What is demagnetization?
There are situations in which magnets must lose their magnetic properties: for example, when the tools in the workshop otherwise attract iron chips or other building components. Or when ships used for military purposes have absorbed too much magnetization from the earth's magnetic field and otherwise run the risk of being damaged by magnetic mines.
In those cases, permanent magnets are demagnetized with a strong alternating magnetic field - this process continues until the coercive field strength of the material has been reached. As a result, magnets partially or completely lose their magnetic polarizations.