How Does a Rare Earth Magnet Work?

A rare-earth magnet is a particularly strong magnet that must contain materials such as iron, cobalt, and nickel. These are the only elements available that are ferromagnetic at room temperatures. Ferromagnetism is one of the strongest types, as opposed to forms such as diamagnetism and paramagnetism. It involves forces created by the movement of electrons within atoms with magnetic moments in the electrons originating from the orbital motion of the electron and the electron's spin on its own axis. In the ferromagnetic properties of rare-earth magnets, the crystal structure of the materials cause the magnet to be much stronger than ordinary magnets.

High-quality rare-earth magnets can have an attraction that is 1,000 times the weight of the magnet itself. The range in quality, though, depends on how the magnet is manufactured. These types of magnets are mainly derived from ceramic, alnico, neodymium and samarium cobalt. One of the strongest ones is nickel-plated neodymium magnets, small units that can lift a 10-pound block of steel.

Just what does magnetic strength mean and how is it measured? This is first deduced by figuring out the ability of a specific alloy to be magnetized. Gauss per cubic inch of material measures the intensity of a magnetic flux. Another feature is called oersteds, which is a measurement of the magnet's coercivity, or how much the magnet resists weakening. Rare-earth magnets have the most resistance of all magnets. The modern method of determining the magnet's strength is to multiply both the Gauss per cubic inch and oersteds. The unit obtained from this is known as an MGOe, or megagauss oesterids. To compare materials, a carbon steel magnet has an MGOe of 0.25, while a rare-earth alloy has an MGOe of 50. That is quite a difference.

Rare-earth magnets have many functions. They can hold together bits on industrial tools without the need for epoxies. They also hold storage boxes in place or keep tool boxes temporarily in place on a tractor at a farm. If the magnet needs to be stronger, a cup can be fitted onto it. A cup shape at the end of the magnet increases its strength four times. Washers can also be used to increase the attractive force of the magnet.

References

• Rare Earth Magnetics Website
• Lee Valley & Veritas, About Rare-Earth Magnets