Samarium Cobalt (SmCo) disc magnets are powerful magnets rare earth magnets composed of samarium and cobalt. They are commonly used in high performance motors, magnetic couplings and magnetic separators. These are brittle magnets and are prone to cracking and chipping. Samarium magnets can be used for high temperature applications where neodymium will not work.
Corrosion Resistance
SmCo magnets can usually be used in humid applications without any need for a protective coating. In wet envrironments, coating of SmCo(2:17) in NiCuNi is recommended to avoid surface corrosion issue.
The corrosion resistant of SmCo magnets are considered good, surface coating is unnecessary, but the coatings like NiCuNi, Zn, Black epoxy can be plated if required. The oxidation resistance behavior of SmCo (2:17)-type high-temperature magnets modified with Ni–Cr two-layer coating is under studied.
Excellent Temperature Stability
Samarium cobalt magnets experience a minimal change in their magnetic performance as temperature increases from ambient, far less than neodymium and ferrite (ceramic) magnets. Being part of the rare-earth magnet family, Samarium cobalt magnets rank similarly in strength to neodymium magnets but have much higher temperature stability and higher coercivity.
| Physical properties of sintered Sm-Co magnets | |
| Property (unit) | Sm-Co |
| Remanence (T) | 0.8–1.16 |
| Coercivity (MA/m) | 0.493–2.79 |
| Relative permeability (–) | 1.05–1.1 |
| Temperature coefficient of remanence (%/K) | −0.03..–0.05 |
| Temperature coefficient of coercivity (%/K) | −0.15..–0.30 |
| Curie temperature (°C) | 700–850 |
| Density (g/cm3) | 8.2–8.5 |
| CTE, magnetizing direction (1/K) | (5–9)×10−6 |
| CTE, normal to magnetizing direction (1/K) | (10–13)×10−6 |
| Flexural strength (N/mm2) | 150–180 |
| Compressive strength (N/mm2) | 800–1000 |
| Tensile strength (N/mm2) | 35–40 |
| Vickers hardness (HV) | 400–650 |
| Electrical resistivity (Ω·cm) | (50–90)×10−6 |