Neodymium magnets are called permanent — but only under the right conditions. Treat one badly and it quietly loses strength. Three things cause most demagnetization, and all three are easy to avoid once you know them.
Enemy 1: heat
Every grade has a maximum working temperature. Push a magnet past it and it starts losing flux; beyond a certain point the loss is permanent. The fix is choosing the right grade — the letter at the end of the name (N, M, H, SH, UH, EH, TH) tells you how much heat it can handle. And heating a magnet above its Curie temperature, roughly 350 °C for NdFeB, destroys the magnetism completely; cooling it back down does not bring it back.
Enemy 2: opposing magnetic fields
Bring a magnet near another magnet's opposite pole, or inside a coil or motor winding, and the opposing field can flip parts of its internal magnetic structure. The magnet does not need to touch anything — magnetic fields act through air. A strong opposing field can erase a magnet partially or completely.
Enemy 3: mechanical shock
NdFeB is brittle. A hard knock, drop or hammer blow can disturb the magnetic structure near the surface and cause local loss. Handle magnetized parts gently.
How to protect your magnets
- Pick a grade with working-temperature headroom for your application.
- Keep magnets away from strong opposing fields and store them in a safe layout.
- Never drop, hammer or force magnetized parts.
- If performance matters, verify with a gaussmeter — a magnet that quietly lost 10–20% of its strength looks fine but performs badly.
A demagnetized magnet can be re-magnetized with a strong field, but not perfectly — in critical applications, replace it.
Read on: temperature behavior → · grades explained →