1. Start with temperature, not strength
Neodymium loses coercivity as it heats. Past the grade's rated limit the loss becomes irreversible — cool it back down and the field does not come back. Rate the magnet for the hottest steady-state temperature it sees inside the assembly, then add margin for the working point of your magnetic circuit. Thin magnets in open circuits demagnetize sooner than thick magnets in closed loops at the same temperature.
2. Read the grade code
For neodymium the number is maximum energy product in MGOe — how much field you get per unit of volume. The letter suffix is intrinsic coercivity, which is really a temperature rating.
| Suffix | Max operating temp | Typical use |
|---|---|---|
| (none) | 176°F / 80°C | Room-temperature holding, consumer devices |
| M | 212°F / 100°C | Warm electronics, light-duty motors |
| H | 248°F / 120°C | Automotive underhood, pumps |
| SH | 302°F / 150°C | Traction motors, generators, sensors in heat |
| UH | 356°F / 180°C | Downhole tooling, heavy industrial actuation |
| EH | 392°F / 200°C | Extreme continuous duty |
3. Compare the materials we stock
| Grade | Material | Energy | Max temp | Notes |
|---|---|---|---|---|
| N40 | Neodymium | 40 MGOe | 176°F / 80°C | Cost-efficient general purpose |
| N42 | Neodymium | 42 MGOe | 176°F / 80°C | Most common stock grade |
| N45 | Neodymium | 45 MGOe | 176°F / 80°C | Higher flux, same envelope |
| N52 | Neodymium | 52 MGOe | 176°F / 80°C | Maximum strength per volume |
| N42SH | Neodymium | 42 MGOe | 302°F / 150°C | High coercivity, hot service |
| N45SH | Neodymium | 45 MGOe | 302°F / 150°C | Our high-temp workhorse |
| Sm2Co17 | Samarium Cobalt | 24–32 MGOe | 550°F / 288°C | Thermally stable, corrosion resistant |
| Ceramic Grade 8 | Ferrite | 3.5 MGOe | 480°F / 250°C | Low cost, high volume |
4. Neodymium or samarium cobalt?
Choose neodymium when
- · You need maximum field in minimum volume
- · Operating temperature stays under 300°F
- · Cost per gauss matters
- · A plated surface is acceptable
Choose samarium cobalt when
- · Service temperature exceeds 300°F, up to 550°F
- · Field must stay stable across a wide temperature swing
- · The part sees moisture, salt or chemicals unplated
- · Long-term drift must be minimal (RF, instruments)
5. Coatings
Neodymium corrodes if left bare, so it is plated. Nickel-copper-nickel is the default: hard, shiny, good for most indoor and sealed applications. Epoxy over nickel adds salt-spray life. Parylene and PTFE suit medical and food contact. Zinc is economical but softer. Samarium cobalt and ceramic are inherently corrosion resistant and normally ship uncoated.
6. Pull force is a system property
Published pull force assumes a thick, flat, clean mild steel plate in direct contact. Add a 0.010" air gap, a thin target, paint, or a lateral load and real-world holding drops fast — often by half. Tell us the target thickness and the working gap and we will calculate the force you will actually see.
Not sure which grade fits?
Send the operating temperature, geometry and the field or force you need. We will specify the grade and quote it — call 574-633-0061 or send it in writing.