Magnets are very useful in many fields, many places in daily life, … but sometimes they cause trouble because of it. There are the following ways to limit or completely eliminate the attraction of a magnet:
- Use an iron box
- Use heat
- Use a demagnetizing device
1. Use an iron box
The property of iron is to conduct magnetism, taking advantage of this property, we can cover the iron around the magnet, then the lines of force of the magnet will be conducted and closed on the iron box, not running into the surrounding space. And thus losing the attraction of the magnet.
2. Use heat
When the temperature of the magnet increases, the molecules move chaotically, when it increases above the Curie temperature (T > Tc), the motion energy is greater than the exchange interaction energy, the magnet will lose its orderly state and switch to a paramagnetic state with chaotically oriented magnetic moments. Therefore, the magnetic properties of the magnet are completely lost. For a magnet, when its temperature is greater than the Curie temperature, it is completely demagnetized. When using magnets in high temperature environments but lower than Tc, the magnetism of the magnet will decrease. Curie temperature, or Curie point (often denoted as Tc, is a concept in solid state physics, materials science is the phase transition temperature in ferromagnetic or ferroelectric materials, named after the French physicist Pierre Curie (1859 – 1906). Curie temperature in ferromagnetic materials is the temperature of the ferromagnetic – paramagnetic phase transition. Below the Curie temperature, the material is ferromagnetic, above it, the material will lose its ferromagnetic properties and become paramagnetic. For rare earth magnets (white magnets), the Tc temperature is 320 degrees Celsius.
3. Using demagnetizing equipment
Principle: Place the magnet in a magnetic field to charge the magnet but with a smaller intensity, continuously reversing when the magnetic field reaches 0 will completely demagnetize.
For magnets with low residual magnetism, an alternating magnetic field can be used: At that time, the “small magnets” will reverse 180 degrees continuously according to the alternating frequency of the The electric current stimulates this magnetic field. We gradually reduce the current intensity, causing the magnetic field intensity to gradually decrease until it reaches zero, then the material will lose its magnetism.
