The NdFeB vs SmCo question reaches our quoting desk in a familiar form: the same part, priced in both materials, because the customer’s thermal environment sits in the grey zone where either could work. And almost every one of those conversations starts from the same three misconceptions — that SmCo is “just a more expensive NdFeB”, that NdFeB cannot survive anywhere near a furnace, and that switching to SmCo is a way around China’s export-licensing paperwork.
None of the three survives contact with the data. The honest NdFeB vs SmCo comparison comes down to three factors: how the temperature curve behaves, what the total cost really is once you include coatings and scrap, and what the export-control list actually says about each material. This article puts numbers on all three. If you want the per-grade detail behind the NdFeB side first, our neodymium magnet grades chart covers it.
NdFeB vs SmCo at a Glance
| Property | Sintered NdFeB | Sintered SmCo |
|---|---|---|
| Max energy product (BH)max | 30–55 MGOe | 16–32 MGOe (2:17); 14–24 MGOe (1:5) |
| Remanence Br | 1.0–1.45 T | 0.85–1.15 T |
| Max operating temperature | 80–230 °C (grade-dependent) | 250–350 °C |
| Curie temperature | 310–370 °C | 700–850 °C |
| Temperature coefficient of Br | −0.09 to −0.13 %/°C | −0.03 to −0.05 %/°C |
| Temperature coefficient of HcJ | −0.40 to −0.60 %/°C | −0.20 to −0.30 %/°C |
| Corrosion resistance | Poor — coating mandatory | Excellent — often used bare |
| Density | 7.4–7.7 g/cm³ | 8.2–8.5 g/cm³ |
| Typical relative cost (per kg) | 1× baseline | Roughly 5–10× |
| Two families | N to AH, one chemistry | SmCo₅ (1:5) and Sm₂Co₁₇ (2:17) |
Two families on the SmCo side deserve a word: SmCo₅ (1:5) tops out around 250 °C with the higher coercivity, and Sm₂Co₁₇ (2:17) reaches 300–350 °C with more flux density. If a vendor quotes you “SmCo” without saying which, that is the first question to ask.
Temperature: Where the Two Curves Actually Diverge
The headline difference is not the maximum temperature — it is the slope. Remanence falls as temperature rises in both materials, but NdFeB loses it roughly three times faster than SmCo.
Run the arithmetic. Take a typical NdFeB grade with a Br coefficient of −0.11 %/°C, moved from 20 °C to 200 °C: that is 180 °C × 0.11 % ≈ a 20 % drop in remanence — reversible, provided the grade has the coercivity to survive, but 20 % is a design input you must have planned for. A SmCo 2:17 with a −0.035 %/°C coefficient moved from 20 °C to 300 °C loses about 280 °C × 0.035 % ≈ 10 % — at a temperature 100 °C higher.
Three consequences follow, and they are the real content of the “which one” decision:
Above roughly 200 °C, the comparison inverts. NdFeB’s top grades (EH, AH) reach 200–230 °C only by adding heavy rare earths, and at those grades the price gap with SmCo narrows sharply — while SmCo still holds a 100+ °C margin to its Curie point. In our experience, once a specification passes 200 °C continuous, SmCo usually wins on engineering merit before cost is even discussed.
Between 150 °C and 200 °C is the true grey zone where the same part can be built either way. This is where the cost math of the next section matters most — high-coercivity NdFeB (SH/UH) versus SmCo 1:5.
The coefficient is a stability spec, not just a survival spec. Precision sensors, torque instruments and anything with a calibrated magnetic circuit care how much the field moves with temperature, not just whether the magnet survives. For those, SmCo’s flatter curve is a performance feature that no NdFeB grade can match.
If your question is specifically thermal, our high-temperature NdFeB selection guide walks the grade-by-grade logic on the NdFeB side.
Strength and Size: What the Energy Product Gap Means
NdFeB stores roughly 1.5 to 2 times the magnetic energy per unit volume (55 vs 32 MGOe at the top of each range). For the same flux in the same gap, a SmCo part needs more volume — and, being denser (8.2–8.5 vs 7.4–7.7 g/cm³), more mass on top of that.
