Permanent magnets are magnets that maintain their own magnetic force without an external magnetic field. Currently, there are three types of permanent magnets most widely used in industry: neodymium (Nd-Fe-B), samarium-cobalt (SmCo), and ferrite (Ferrite/Sr-Ba) . The magnetic properties, temperature stability, and price range of each magnet vary greatly, making it essential to select one that suits the application.
Comparison of the three major permanent magnets at a glance
| Item | Nd-Fe-B (Sintered) | SmCo (1:5 / 2:17) | Ferrite (Sr/Ba) |
|---|---|---|---|
| Residual magnetic flux density Br | Approx. 1.2 ~ 1.4 T | Approx. 0.85 ~ 1.10 T | Approx. 0.35 ~ 0.45 T |
| Maximum energy BHmax | approx. 35 ~ 52 MGOe | approx. 18 ~ 32 MGOe | approx. 3.5 ~ 4.5 MGOe |
| Maximum operating temperature | 80℃ (N) ~ 220℃ (UH/EH) | 250 ~ 350℃ | Approx. 250℃ |
| Curie temperature Tc | Approximately 310 ~ 340℃ | Approximately 750 ~ 825℃ | Approximately 450℃ |
| Corrosion resistance | Weak (plating required) | Excellent | Excellent |
| Price (unit magnetic energy) | Medium high | Highest | Lowest |
| Main application areas | EV motor, BLDC, MRI | Aviation, defense, high temperature | General home appliances, speakers |
Nd-Fe-B (Neodymium) — The strongest magnetic energy
is the strongest commercially available permanent magnet since it was developed by Japan's Sumitomo Special Metals in the 1980s. The maximum magnetic energy per unit volume is so overwhelming that motors with the same output can be made smaller and lighter. The disadvantage is that it has a low Curie temperature and is weak against oxidation, so surface plating (Ni, Zn, epoxy) is essential.
There are H / SH / UH / EH grades with heavy rare earths such as Dy (dysprosium) and Tb (terbium) added for high temperature applications, and can be used up to approximately 120 / 150 / 180 / 200℃ respectively.
SmCo (samarium-cobalt) — extreme temperatures and corrosive environments
There are two series,1:5(SmCo5) and 2:17(Sm2Co17), with 2:17 generally showing higher BHmax. The Curie temperature is about 750~825℃, which is more than twice that of Nd, so its magnetism is stable even in high temperature environments of 250~350℃. Applications include aerospace and military actuators, high-temperature industrial pumps, and downhole (oil drilling) equipment.
Co price volatility is high and Sm is also a rare earth, so the unit price is the most expensive.
Ferrite — Price and corrosion resistance
is an oxide ceramic magnet based on iron oxide (Fe2O3). Its magnetic energy is low, about 1/10th of that of Nd, but it is extremely inexpensive and extremely resistant to corrosion and chemicals. It is most widely used in automobile wipers and window lifts, general home appliance motors, speaker magnets, and magnetic chucks.
Selection Guide — Recommended
by Application- EV Traction Motor, Industrial BLDC → Nd-Fe-B N42SH to N48UH (High Temperature Grade)
- Wind power generator (direct drive PMSG) → Nd-Fe-B N48H + Dy content adjustment
- General home appliance BLDC, car wiper → Ferrite Y30BH ~ Y35
- High temperature pump, aerospace actuator → SmCo 2:17 (28 ~ 32 MGOe)
- MRI auxiliary magnet, precision sensor → Nd N42 to N45 (enhanced coating)
Hellomag's Quotation Guide
Hellomag provides an RFQ form that allows simultaneous comparison of quotations for each of the three magnet grades above. Just tell us the usage environment (maximum temperature, motor type, magnetic flux requirement) and we will suggest an appropriate rating.
- Quote inquiry: parkdockyu@hellomag.co.kr
- Tel: +82-10-8990-0603
- Headquarters: Room 703, Building 203, 397 Seokcheon-ro, Ojeong-gu, Bucheon-si, Gyeonggi-do
Original source of this article: Hellomag — https://hellomag.co.kr