Samarium-cobalt (SmCo) magnets are the rare-earth magnets built for the toughest jobs. They are made from samarium, a rare-earth metal, and cobalt, plus small amounts of copper, iron and zirconium. Their special talent is simple: they keep working where other magnets give up.
What makes SmCo special
Heat is the enemy of most magnets, but not SmCo. Good grades work continuously at 250 °C, and the strongest Sm2Co17 grades handle up to 350 °C — far beyond what NdFeB can survive. Its field also stays remarkably steady as temperatures change, which matters for precision sensors. SmCo even shrugs off corrosion: because it contains very little iron, it barely rusts, so it usually needs no coating at all.
The trade-off
SmCo is not the strongest magnet — NdFeB beats it at room temperature. And it is expensive: samarium is scarce, and cobalt is a costly strategic metal. You pay for heat tolerance and reliability, not raw power. For everyday jobs like fridge magnets, toys or speakers, that price is hard to justify — SmCo earns its keep only where the environment turns hostile.
Where SmCo is used
- Aerospace and defense — actuators, generators and sensors that must never fail at altitude.
- Automotive sensors — ABS and position sensors that sit near hot engines.
- High-temperature motors — in aircraft and industrial drives.
- Sealed pumps and couplings — where uncoated magnets handle corrosive fluids.
If your application runs hot, corrosive or both, SmCo is usually the answer. If not, NdFeB or ferrite will do the job for less.
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