The magnetic material can be magnetized in the following way:
The material is heated above the Curie temperature, cooled in the presence of an applied magnetic field, and beaten by the material during cooling. This is the most effective way of magnetizing, and is similar to the way permanent magnets are made in the industry.
The material is placed in an applied magnetic field, when the magnetic field is removed, the ferromagnetic material will still have a magnetic field, called residual magnetism. If there is an external magnetic field vibration material, the effect will be better.
If a magnet is repeatedly moved from one end of the material to the other, it can also help magnetize it.
Magnetized ferromagnetic materials can be demagnetized in the following ways:
Heating above the Curie temperature, molecular motion can destroy the magnetic domains of the material and eliminate all magnetism.
Place the material in a changing magnetic field whose H-field intensity exceeds the coercivity of the material and then slowly move the material out of the field or slowly reduce the field strength to zero. This is the principle that the demagnetizer demagnetizes the device and the credit card, and the demagnetization coil in the cathode ray tube.
If the magnet is placed in a reverse magnetic field where the magnetic field strength is greater than the coercive force, the magnet may be partially demagnetized but it may also be magnetized by the reverse magnet.
Hammering or bumping: Mechanical disturbances disturb the magnetic domains and also reduce some of their magnetism.
Article from NdFeB Industry Network