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What Could You Do To Demagnetize A Permanent Magnet?

What is a permanent magnet?

 

A permanent magnet is a magnet with magnetic fields around it continuously. Magnetic fields are powerful. While they're invisible to the naked eye, they have a variety of applications and capabilities that extend far beyond just holding up notes on the fridge. Whether it's helping to drive the motors inside an MRI machine or increasing efficiency in an electric motor, magnets play a vital role in bringing modern technology to life. Neodymium magnets are among the strongest magnets in the world. Invented more than 40 years ago, their utility ranges from tiny medical devices to large wind turbines. Their magnetic field is produced by electrons that spin in a circular motion; these spins align and create magnetic fields that attract or repel each other.

 

What is Demagnetization?

 

A phenomenon occurs when a magnet is subjected to a changing magnetic field. Rapid changes in field direction can cause the domains on a magnet to partially or completely "flip" from one orientation to the opposite orientation.

Magnetic fields are something you would want to avoid when it comes to your watch. Exposure to strong magnetic fields will make your watch attract metal objects, and magnetization may be impossible to remove. If a watch comes in contact with such a magnetic field, it will become magnetized. The best way to remove this magnetism is by using an Anti-Magnetizer.

Demagnetization is one of the most important processes in metallurgy, turning the solid metal into a malleable one. The process involves heating past the Curie point, applying a strong magnetic field, applying alternating current, or hammering the metal.

 

What is Curie temperature?

 

The Curie temperature is the temperature at which magnetic spins stop aligning. It is named for the French physicist Pierre Curie, who discovered the phenomenon in ferrimagnets.

The Curie temperature is when any permanent magnet loses its magnetism. Named for the French physicist Pierre Curie, this critical temperature is based on the magnetic moment of iron atoms and the spin magnetic moment of electrons. The Curie temperature depends on the chemical composition and increases with any impurities.

The Curie temperature is the temperature at which a material loses permanent magnetism. The average Curie temperature of a ferromagnetic material is 600 to 800°C, depending on the material, with anti-ferromagnets having a negative Curie temperature.

 

What is the Effect of Heat vs. Cold on a Permanent Magnet?

 

Heat exposure and extreme temperature changes are two of the biggest threats to magnetic materials. When exposed to heat, these materials experience a process called thermal expansion. As a result, their atoms become unstable and are no longer capable of sticking together or functioning properly. Therefore, a magnet will no longer withstand high temperatures and will eventually lose its strength entirely. On the other hand, cold strengthens the magnetic field. However, although ferrite magnets can withstand high temperature up to 150 °C, it cannot withstand very low temperature. According to authoritative test data, ferrite magnets will begin to demagnetize in an environment of minus 40 °C. Therefore, in places with cold weather, such as communication wires, cameras, etc., most of them are rare-earth magnets such as SMCO magnets and NDFEB magnets.

Magnets can be destroyed by hitting the magnet in the north and south poles. If these poles are ruined, the magnetic force will weaken dramatically.

 

Permanent Magnet-01       Permanent Magnet-02

 

Reverse Field

 

The magnetic field of a magnet can be removed by passing a strong electric current around the magnet. Hence, the magnetic field will disappear while the magnet becomes electrically charged to neutralize the applied current. When this happens, the magnet becomes magnetic again, but opposite. This process can be achieved by placing a magnetized magnet in a coil winding with a sufficient number of turns (this winding coil is the magnetizing coil). When the coil conducts enough current instantaneously around the magnet, a strong enough magnetic field will be generated and magnet will lose its magnetic field for that time and become opposite in normal condition.

 

Effect of Room Temperature

 

Over time, any magnet will lose its magnetism from the influence of its surroundings. This process is known as demagnetization over a room temperature. As heat can increase the rate at which a magnet loses its magnetic properties, let’s say a permanent magnet under influence of room temperature will lose its magnetic strength over a long period of time. Although this process can take up-to years depending up on the strength, the room temperature degree and material used to create a magnet.

 

What Are The Advantages Of Demagnetization?

 

Demagnetization is a powerful, non-destructive technique for removing unwanted magnetic fields from components. When parts are magnetized either unintentionally or because they were manufactured to specifications that contained too high a level of magnetic material, demagnetization can restore their original function and performance. Components made from ferromagnetic materials have become indispensable tools in a wide range of industries.

However, there is also a serious downside. Because these components are subject to magnetic fields, they are prone to damage by external influences, such as strong magnets and current-carrying cables. This means that complex (and expensive) measures must be taken to protect them.

Hence demagnetization is useful.

 

What Are The Disadvantages Of Demagnetization?

 

As magnets are used in almost daily life and gadgets, if magnets are demagnetized either due to high temperature or a striking hammer, the magnet weakens its strength and becomes a useless piece of metal. Over time, permanent magnets which are put under a lot of stress will weaken; think about the use of a simple household magnet and how it loses power when you press on it for too long. High temperature and transforming the molecular structure of a magnet can demagnetize a rare-earth magnet. But these demagnetizing conditions don't happen in the normal course of regular life. For example, in a refrigerator of minus 18°C, magnets are subject to low temperatures and are unlikely to show negative magnetic coupling in years.

Note: Ferrite permanent magnets are different from other magnets and it will lose magnetism at -40°C.

 

Conclusion:

Permanent magnets are permanent because they have magnetic fields that do not disappear and keep attracting any metals in their surroundings. They are especially strong. But the strength of a permanent magnet can be weakened until the end when the temperature matches a magnet's Curie temperature. Curie temperature is when any permanent magnet loses its magnetism, or magnetic property alters. 18°C

The methods involved in demagnetization are simply easy and are considered an effective step in the metallurgy process. The process involves heating past the Curie point, applying a strong magnetic field, applying alternating current, or hammering the metal.

 

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