How to Demagnetize a Magnet

How to Demagnetize a Magnet

What is Demagnetization?

Demagnetization is the process of removing strength or destroying properties from a magnet. That is, after this process, a permanent magnet or electromagnet loses all its magnetic properties.

Reasons for Demagnetizing Magnet

  1. Magnets at times are undesirable for example magnetic tape drives or other data storage and would want anyone to access the data. Demagnetization can be one of the ways to remove data and improve security.
  2. Some of the metallic objects can become magnetic causing problems, like you can find metal attracts other metal. In other cases, you can find magnetic field itself presents issues that are mostly demagnetized and they include flatware
  3. To remove magnetism from something that has become magnetized.
  4. To randomize the orientation
Reasons for Demagnetizing Magnet NEW
Static Demagnetization vs Dynamic Demagnetization

Static Demagnetization vs Dynamic Demagnetization

There are three critical aspects you need to note about these types of demagnetizations:

  1. Static demagnetization magnetic field opposite is added in the original direction of the magnet. While dynamic demagnetization a sufficiently strong alternative of magnetic field is applied.
  2. Static demagnetization the strength of an anti-magnetic field should ensure that magnetic induction intensifies the magnet making the body become zero when removed. While dynamic demagnetization the magnetic field is demagnetized by decreasing the hysteresis loop.
  3. In static demagnetization, the magnetically neutral state is referred to as the static magnetically neutral state. While dynamic demagnetization the resulting neutral state is called the dynamic magnetically neutral state.

Common Effective Demagnetization Processes

Method 1: Heating Magnet/Thermal Demagnetization

Once a magnet is heated past the temperature called Curie point it frees the magnetic dipole from ordered orientation. Curie point temperature is a point beyond which a magnet loses permanent magnetic properties. Therefore, heating permanent magnets beyond Curie’s temperature will make them lose their magnetic properties.

Here is a brief guideline of various Curie points for most common magnets:

Magnet Type Approximate Operating Temperature (°C) Estimated Curies Temperature (°C)
Neodymium Magnets (NdFeB Magnets) ·         150 ·         310 to 400
Samarium Cobalt Magnets (SmCo Magnets) ·         310 ·         700 to 800
Alnico Magnets ·         525 ·         800
Ferrite Magnets or Ceramic Magnets ·         250 ·         450

 

Curie’s point has different importance:

  • When any magnet is heated above Curie temperature it loses its magnetic properties
  • It can cause dipole to be misaligned causing demagnetization when heated across the Curie point.
  • It can cause an intrinsic magnetic moment within it to change direction.

According to the ordered orientation, the long-range one is destroyed and will have little to no magnetization.

The reason why you can demagnetize a permanent magnet by heating is that if it is heated at an appropriate temperature the heating may cause the orientation of domain on the magnet. Depending on the degree of heating, it can cause temporary loss or complete loss of magnetic properties.

Method 2: Hammering magnet/Striking magnet

Hammering can be done to a magnet by dropping it or continuously hitting it on a hard surface. By doing that it will shake the order of material making it to be demagnetized. When it is hammered the dipole gets disturbed and loses its orientation making the magnetic moment not exist.

Method 3: Applying AC Current

Applying AC Current is one of the ways to make a magnet by applying an electrical field. AC can be used to demagnetize a magnet through a coil placed near the magnet.

When the magnetic field is passed through the coil wrapped around the magnetic object the magnetic domain will be randomized. This effectively demagnetizes magnets.

Self-Demagnetization

It is the process by which the magnet demagnetizes itself by opposing fields created within its magnetism.

Self-demagnetization can be prevented by using magnetic keepers which are two soft iron bars each on every pole of the magnet.

When the magnet is stored together or rubbed against each other changing the orientation of the magnetic dipole, it may reduce magnetic field strength.

Reversed Magnetic Field

When a magnet is exposed to increase the temperature length within a given time, electrons are forced out of alignment and the magnet will be demagnetized in a reversed way.

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