1. Thermal demagnetization is to heat the sample above the Curie point and then slowly cool to room temperature without external field conditions. Although the operation of this method is complicated and may result in a change in the structure of the sample, it can achieve a complete demagnetization effect.
Curie point, also known as Curie temperature or magnetic transition point, refers to the temperature at which a material can change between a ferromagnetic body and a paramagnetic body, that is, a phase transition temperature at which a ferromagnetic body changes from a ferromagnetic phase to a paramagnetic phase.
2. AC demagnetization is the addition of a low frequency alternating magnetic field to the sample and its amplitude is uniformly reduced from a certain maximum to zero. AC demagnetization is divided into DC commutation demagnetization and AC demagnetization under power frequency.
At present, the AC demagnetization method under power frequency is widely used. Due to the specific operation process, there is a difference in the speed of the magnetic field or the magnetic induction of the sample. Experiments show that uniform demagnetization by magnetic induction is a better demagnetization method.