What happens when a magnet is heated?

Magnetic materials should maintain a balance between temperature and magnetic domains (the tendency of atoms to spin in a certain direction). However, when exposed to extreme temperatures, this balance becomes destabilized and the magnetism suffers. While cold increases the strength of the magnet, heat causes the magnetic properties to degrade. In other words, too much heat can completely destroy the magnet.

the physics behind it;

While increasing the temperature, the Magnetic Material will lose its magnetization up to a certain limit. As the atoms accelerate, the percentage of magnetic domains spinning in the same direction decreases. Beyond this limit, the magnet becomes a non-magnetic material, and this temperature limit is called the Curie temperature.

In addition to this, the magnetic dipole is changing its orientation, which depends on the spontaneous magnetic moment of the ferromagnetic substance, which is called magnetism.

When the temperature decreases, the magnetic moment increases and the magnet heats up. When the Curie temperature is reached, the spontaneous magnetic moment decreases and becomes zero. The magnetic moment of ferromagnetic substances will also be affected by many factors, such as external magnetic fields.

If you want to make physical observations, do this simple experiment:

Bring a magnet and some small nails.

First take the Bar Magnet and check if it attracts the iron pin, if so then the bar magnet is ok, if not replace the magnetized one.

Now take a bowl full of water and dip the magnet bar in it.

Start heating the device on the stove, or place a thermometer in the bowl to watch the readings.

If your reading exceeds 176 degrees Fahrenheit or 80 degrees Celsius, stop heating.

Now take the magnet and hold it close to the nail.

You will find that the nails are no longer attractive, which confirms my explanation, so when the magnet is heated, the magnetism becomes weaker.

This observation fits perfectly with Curie's law, which states that in paramagnetic materials, the magnetization of the material is (approximately) proportional to the applied magnetic field. However, if the material is heated, this ratio decreases. For a fixed value of the magnetic field, the magnetization is (approximately) inversely proportional to the temperature.