Effect of temperature on Magnets
Heating

When the temperature of an element increases, its atoms vibrate. In a magnetic element, the vibration of atoms weakens the alignment of the magnetic domains of which they are part. As the alignment of an object's magnetic domains weakens, its electromagnetic force decreases. Therefore, the higher the temperature of a magnetic object, the less magnetic it will be. However, the magnetic domains of an object generally realign when it returns to room temperature and its atoms cease vibrating. The object will regain its full magnetism unless it was heated beyond a certain temperature (Curie Temperature).

The below graph shows a simple experiment with Neodymium normal grade magnets (max. operating temperature of 80 Deg C) and its ability to pick up steel washers when it is preheated to certain temperatures.

If your application requires a higher temperature grade of Neodymium magnet, you may opt for a
Neo 15x10mm disc ND1510-N35EH which can sustain upto 200 Deg C or the Neo 20x10mm disc ND2010-N44SH
which can operate at 150 Deg C.

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Magnetism vs temperature

Curie Temperature


Each magnet has a temperature, known as the Curie (named after Marie Curie) Temperature, which, when reached, can permanently remove its magnetism. When a magnet is heated but does not reach the Curie Temperature, its magnetic strength returns to normal when it regains its normal temperature. The Curie temperature is the critical point where a material's intrinsic magnetic moments change direction. Magnetic moments are permanent dipole moments within the atom which originate from electrons' angular momentum and spin. Materials have different structures of intrinsic magnetic moments that depend on temperature. At a material's Curie Temperature those intrinsic magnetic moments change direction.

Cooling

A magnet is an electron or group of electrons circling a nucleus within a material. When a magnetic material is cooled the electrons move slower, ordering the movement of the electrons and increasing the magnetism of a material.

Magnet strength with Colder temperature