alloy range from 16 to 25 MGOe. This alloy has a high electrical conductivity with 20 MS/m being a representative value. Based on manufacturer's specs, a relative permeability 1.03 is typical for this alloy.
- SmCo2:17 is a more recent SmCo alloy. Energy products for this alloy are higher, ranging from 20 to 35 MGOe. Electrical conductivity is lower with 1.16 MS/m being a representative value. Based on manufacturer's specs, a relative permeability 1.1 is typical for this alloy.
Both alloys have a very high coercivity and a straight-line second-quadrant demagnetization curve.
On the basis of data from many vendors, the numerical designation of the magnet grade represents the best-case energy product in units of MGOe as measured at room temperature (20°C) for a range of energy product usually spanning a range of 2 MGOe. However, magnets are rarely delivered magnetized to this best-case magnetization. For this reason, it is assumed that the actual energy product is the numerical grade minus one in units of MGOe, i.e. a SmCo26 magnet has an energy product of 25MGOe at 20°C.
The grades assumed by FEMM are listed below in Tables 1 and 2.
| Grade | \(BH_{max}\), MGOe | \(B_r\), T | \(B_r\), kG | \(H_{cB}\), kA/m | \(H_{cB}\), kOe | \(\sigma\), MS/m |
| SmCo18 | 17 | 0.837 | 8.37 | 647 | 8.13 | 20 |
| SmCo20 | 19 | 0.885 | 8.85 | 684 | 8.59 | 20 |
| SmCo22 | 21 | 0.930 | 9.30 | 719 | 9.03 | 20 |
| SmCo24 | 23 | 0.973 | 9.73 | 752 | 9.45 | 20 |
| Grade | \(BH_{max}\), MGOe | \(B_r\), T | \(B_r\), kG | \(H_{cB}\), kA/m | \(H_{cB}\), kOe | \(\sigma\), MS/m |
| SmCo24 | 23 | 1.006 | 10.06 | 728 | 9.15 | 1.16 |
| SmCo26 | 25 | 1.049 | 10.49 | 759 | 9.53 | 1.16 |
| SmCo28 | 27 | 1.090 | 10.90 | 789 | 9.91 | 1.16 |
| SmCo30 | 29 | 1.130 | 11.30 | 817 | 10.27 | 1.16 |
| SmCo32 | 31 | 1.1679 | 11.68 | 845 | 10.62 | 1.16 |