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How To Demagnetize A Magnet

A magnet is demagnetized by bringing it in contact with any substance capable of stripping it of its magnetic field strength. Demagnetization causes a magnet to lose its power due to a change in the arrangement of the electrons making up its magnetic field. Imagine an elastic material pulled beyond its limits, leading to the deformation of the material, rendering it plastic. Likewise, a magnetic material will become non-magnetic when external factors such as heat or blunt force affect the electron alignment of the material.

Can a magnet be demagnetized?

Magnets, permanent or temporary, can lose their magnetism, though they respond differently to substances that exert demagnetization. A permanent magnet retains its magnetic abilities over a long period of time. Most permanent magnets reject the influences of a demagnetizing object and should emit a strong magnetic field at a low mass. Neodymium magnets are some of the strongest permanent magnets known.

Temporary magnets are pseudo magnets. They can behave as magnets when in contact with other magnets or materials that produce a magnetic field. Once disconnected from these substances, they lose their magnetism and return to their plastic states. If you bring an iron nail with a wide radius towards a strong magnet, the nail becomes charged and can attract other iron nails due to its acquired magnetic field. Unlike their permanent counterparts, temporary magnets have no resistance to demagnetization.

Why demagnetize a magnetic material?

Not all magnetic materials are fitting for every application. In some instances, magnetism must be nullified for a task to be completed or corrected. The most relative examples are the destruction of a storage disk, the removal of a wristwatch’s magnetism, and the blunting of work tools for magnetism-sensitive environments.

Storage disks such as hard drives can be stripped of their magnetism to enhance data destruction. Though this isn’t frequent (because people don’t wake up wanting to destroy their hard drives), demagnetizing can cause the drive to lose a significant part of its data. Arguably, this isn’t the most efficient erasing a drive’s data. If you don’t want anyone to access your data, you should subject it to the force of a hammer or rock.

Watches have magnets, too. You didn’t know? Proximity to a magnet can toy with the tiny magnetic components that make your watch tick. If you observe that your magnet has gained or lost extra minutes, you can hold a magnet accountable for this. Magnetic altering isn’t peculiar to wristwatches; mobile phones, hair dryers, television, and microwaves are other appliances and gadgets having magnetic components.

To prevent your watch from running ahead of you, regularly demagnetize it. You don’t have to visit a horologist to get this done. A tool like a degausser machine will do a great job of removing any magnetism from your watch. You can check for magnetism by bringing your watch close to a compass. Did the contact move the compass needle? Great, your wristwatch has acquired some magnetism. Other preventive measures include removing your watch whenever you handle magnetic substances (phones, loudspeakers, hair dryers, or even a quick trip to the hospital for a scan).

Some work tools are sensitive to magnetic surroundings. An example is a screwdriver, which can function as a temporary magnet if connected to a strong magnetic field. But, you may want to demagnetize your screwdriver if you are working on appliances or gadgets whose magnetism must be preserved. Bringing your screwdriver against a hard drive may erase the data on the drive, and if you didn’t plan to clean your hard drive, this might be a hard loss. To demagnetize these work tools, apply blunt forces against their edges, altering their volume and shape.

How to demagnetize magnets

Demagnetization is facilitated by the altering of the physical properties of a magnet. Factors that enhance demagnetization include:

Volume loss

Volume loss is reckoned as the most effective way to demagnetize a magnet. The surface area of a magnet is proportional to the magnetic field it induces. Reduced mass will result in magnetism’s reduction or partial elimination. Though there are many ways to cause this, corrosion is the most common. Corrosion is triggered by the reaction of oxygen with the chemical components of the magnet, resulting in air fractures within it. When these fractures accumulate, they affect the compactness of the magnet, reducing its total volume.

Loss of magnetism due to volume shrinkage can also happen if a part of the magnet is chipped away from the main magnet. When this happens, the magnets should undergo professional testing to determine what caused the breakage and check for magnetism or lack thereof.

Change in magnetic geometry

Magnets have magnetic geometry, affecting their ability to resist or allow demagnetizing influences. Magnets whose geometries conform to ideal standards are more capable of preserving their magnetism and rejecting elevated temperatures,

Magnetic geometry is calculated by comparing the magnetic length to the diameter (L/D). The magnetic length is the measurement of the physical dimension of the magnet concerning the lines of magnetism. Diameter is deduced from the diameter of the magnetic pole, or the diameter corresponding to the area for non-circular poles. To do this, locate the center of the pole, find the area, and then calculate the diameter within that area.

Generally, the larger the L:D, the more resistant a magnet is to demagnetization. To increase the L:D, manufacturers boost the volume of magnets, increasing the overall production costs. However, a change in the L:D of a magnet will not always guarantee increased resistance. Once a magnet reaches its peak resistance level, any further addition will cause diminishing marginal returns. The increase will not affect the magnet’s resistivity to demagnetization.

Temperature

Magnets have an operating temperature within which they are at optimum function. This is known as the Curie temperature, and anything beyond this makes them vulnerable to demagnetizing influences. The Curie temperature for some magnets are:

  • Iron (770 degrees Celsius).
  • Neodymium (320 degrees Celsius).
  • Cobalt (1115 degrees Celsius)

When a magnet is heated, its strength inevitably decreases, but the magnetism is restored on cooling. Further heating of the magnet above its limit will render it “magnetically plastic.” The Curie temperature is for magnets, and the yield limit is too elastic for materials. When this happens, the recovery of the magnetism requires a manual re-magnetization, unlike the case with temporary losses.

The magnet’s geometry, discussed in the previous section, affects a magnet’s ability to resist magnetism. The L:D can be tested in industrial settings to see if it is sufficient from extreme temperature stretches. If balanced, a magnet can perform under the maximum operating temperature advertised by its manufacturers.

Do you frequently use magnets for high-temperature projects? Don’t rely on the temperature ratings alone. Consult an expert to understand the magnetic length to diameter ratio and compare the findings with the environmental setting in which the magnet will be used.

Time

Magnets degrade with age. Inspect a random magnet, and you won’t notice that its atoms are constantly in motion. These motions are affected by movement, application of heat, and impact of force.

Since the temperature of any degree affects a magnet, even the mildest temperatures will demagnetize a magnet just a little bit. This means that over a long period, magnets eventually wear out and become less potent. This time-lapse varies with magnets and the substances with which they’ve been made. Neodymium magnets often last one century, and samarium-cobalt magnets will retain magnetism for up to 500 years.

Coercivity and resistivity are two properties that can adequately suggest how long a magnet will be at high performance.

Another magnetic field

Magnetism is infused into a magnet in the direction of the magnet’s orientation. When an external field having an opposite orientation acts on a magnet, the orientation of the magnetic field changes. During reorientation, the magnets become weaker. This demagnetization is often partial and will reduce the effectiveness of the magnetic material.

An electromagnet, coil, or other permanent magnets can impose demagnetization due to external fields. This is why magnets are not stored with their north poles parallel to one another, as this will reduce magnetism. When the north poles are brought to touch, the magnets attract one another, and overall magnetic strength is reinforced.

Conclusion

Extreme temperatures can collude with external magnetic fields to completely strip a magnet of its magnetism. Though this isn’t a common experience in industries or homes, combining both factors will inevitably render the magnet weak.

As you purchase magnets, plan effective storage mechanisms. Invest in quality magnets, and shop with suppliers or manufacturers committed to shipping out the best quality available. Are you looking to purchase your next box set? Contact us for expert guidance. We are excited to help you make the right choices.

 

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Article by

ROBO Magnetic Product Team

We are the manufacturer with 16 years of experience in custom neodymium magnets.

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