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Temperature changes a magnet’s output while it is hot and may also cause an irreversible loss after it cools. The grade suffix is only a screening clue. A usable temperature limit depends on the exact material, magnet shape, working point and opposing field in the assembly. Ask for the supplier’s demagnetization curves at the relevant temperatures and verify the assembled part at its worst-case condition.
How to read the table: the values below are indicative grade-family figures for a high working point, not guaranteed limits for every NdFeB part. Do not use the listed maximum as a stand-alone design rating. See Arnold Magnetic Technologies’ NdFeB data for grade-specific temperature properties and application considerations.
| MAGNET TYPE SUFFIX | Rev.Temp.Coef. of Induction (Br), a, %/°C (20-100°C) | Rev.Temp.Coef. of Coercivity (Hci), b, %/°C (20-100°C) | Max. Working Temperature |
|---|---|---|---|
| (based on High working point) | |||
| -0.12 | -0.6 | 80 ºC = 176 ºF * | |
| M | -0.12 | -0.58 | 100ºC = 212 ºF |
| H | -0.11 | -0.58 | 120ºC = 248 ºF |
| SH | -0.1 | -0.55 | 150 ºC = 302 ºF |
| UH | -0.09 | -0.52 | 180 ºC = 356 ºF |
| EH | -0.085 | -0.5 | 200 ºC = 392 ºF |
| VH / AH | -0.08 | -0.45 | 230 ºC = 446 ºF |
| * 60 ºC for N50 and N52 |
“High-temperature magnet” is a design requirement, not a material label. NdFeB, SmCo, ferrite and AlNiCo have different magnetic output, temperature behavior and demagnetization resistance. A maximum temperature quoted for one grade or geometry should not be applied to every magnet in that family.
If an NdFeB option does not meet the required field after the full thermal cycle, compare a specified SmCo grade or another material against the same assembly requirement. Request grade-specific curves and a test on the finished assembly instead of selecting by a generic “up to 500°C” or “up to 650°C” claim.
The Curie temperature describes a material transition at which ferromagnetic ordering disappears. It is not the maximum service temperature for a finished magnet. An NdFeB part may lose magnetic output irreversibly well below its Curie point, depending on its grade and operating point. Arnold’s technical note on demagnetization curves explains why the load line and intrinsic curve matter in a temperature review.
The magnetic properties of NdFeB magnets are influenced by temperature. The temperature coefficient of remanence (α) and the temperature coefficient of coercivity (β) describe how the remanence (Br) and coercivity (Hc) change with temperature, respectively. Generally, these coefficients are negative, meaning that as the temperature increases, the magnetic properties decrease.
Check irreversible loss at the highest temperature and the least favorable working point in the actual magnetic circuit. Demagnetization can occur well below the Curie temperature. A thin part, an open-circuit condition or an opposing field may increase risk. Specify the maximum permitted loss after a defined temperature exposure and return to the reference measurement temperature; then test representative finished parts.
NdFeB magnets are affected by high temperatures and can also experience thermal demagnetization when subjected to thermal cycling. Repeated exposure to temperature variations can lead to a gradual loss of magnetic strength over time.
A larger N number describes a different magnetic energy product; it does not by itself mean better resistance to heat. Compare the required field at operating temperature with the grade’s intrinsic coercivity and demagnetization curve. Include the highest continuous and short-duration temperatures, the assembly geometry, any reverse field and the permitted irreversible loss in the inquiry. Review the selected coating and adhesive against the same thermal profile.
Send the drawing and temperature profile for a grade review.
The choice of coating for NdFeB magnets is also important. Some coatings are more resistant to temperature-related degradation and corrosion. Coatings can provide an additional layer of protection against environmental factors.
In summary, it’s crucial to consider the temperature effects on NdFeB magnets when designing applications that involve exposure to different temperature ranges. Proper selection of magnet grade, design considerations, and environmental protection can help mitigate the impact of temperature on the performance and longevity of NdFeB magnets.