SmCo vs NdFeB: Which Rare Earth Magnet Is Right for Your Application?

Samarium cobalt (SmCo) and neodymium iron boron (NdFeB) are the two families of rare earth permanent magnets.

They are both sintered alloys with exceptional magnetic properties relative to their size, however they are not interchangeable.

Selecting the wrong one for your application will result in either unnecessary cost (SmCo where NdFeB would perform) or premature field loss, coating failure, or assembly failure (NdFeB where SmCo was the correct answer).

This guide gives you everything you need to make the right choice when choosing between the two.

Quick answer

Use NdFeB when you need the strongest magnetic performance at room temperature and compact size.

Use SmCo when the application involves high temperature, corrosion risk, strong demagnetising fields, or field stability over a wide temperature range.

The fundamental trade-off

NdFeB is the stronger magnet at room temperature. SmCo is the more stable magnet at elevated temperature, in corrosive environments, and wherever field consistency over a wide temperature range is a design requirement.

The two materials do not simply occupy different price points – they have genuinely different performance profiles, and the right choice depends on what your application actually demands.

NdFeB dominates at ambient temperature. The strongest NdFeB grade (N52) produces a BHmax of approximately 52 MGOe — more than 60% greater than the best SmCo grade (SmCo32 at 32 MGOe). In any application where space is constrained and operating temperature is below 80–120°C, NdFeB produces more field from a smaller volume of material at lower cost. This is why NdFeB is the default choice for consumer electronics, general industrial holding, and most ambient-temperature applications.

SmCo takes over above 150–180°C. NdFeB’s temperature coefficient — the rate at which field strength drops as temperature rises — is approximately −0.09 to −0.13%/°C. SmCo 2:17’s temperature coefficient is −0.03%/°C. This difference compounds: by 200°C, an NdFeB-EH grade is approaching its design limit and operating with a significantly reduced field; SmCo 2:17 has retained over 94% of its room-temperature performance and is nowhere near its ceiling. Above 200°C, SmCo has no NdFeB competitor. Above 250°C, only SmCo is viable. At 350°C, SmCo 2:17 H series is the only rare earth magnet option.

Corrosion resistance is an important differentiator. NdFeB has a high iron content and will corrode rapidly without a coating in humid or wet environments. Proper coating selection (epoxy, PTFE, NiCuNi + epoxy) addresses this for most applications, but adds cost, dimensions, and complexity. SmCo 1:5 contains no iron and is inherently corrosion-resistant – used uncoated in most environments. In applications where coating reliability is a concern (food processing, offshore, downhole, medical), SmCo’s inherent corrosion resistance removes a significant point of failure.

Property comparison: NdFeB vs SmCo

The table below compares the two material families across the properties most relevant to industrial specification decisions. Highlighted cells indicate the clear advantage for that property. Where both materials have comparable performance or competing risks, this is noted.

Samarium cobalt vs neodymium: temperature ranges

Application-by-application material recommendation

The table below provides recommended material for common industrial and commercial applications, with the specific grade and rationale for each recommendation. These are starting points — always validate against your specific operating temperature, environment, and performance requirements.

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