In practice this matters in two opposite directions:
- Volume-constrained designs (compact motors, actuators, anything where millimetres are priced) favour NdFeB heavily. Below 150 °C this advantage is nearly always decisive.
- Mass-critical but thermally brutal designs — aerospace and downhole, say — accept the extra SmCo volume because the alternative is a NdFeB grade carrying heavy rare earths at a converging price, with a thinner thermal margin.
Corrosion and Coating: The Hidden Cost Line
NdFeB is an iron-rich material and oxidises readily; a coating is not an option but a specification. NiCuNi plating is the industrial default, zinc is the budget route, epoxy and Parylene serve wet, saline or medical environments. Coatings add cost, add tolerance layers, and introduce a failure mode of their own — a scratched or degraded coating on a NdFeB magnet in a humid environment is a time bomb.
SmCo contains no free iron and is naturally oxidation-resistant; in most environments it is used bare. For marine, subsea, chemical-processing and long-lifetime applications, that difference is structural: there is no coating to specify, tolerance to lose, or degradation to monitor over a 20-year service life.
When you compare quotations, make sure the NdFeB price includes its coating and the process scrap behind it — which brings us to cost proper.
Cost: Per Kilogram Is the Wrong Metric
On a per-kilogram basis, SmCo typically runs roughly 5–10× the price of equivalent NdFeB — the multiple moves with cobalt prices and with grade. Quoted like that, the comparison looks like a rout. It is not, for three reasons.
First, the metric that matters is cost per unit of magnetic energy in the working gap — and NdFeB’s energy-product advantage claws back part of the per-kilogram gap, because less NdFeB material is needed for the same flux.
Second, the gap narrows with temperature. High-coercivity NdFeB grades buy their temperature rating with dysprosium and terbium, which are expensive. By the time a specification demands EH or AH class NdFeB (200–230 °C), the material-cost gap against SmCo has contracted enough that the two are routinely quoted within striking distance — and SmCo still holds the larger thermal reserve.
Third, SmCo deletes cost lines that NdFeB adds: no plating line, no coating tolerance allowance, no coating-failure warranty exposure, and (being less magnetic-sensitive in machining) no demagnetisation losses in process. In corrosive or long-lifetime applications, the bare SmCo part is frequently the cheaper installed-and-forgotten option even at a higher sticker price.
One machining note that belongs in any cost model: SmCo is more brittle than NdFeB — it chips at edges more readily and is typically ground with diamond tooling. Thin sections and sharp corners cost more in SmCo, and transit packaging needs more care. Quote both materials with realistic geometry before deciding.
Supply Risk: The Factor Most Comparisons Miss
This is the section that most NdFeB-vs-SmCo articles get wrong, because they were written before April 2025. The question buyers now ask us is some version of: “if NdFeB needs export licences now, should we switch to SmCo to avoid the paperwork?”
No — and the official text says so directly. Announcement No. 18 of April 2025 (the MOFCOM/GACC export-control regime our compliance series covers) lists, among samarium-related items, “samarium cobalt permanent magnet materials” as a controlled item in its own right — control code 1C902.a.4, covering magnets and magnet powder. On the NdFeB side, the list captures NdFeB permanent-magnet materials containing terbium (1C904.a.4) or dysprosium (1C905.a.4).
Put side by side:
| Material | Position under Announcement No. 18 | Licence needed? |
|---|---|---|
| NdFeB without Dy/Tb (typically N through SH) | Not on the control list | No |
| NdFeB containing Dy/Tb (typically UH, EH, AH) | Listed: 1C904.a.4 / 1C905.a.4 | Yes |
| SmCo — any grade | Listed: 1C902.a.4 (the material family itself) | Yes |
The comparison, then, is not “controlled versus uncontrolled”. It is “uncontrolled versus controlled” on one axis, and on the other axis the two families simply route through the same licensing system. If a part falls under 1C902.a.4, the licence review is the same machinery as for a controlled NdFeB part — and the planning consequences in our export-licence timeline apply in the same way. For how classification is decided from composition, see does your magnet need an export licence?; the underlying regime is explained in our Announcement No. 18 guide.
