Neodymium, ferrite or samarium cobalt: what is the difference?
Short answer: neodymium (NdFeB) is the strongest permanent magnet: about 10 times as strong as ferrite of the same size. It works up to approx. 80 °C and needs a coating against corrosion. Ferrite (ceramic magnet) is weaker, but cheap, rust-free and resistant up to approx. 250 °C. Samarium cobalt (SmCo) is slightly weaker than neodymium, does not rust and withstands 250 – 350 °C, but is expensive. Choose neodymium when you need a lot of force in little space.
Comparison in one table
| Neodymium (NdFeB) | Samarium cobalt (SmCo) | AlNiCo | Ferrite | Flexible magnet | |
|---|---|---|---|---|---|
| Energy product BHmax | 33 – 53 MGOe | 16 – 32 MGOe | 1.5 – 10 MGOe | 1 – 4.5 MGOe | 0.6 – 1.5 MGOe |
| Relative strength (same size) | very high | high | low to medium | low | very low |
| Max. temperature | 80 °C (special grades up to 200+ °C) | 250 – 350 °C | 450 – 550 °C | approx. 250 °C | approx. 70 °C |
| Corrosion | yes, coating required | no | no | no | no |
| Resistance to demagnetisation | high | very high | low | medium | medium |
| Brittleness | brittle | very brittle | tough | brittle | flexible |
| Price per kg of holding power | low to medium | high | high | very low | low |
| Typical use | closures, fixing, motors, earbuds | aerospace, sensors at high temperature | guitar pickups, measuring instruments | fridge magnets, loudspeakers, motors | magnetic sheet, advertising |
When do you choose which magnet?
- Neodymium: when you want a lot of force in a small magnet. Almost all fixing, closing and hanging applications. See our neodymium magnets.
- Neodymium with a high-temperature grade (H, SH): for heat up to 120 – 150 °C, such as in motors. See magnets at high temperatures.
- Samarium cobalt: at 150 – 350 °C or in corrosive environments where a coating is not an option.
- Ferrite: when space and weight do not matter and price counts, or outdoors without a coating.
- Flexible magnet: for large, flexible surfaces such as vehicle signs or whiteboard letters.
How much stronger is neodymium than ferrite?
At the same size, neodymium has about 10 times the energy product (for example 42 versus 4 MGOe). In practice this means a neodymium disc of Ø10 x 3 mm (approx. 1.6 kg) holds about as much as a ferrite magnet the size of a large coin. That is why neodymium allows invisible closures and compact products. See how strong is a neodymium magnet?
How do you recognise a neodymium magnet?
- Neodymium: usually shiny silver (nickel), sometimes black (epoxy) or gold; heavy (7.5 g/cm³) and surprisingly strong for its size.
- Ferrite: matt dark grey to black, light (approx. 5 g/cm³), feels like ceramic; leaves grey powder when scratched.
- AlNiCo: often a cast horseshoe or bar, painted red in schools.
Frequently asked questions
Are there magnets stronger than neodymium?
Not as a permanent magnet at room temperature. Electromagnets and superconducting magnets can create stronger fields, but need power (and cooling).
Is neodymium more expensive than ferrite?
Per piece yes, per kilo of holding power often not, because you need a much smaller magnet.
Why do loudspeakers often contain ferrite magnets?
Because they are cheap and a large loudspeaker has enough space. Earbuds and small speakers use neodymium.
Read also
Need help choosing? Use the Magnet Advisor or contact us.
