Rare earth magnets: neodymium vs samarium-cobalt
By RareMetals.net Editorial Team · Published
Rare earth magnets are permanent magnets made from alloys of rare earth elements. There are two kinds: neodymium-iron-boron (NdFeB) magnets, the strongest permanent magnets made, and samarium-cobalt (SmCo) magnets, which are slightly weaker but keep their strength at much higher temperatures. Magnets are the largest use of rare earths worldwide (USGS), and they are why neodymium, praseodymium, dysprosium and terbium matter so much to electric vehicles, wind power and defence.
Neodymium vs samarium-cobalt magnets
| Neodymium (NdFeB) | Samarium-cobalt (SmCo) | |
|---|---|---|
| Main rare earths | Neodymium and praseodymium; dysprosium or terbium in high-temperature grades | Samarium (with cobalt, plus iron, copper and zirconium in Sm₂Co₁₇) |
| Strength at room temperature | Highest of any permanent magnet: maximum energy product up to about 55 MGOe (grade N55) | Lower: about 16-32 MGOe |
| Maximum working temperature | About 80 °C for standard grades; up to about 200-230 °C for grades with dysprosium or terbium | About 250-350 °C |
| Corrosion | Rusts easily; needs nickel, zinc or epoxy coating | Good resistance; usually uncoated |
| Main uses | EV motors, wind turbines, industrial motors, electronics, speakers | Aerospace and defence actuators, missile guidance, high-temperature motors and sensors |
| Invented | Early 1980s (Sumitomo Special Metals and General Motors) | 1960s-1970s |
What are neodymium magnets made of?
A sintered NdFeB magnet is roughly 65-70% iron, about 30% rare earths (mostly neodymium, with some praseodymium) and about 1% boron, in the crystal Nd₂Fe₁₄B. Grades that must work hot add a few percent of dysprosium or terbium, increasingly by grain-boundary diffusion, which places the heavy rare earth only at the grain edges and cuts the amount needed. The finished magnet is plated because the alloy corrodes quickly.
Most magnets are sintered: alloy powder is pressed in a magnetic field, heated until it fuses, machined and magnetised. Bonded magnets mix NdFeB powder with plastic; they are weaker but can be moulded into complex shapes for small motors and sensors.
Neodymium magnet grades explained
The number in a grade such as N42 or N52 is the maximum energy product in megagauss-oersteds (MGOe): the higher the number, the stronger the magnet for its size. A letter suffix gives the temperature rating.
| Suffix | Approximate maximum working temperature |
|---|---|
| None (N) | 80 °C |
| M | 100 °C |
| H | 120 °C |
| SH | 150 °C |
| UH | 180 °C |
| EH | 200 °C |
| AH | 220-230 °C |
Higher temperature grades need more dysprosium or terbium, which is why EV traction-motor magnets (usually SH to EH) use heavy rare earths while magnets in phones and speakers do not.
What are rare earth magnets used for?
- Electric vehicles. Most EV traction motors are permanent-magnet motors, typically with one to two kilograms of NdFeB. Power steering, pumps, seats and window motors add more in every modern car.
- Wind turbines. Direct-drive and medium-speed turbines, common offshore, use several hundred kilograms of NdFeB per megawatt.
- Industrial motors and robots. Permanent-magnet motors are smaller and more efficient than induction motors.
- Electronics. Hard-drive actuators, phone speakers and vibration motors, headphones, cameras.
- Defence and aerospace. Guidance and control actuators, radar, satellites and drones; SmCo dominates where temperatures are high.
- Medical and other. Some MRI machines, magnetic separators, sensors and couplings.
Where rare earth magnets are made
China makes about 90% of the world’s NdFeB magnets and separates most of the neodymium, praseodymium, dysprosium and terbium they need. It has banned the export of magnet-making technology since December 2023 and has required export licences for dysprosium, terbium and samarium since April 2025 (see China’s rare earth export controls).
Outside China, sintered magnets are made in Japan (Shin-Etsu, Proterial, TDK), Germany (Vacuumschmelze) and, increasingly, in Estonia (Neo Performance Materials’ Narva plant, opened 2025) and the United States (MP Materials in Fort Worth, Texas; USA Rare Earth in Stillwater, Oklahoma; Vacuumschmelze’s South Carolina plant). US samarium-cobalt makers include Arnold Magnetic Technologies and Electron Energy Corporation. In July 2025 the US Department of Defense agreed to buy magnets from MP Materials’ planned second US plant and set a price floor for its NdPr oxide.
For the raw-material side, see the neodymium and dysprosium pages and current neodymium and dysprosium prices.
Handling neodymium magnets safely
- Large magnets snap together with enough force to pinch skin or break fingers; handle them one at a time.
- Magnets are brittle and can chip or shatter when they collide; wear eye protection with strong magnets.
- Swallowed magnets can attract each other through the intestine walls and cause serious injury; keep small magnets away from children.
- Keep strong magnets away from pacemakers, implanted devices, credit cards and hard drives.
- Heat above the grade’s rated temperature permanently weakens the magnet. NdFeB dust can ignite, so do not grind magnets.
Rare earth magnet FAQ
Are neodymium magnets the same as rare earth magnets?
Neodymium magnets are one type of rare earth magnet, and by far the most common. The other type is samarium-cobalt.
Which is stronger, N52 or N42?
N52. The number is the maximum energy product in MGOe, so an N52 magnet stores about 24% more magnetic energy than an N42 magnet of the same size. N52 is usually the strongest grade sold in quantity.
Do neodymium magnets lose their magnetism?
Very slowly at room temperature, if they are not overheated, corroded or exposed to strong opposing fields. Heating above the rated temperature or physical damage causes permanent loss.
Why are samarium-cobalt magnets used in missiles and aircraft?
They keep their strength up to about 350 °C and resist corrosion without coatings, which neodymium magnets cannot do.
Can rare earth magnets be recycled?
Yes, but little is recycled today. Most recycling uses factory scrap; recovering magnets from hard drives, motors and turbines is growing with new plants in the US, Europe and Japan.
Sources: USGS Mineral Commodity Summaries 2026; manufacturer data sheets for grade temperatures. General information only.