NdFeB vs SmCo Magnets: Which Rare Earth Material to Choose for Your Motor, Actuator, or Sensor

Sintered NdFeB (neodymium-iron-boron) and sintered SmCo (samarium-cobalt) are the two commercially dominant rare earth permanent magnet materials. NdFeB was developed commercially by General Motors and Sumitomo in 1984 and rapidly displaced SmCo in most applications due to higher energy density and lower cost. SmCo, developed in the 1960s, retained a niche where its superior temperature stability and corrosion resistance outweigh NdFeB's energy-density advantage. In 2026, global NdFeB production runs approximately 220,000 tonnes per year; SmCo production is roughly 2,500 tonnes per year. The volume ratio — roughly 90:1 — tells you NdFeB wins the commercial center of gravity. The specification ratio tells a different story: SmCo delivers in thermal envelopes where NdFeB simply cannot survive.

Maximum energy product (BHmax) is the single most important metric differentiating permanent magnet materials. NdFeB's commercial range is 33–53 MGOe across standard through premium grades. SmCo 1:5 delivers 16–22 MGOe; SmCo 2:17 delivers 22–32 MGOe. In other words, premium NdFeB (N48SH, N52) delivers roughly double the energy density of premium SmCo 2:17. For any application where operating temperature stays at or below 180°C and flux density drives design, NdFeB is the correct choice. A motor designed for N48SH and switched to SmCo 2:17 would require approximately 40–60% more magnet volume to achieve equivalent flux — that is an unworkable compromise in packaging-constrained designs.

• •Premium NdFeB (N52): up to 53 MGOe — highest commercial energy density
• •Premium SmCo (2:17): up to 32 MGOe — approximately 60% of N52
• •Standard SmCo (1:5): up to 22 MGOe — adequate for moderate flux needs
• •Volume required for equivalent flux: SmCo typically 40–60% more than NdFeB

Temperature stability is where SmCo reverses the advantage. NdFeB's maximum continuous operating temperature peaks at 200°C (EH grades), and even that requires substantial Dy/Tb content and careful design. SmCo 1:5 is rated to 250°C continuous; SmCo 2:17 is rated to 300–350°C continuous. Beyond max temperature, SmCo's temperature coefficient of remanence (Br) is approximately −0.03%/°C, versus NdFeB's ~−0.12%/°C. In practical terms: if you need magnet performance to be consistent across a wide temperature range, SmCo derates about one-quarter as much as NdFeB per degree. This matters for precision instruments, aerospace applications with wide ambient swings, and any design where thermal compensation of magnet output is otherwise required.

NdFeB is chemically reactive and corrodes rapidly in humid air without coating — oxidation initiates at grain boundaries and propagates inward. Coating is non-negotiable for practical NdFeB use, with NiCuNi (24–72 hour salt spray) and epoxy-over-NiCuNi (96–200+ hour salt spray) as typical options. SmCo is essentially immune to atmospheric corrosion and can be used uncoated in most environments. This simplifies design for vacuum, aerospace, and biomedical implants where coating pinhole integrity is critical. Mechanically, both materials are brittle and crack under tensile or shear loads — neither should be used as a structural element, and adhesive bonding or mechanical retention is always required.

• •NdFeB: coating required (NiCuNi, epoxy, parylene); without coating, corrodes within weeks in humid air
• •SmCo: essentially immune to atmospheric corrosion; uncoated use is routine
• •NdFeB: Vickers hardness 550–650 HV; brittle; typical flexural strength ~250 MPa
• •SmCo: Vickers hardness 450–550 HV; brittle; typical flexural strength ~120 MPa (more fragile than NdFeB)

On a dollar-per-MGOe basis, NdFeB is substantially cheaper than SmCo at 2026 pricing. A rough 2026 rule: NdFeB finished-magnet pricing runs USD 60–120 per kilogram depending on grade and GBD content; SmCo runs USD 140–280 per kilogram. SmCo's cost pressure is driven by cobalt, not samarium — cobalt is a strategic material with volatile pricing tied to battery supply chains. This means NdFeB pricing tracks rare earth markets (NdPr, Dy, Tb), while SmCo pricing tracks cobalt markets. For cost-sensitive high-volume applications, NdFeB is almost always the answer; for niche high-temperature applications, the cost premium of SmCo is often justified by the performance it delivers.

Apply these questions in order to converge on the correct material for your application:

• •Is operating temperature above 200°C continuously? — Use SmCo 2:17
• •Is operating temperature 180–200°C? — Evaluate both; SmCo 2:17 often wins on stability, NdFeB EH on BHmax. Check your derating curves
• •Is operating temperature 150–180°C? — Use NdFeB UH grades (GBD-processed) unless you need SmCo for other reasons (corrosion, low tempco)
• •Is operating temperature below 150°C? — Use NdFeB; grade selected by BHmax requirement and cost target
• •Is corrosion resistance without coating critical? — Consider SmCo even at lower temperatures
• •Is flux stability across wide temperature swings critical? — SmCo's lower tempco may justify the cost
• •Is cost the dominant constraint? — NdFeB, every time, unless the temperature envelope rules it out

Both NdFeB (with heavy rare earth content) and SmCo fall under China's April 2025 MOFCOM export controls. Any high-temperature NdFeB (H, SH, UH, EH grades) containing Dy or Tb requires licensing; SmCo in all forms is also on the controlled list due to samarium's inclusion. In practice, licensing timelines and approval patterns are similar for both materials. A supplier that handles MOFCOM licensing in-house for NdFeB will typically handle SmCo on the same infrastructure. Neither material offers a licensing-free alternative for buyers seeking to avoid the Chinese export regime entirely.

Our core specialization is sintered NdFeB across the full grade spectrum including GBD processing, but we also supply sintered SmCo 1:5 and SmCo 2:17 for applications where SmCo is the correct material. For customers working through material selection, we provide side-by-side specification analysis including at-temperature BH curves, corrosion testing data, and total-landed-cost comparison. Our engineering team routinely recommends SmCo over NdFeB when the application envelope supports that choice — the right material is the one that fits the design, not the one with higher margin.