Can a Neodymium Magnet Be Demagnetized or Remagnetized?
Yes, but not easily. Neodymium magnets resist demagnetization far better than ferrite (ceramic) and alnico magnets. Heat is the usual cause: above its maximum working temperature, 80 °C (176 °F) for standard N grades, a magnet loses some strength for good, and at its Curie point (about 310 °C) it loses all of it. Remagnetizing takes an industrial magnetizer, so replacing a damaged magnet is usually the practical fix.
See maximum operating temperature vs. Curie temperature for how the two limits differ.
What Weakens a Neodymium Magnet
Heat Above Its Rating
The most common cause. A magnet left on a grill, in an engine bay or on a dashboard in summer sun can pass 80 °C. If you need heat resistance, choose a high-temperature grade.
Strong Opposing Fields
Forcing large magnets together north to north, or running magnets in motors that overload, can partly demagnetize a thin magnet, especially when it’s warm.
Corrosion
Rusted material is no longer magnetic. Once plating is chipped, moisture eats into the magnet. See will neodymium magnets rust?
Physical Damage
Chips and cracks don’t demagnetize the material, but every lost piece takes some strength with it.
What Doesn’t Weaken Them
- Time. At room temperature, a neodymium magnet loses only a tiny fraction of its strength over decades. See will neodymium magnets lose their strength over time?
- Sticking to steel or other magnets. A magnet stuck to a fridge or a stack isn’t being used up.
- Dropping. Unlike old steel magnets, neodymium won’t lose magnetism from a knock, though it may chip.
- Tool and watch demagnetizers. These handheld devices are far too weak to affect neodymium. The material resists opposing fields of over 11,000 oersteds (its coercivity, Hci).
Can I Demagnetize a Magnet on Purpose?
It takes heat past the Curie point (about 310 °C) or an industrial demagnetizer, and neither is practical at home. There’s rarely a reason to: for disposal or recycling, simply keep magnets contained so they can’t snap onto other metal or be swallowed. If you need part of a magnet’s field blocked, shield it with steel instead (see what blocks a magnetic field).
Can a Magnet Be Remagnetized?
Yes, with the right equipment. Factories magnetize neodymium with a capacitor-discharge magnetizer that produces a brief pulse of roughly 3 tesla (30,000 gauss) or more. No permanent magnet comes close to that, so you can’t recharge one magnet with another.
Two Limits on Remagnetizing
- Direction is set at the factory. Neodymium magnets are pressed with their grains aligned in one direction. An axially magnetized disc can be remagnetized axially (either way round), but it can’t be turned into a diametric magnet.
- Heat damage may not fully recover. Remagnetizing restores loss from heat or opposing fields, but not loss from corrosion, chips or structural changes from severe overheating.
For a few magnets, replacing them costs far less than remagnetizing. For production quantities, ask us about custom magnets in a grade that suits your temperature.