Id cards may be degaussed when placed with magnets. Degaussing: When the magnetized material is affected by external energy, such as heating and impact, the magnetic distance direction of each magnetic domain will become inconsistent, and the magnetism will weaken or disappear, this process is called degaussing. There is also a common method: put the material with magnetic retention in the AC magnetic field, gradually weaken the AC magnetic field strength until it disappears, and the material is degaussed.