Key Takeaways
- ◆NdFeB delivers 30–50% higher energy density than SmCo at equivalent temperature ratings up to ~180°C.
- ◆SmCo 2:17 operates to 300–350°C continuous — well beyond any commercial NdFeB grade.
- ◆SmCo has ~4x lower temperature coefficient of Br (~-0.03%/°C vs NdFeB's -0.12%/°C), so SmCo is more thermally stable even where NdFeB technically works.
- ◆NdFeB requires coating to prevent corrosion; SmCo is essentially immune to atmospheric corrosion and used uncoated in most environments.
- ◆NdFeB is 30–60% cheaper per MGOe at 2026 pricing. SmCo cost pressure comes from cobalt (strategic material), not rare earths.
- ◆Both are subject to China MOFCOM export licensing — switching materials does not avoid licensing requirements.
Overview
NdFeB (neodymium-iron-boron) and SmCo (samarium-cobalt) are the two commercial rare earth magnet materials. NdFeB dominates by volume (roughly 90:1 ratio in global production) because of its higher energy density and lower cost. SmCo retains a niche where its temperature stability and corrosion resistance are decisive design factors. Both materials require thoughtful grade selection, and for designs in the 150–200°C envelope, both should be evaluated in parallel.
Side-by-Side Comparison
| Criterion | NdFeB (Neodymium) | SmCo (Samarium-Cobalt) |
|---|---|---|
| Max BHmax (premium grades) | ✓Up to 53 MGOe (N52) | Up to 32 MGOe (SmCo 2:17) |
| Max Operating Temperature | 200°C (EH grades) | ✓300–350°C (SmCo 2:17) |
| Temperature Coefficient Br | -0.12%/°C | ✓-0.03%/°C |
| Corrosion Resistance (uncoated) | Poor | ✓Excellent |
| Cost per MGOe | ✓Lower (baseline) | 2–4x NdFeB |
| Mechanical Strength (flexural) | ✓~250 MPa | ~120 MPa |
| Heavy Rare Earth Dependence | Dy/Tb for high temp | Samarium (controlled) |
| Global Production Volume | ✓~220,000 t/yr | ~2,500 t/yr |
Green tick indicates the better option for the criterion. Winner assignment reflects typical engineering practice; your application may weight criteria differently.
When NdFeB (Neodymium) Is the Right Choice
- •Operating temperature at or below 180°C continuously
- •Cost-sensitive production applications
- •Designs requiring maximum flux density in minimum volume
- •Applications where mechanical robustness matters (NdFeB is less brittle)
When SmCo (Samarium-Cobalt) Is the Right Choice
- •Operating temperature continuously above 200°C (aerospace, downhole, defense)
- •Applications with wide temperature swings where thermal stability of flux is critical
- •Vacuum and spacecraft applications requiring zero outgassing
- •Designs where coating pinhole integrity is a reliability concern
Decision Framework
Start with operating temperature. Above 200°C continuous, SmCo 2:17 wins by default — NdFeB simply does not operate there. Between 150–200°C, evaluate both: NdFeB UH and EH grades offer competitive total-cost positions with the GBD processing premium, while SmCo offers inherent thermal stability without compensation design. Below 150°C, NdFeB is almost always the correct material — cheaper, higher BHmax, easier to procure at volume.
Frequently Asked Questions
Which is stronger, NdFeB or SmCo?
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NdFeB is stronger in terms of energy density — the most powerful commercial NdFeB (N52) delivers up to 53 MGOe, versus up to 32 MGOe for the strongest SmCo (SmCo 2:17). In practical motor design, NdFeB allows smaller, lighter motors at the same torque output. However, SmCo wins at elevated temperatures where NdFeB flux would demagnetize.
Why is SmCo used instead of NdFeB?
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SmCo is chosen when its specific advantages outweigh NdFeB's higher energy density. These scenarios include: continuous operation above 200°C, applications with wide temperature swings where thermal stability of flux matters, vacuum and spacecraft use (SmCo has near-zero outgassing), and environments where coating pinhole reliability is a concern (SmCo is essentially immune to atmospheric corrosion uncoated).
Is SmCo cheaper than NdFeB?
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No, SmCo is typically 2–4x more expensive than NdFeB per MGOe of energy product at 2026 pricing. The cost pressure on SmCo comes primarily from cobalt content — cobalt is a strategic material with volatile pricing tied to battery supply chains. NdFeB cost pressure tracks rare earth markets (NdPr, Dy, Tb) and is usually lower per unit of magnetic work delivered.
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