Rare earth Magnets including high power neodymium magnets that have lost their magnetism due to overheating can be re-magnetized.

Demagnetization from Overheating

Neodymium rare earth magnets become demagnetized when heated above their Curie temperature, which is around 80°C for neodymium magnets.
At high temperatures, the magnetic domains within the neodymium magnet become randomly oriented, causing the magnet to lose its overall magnetic field.

Demagnetization using demagnetizer
magnets can also be demagnetized using a demagnetizer.

Reversible Process

However, this demagnetization is reversible. Once the magnet cools down, the magnetic domains can be realigned through a process called re-magnetization, restoring the magnet's magnetic field strength.

Re-magnetization Methods

Common techniques to re-magnetize magnets include:

Exposing them to a strong external magnetic field from an electromagnet or another powerful permanent magnet.
Running an electric current through a coil wrapped around the magnet.
Placing the magnet in a strong magnetic field while cooling it down from above the Curie temperature.

Factors Affecting Re-magnetization

The effectiveness of re-magnetization depends on several factors, such as the magnet material, the previous heating temperature, and the specific magnetizing method used.
In some cases, magnets may not regain 100% of their original strength after severe overheating.

Summary
While overheating can cause neodymium magnets to lose their magnetism by disordering their magnetic domains, this process is reversible. By employing proper re-magnetization techniques once the magnet has cooled down, the magnetism can typically be restored, although the degree of recovery may vary.