Demagnetization Way

Hard magnetic materials (such as NdFeB) have two notable characteristics, one is that they can be strongly magnetized under the action of an external magnetic field, and the other is hysteresis, that is, hard magnetic materials still retain their magnetized state after the external magnetic field is removed. So how do you demagnetize a magnet that has been magnetized to technical saturation? Today we will learn about the principles and methods of demagnetization.

Demagnetization, also known as magnetic cleaning, degaussing, etc., refers to the process of restoring a magnet to a magnetically neutral state, also known as magnetic neutralization.

In industrial processing, there are three methods of demagnetization:

1. Static demagnetization

Add a magnetic field opposite to the original magnetization direction of the magnet. The strength of this anti-magnetic field should ensure that when it is removed, the magnetic induction intensity of the magnetic body becomes zero. The resulting magnetically neutral state is referred to as the static magnetically neutral state.

In the hysteresis loop curve, the blue line b-c segment in the second quadrant represents the demagnetization curve, that is, when the magnet is applied with a magnetic field opposite to the magnetization direction, its magnetic induction decreases with the increase of the reverse magnetization field strength. When the strength of the magnetizing field reaches -Hc, the magnetic induction intensity of the magnet drops to 0, and the magnet is no longer magnetic.

The hysteresis loop is measured at room temperature, and the demagnetization curve of the magnet is not the same at different working temperatures, as shown in the figure below. Therefore, the strength of the reverse magnetic field applied for demagnetization under different temperature states is different.