DEMAGNETIZATION

Demagnetization refers to the process of partially or completely reducing the magnetic properties of a component (ferromagnetic material). The aim is to achieve values below 4 A/cm.

PROCESS

Materials are usually demagnetized by an attenuating alternating magnetic field. This magnetic field must initially be strong enough to reach the coercive field strength of the magnetized material. The alternating field causes the permanent magnetic materials to be remagnetized with decreasing amplitude. This causes the hysteresis curve to be traversed with decreasing amplitude of the magnetic field strength and magnetic flux density until the permanent magnetic field is zero.

In the adjacent image, for example, the process begins at the top right, then moves counterclockwise to the bottom left, then back to the top right, but not as far, etc. After many cycles, when the smallest loop at the intersection of the two axes is reached, the external magnetic field can be switched off and the iron is largely demagnetized.

There are two methods for attenuating the alternating field: either the object is slowly removed from the constant magnetic field, or the magnetic field decreases as a result of current reduction. Usually, 5 to 10 magnetizations are sufficient.

Demagnetization can also be achieved by mechanical vibrations or by heating the ferromagnetic materials above the Curie temperature.