Two further supply-risk differences are worth weighing:
Production scale is wildly asymmetric. Sintered NdFeB is a mass industry — global output is on the order of hundreds of thousands of tonnes a year, with the large majority produced in China — while SmCo output is one-to-two orders of magnitude smaller, a specialised few thousand tonnes. Consequences: wider grade availability, shorter standard lead times and more second-source options on the NdFeB side; longer lead times, smaller batches and more make-to-order on the SmCo side.
The raw-material risk has a different shape. NdFeB pricing rides on neodymium-praseodymium and, in high-temperature grades, on Dy/Tb; SmCo pricing rides on samarium and above all cobalt, a metal with its own volatility and its own geopolitical story. Neither is risk-free; they are different risks, and a dual-material qualification is often the honest hedge.
There is one genuinely clean route around heavy rare earths, and it is not SmCo: it is our HRE-free NdFeB — grain-boundary-diffusion grades that reach SH-class coercivity without dysprosium or terbium, keeping the part off the control list while holding the temperature rating. The engineering detail is in our HRE-free guide.
The Decision Framework
| Your situation | Choose | Why |
|---|---|---|
| Below 150 °C, benign environment, cost- or volume-sensitive | NdFeB | Higher energy product, mass-market supply, no contest on value |
| 150–200 °C, precision field stability required | Compare seriously | High-coercivity NdFeB (SH/UH) vs SmCo 1:5 — cost and stability both close |
| Above 200 °C continuous | SmCo | 250–350 °C capability, flatter curve, converging cost |
| Marine / chemical / no-coating-allowed | SmCo | Bare use, no coating failure mode |
| Calibrated magnetic circuits, thermal cycling | SmCo | −0.035 %/°C vs −0.11 %/°C is a spec, not a nicety |
| Schedule-driven, needs an uncontrolled supply route | HRE-free NdFeB | Off the control list entirely — SmCo is on it |
| Thin, sharp, complex geometry in volume | NdFeB | SmCo brittleness raises scrap and tooling cost |
FAQ
Which is stronger, NdFeB or SmCo? At room temperature, NdFeB — up to 55 MGOe against SmCo’s 32, so around 1.5–2× the energy per volume. But “stronger” is temperature-relative: at 300 °C a SmCo magnet still delivers about 90 % of its room-temperature flux while a NdFeB part has already left its usable range. In hot applications, SmCo is effectively the stronger magnet.
Can a high-temperature NdFeB grade replace SmCo? Often, yes — up to roughly 200 °C, grades like N42SH or N38UH are the standard substitutes, at lower cost. Above that, the heavy rare earth content required climbs, the price converges with SmCo, and the flatter SmCo curve usually wins. Evaluate the coefficient, not just the maximum temperature.
Is SmCo exempt from China’s export licence? No. SmCo permanent-magnet materials are themselves a controlled item under Announcement No. 18 (code 1C902.a.4). Dy/Tb-free NdFeB is the family that sits outside the list. Both licensed routes use the same review system and similar timelines.
Why is SmCo so much more expensive? Samarium and especially cobalt raw materials, much smaller production volumes (thousands of tonnes a year against NdFeB’s hundreds of thousands), more brittle machining with higher scrap, and smaller, more make-to-order batches. Above 200 °C, part of that premium is clawed back by the heavy rare earth cost inside high-grade NdFeB.
Does SmCo really not need a coating? In most environments, correct — no free iron means no rust mechanism. For salt spray, chemical contact or abrasion we still discuss a thin protective layer, but it is an engineering choice rather than a structural necessity as it is for NdFeB.
Key Takeaways
- Below 150 °C, NdFeB wins on value almost every time — higher energy product, mass-market supply chain, lower total cost.
- Above 200 °C, SmCo wins on engineering — 350 °C capability, a three-times-flatter temperature curve, and a converging price against Dy/Tb-heavy NdFeB.
- The 150–200 °C band is a genuine grey zone — quote both, including coatings, machining and scrap.
- Switching to SmCo does not escape export licensing — SmCo magnet materials are listed under Announcement No. 18 (1C902.a.4). The licence-free route is Dy/Tb-free, HRE-free NdFeB.
If you send us the drawing, the working temperature and the environment, we will quote it both ways — it is the fastest way to see where your part sits on the temperature-cost map. Start at our SmCo magnets page or NdFeB magnets page, or contact us directly.
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