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Is Cobalt Magnetic?
So, is cobalt magnetic? Yes. Cobalt is one of only three metals that are ferromagnetic at room temperature, the others being iron and nickel. That means pure cobalt is strongly attracted to a magnet and can be magnetised itself, unlike paramagnetic or diamagnetic metals, which react only weakly.
Cobalt can be recognised as a silvery-blue transition metal. It’s best known today as an ingredient in the cathodes of many lithium-ion batteries, but it has been important in the magnet industry for nearly a century.
Why Is Cobalt Magnetic?
Let’s get into the science. A metal’s magnetism comes from its atomic structure. Cobalt has unpaired electrons in its 3d subshell, so each cobalt atom acts as a tiny magnetic dipole.
In ferromagnetic metals these atomic dipoles line up with their neighbours in regions called magnetic domains. When most of the domains in a piece of cobalt point the same way, the whole piece behaves as a magnet.
Cobalt’s Curie Temperature
Cobalt is also quite special in its material properties, with the highest Curie temperature of any element: about 1,115 °C. The Curie temperature is the point where a material loses its ferromagnetism, so cobalt keeps its magnetic order at far higher temperatures than iron (about 770 °C) or nickel (about 358 °C).
This makes it an ideal material for high-temperature environments such as motors.
Is Cobalt Used in Magnets?
Yes, and that high-temperature stability is the main reason. Pure cobalt doesn’t hold its magnetism strongly on its own, so it’s almost always used in alloys designed for a job:
- Samarium cobalt (SmCo): very strong permanent magnets that keep working at high temperatures (typically up to 250–350 °C) and resist corrosion well. They’re used in high-performance motors, generators, aerospace and sensors.
- Alnico (aluminium, nickel and cobalt): cast or sintered magnets with excellent temperature stability, used in sensors, guitar pickups, meters and pot magnets.
Cobalt in Other Magnetic Materials
- Neodymium magnets: many grades contain a small amount of cobalt to improve heat and corrosion resistance.
- Soft magnetic alloys: iron-cobalt alloys (for example Hiperco) are widely used in motors, transformers and aerospace equipment because they carry very high magnetic flux.
Hard and Soft Cobalt Magnets
Cobalt alloys can be made into both kinds of magnetic material.
- Hard (permanent) magnets, such as SmCo and Alnico, need a lot of energy to magnetise, but once magnetised they stay magnetised.
- Soft magnetic materials, such as iron-cobalt, magnetise and demagnetise easily. They don’t stay magnetised, which is exactly what you want in a transformer or motor core.
Can Cobalt Be Magnetised, and How?
Yes. To magnetise cobalt or a cobalt alloy, you place it in a strong external magnetic field, usually inside a coil or a pulse magnetiser, so its domains line up in one direction.
- Pure cobalt is fairly “soft”: it’s attracted to magnets and can be magnetised, but it doesn’t hold much magnetism once the field is removed.
- SmCo and Alnico magnets are magnetised after they’ve been made and shaped, and they then hold their magnetism for many years.
- Heating cobalt past its Curie point (about 1,115 °C) removes its magnetism. It can only be magnetised again once it has cooled.
Conclusion
In short: cobalt is magnetic, it holds that magnetism at higher temperatures than any other element, and that’s why it’s a key ingredient in samarium cobalt and Alnico magnets for demanding, high-temperature applications.
Browse our samarium cobalt magnet grades and alnico magnets, or use our free magnet pull-force calculator.
See how this compares with other metals in our guide to which metals are magnetic.
FAQs
Do magnets stick to cobalt?
Yes. Cobalt is ferromagnetic, so a magnet is strongly attracted to pure cobalt, just as it is to iron and nickel.
Is cobalt magnetic at high temperatures?
Yes. Cobalt has the highest Curie temperature of any element, about 1,115 °C, so it keeps its magnetic order far longer than iron or nickel as it heats up.
What magnets contain cobalt?
Samarium cobalt (SmCo) and Alnico magnets are based on cobalt, and many neodymium grades contain a small amount of cobalt to improve heat and corrosion resistance.
Can pure cobalt be a permanent magnet?
Pure cobalt can be magnetised, but it doesn’t hold much magnetism once the field is removed. Permanent cobalt magnets are made from alloys such as SmCo and Alnico.
What stops cobalt being magnetic?
Heating it past its Curie point, about 1,115 °C, removes its magnetism. Strong opposing magnetic fields can also demagnetise cobalt alloys.
Is samarium cobalt better than neodymium?
It depends on the job. Neodymium magnets are stronger at room temperature, while samarium cobalt magnets cope better with high temperatures and corrosion.