Demagnetization

Demagnetization is the reduction or elimination of magnetization. It can be achieved by heating the object above its Curie temperature, where thermal fluctuations have enough energy to overcome exchange interactions, the source of ferromagnetic order, and destroy that order. Another way is to pull it out of an electric coil with alternating current running through it, giving rise to fields that oppose the magnetization.　Demagnetization is caused by armature reaction. It must be avoided when running a motor using a permanent magnet.