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Permanent Magnets

There are typically four categories of permanent magnets: neodymium iron boron (NdFeB), samarium cobalt (SmCo), alnico, and ceramic or ferrite magnets.

Neodymium Iron Boron (NdFeB)

This type of magnet is composed of rare earth magnetic material and has a high coercive force. They have an extremely high energy product range, up to 50 MGOe. Because of this high product energy level, they can usually be manufactured to be small and compact in size. However, NdFeB magnets have low mechanical strength, tend to be brittle, and low corrosion-resistance if left uncoated. If treated with gold, iron, or nickel plating, they can be used in many applications. They are very strong magnets and are difficult to demagnetize.

Samarium Cobalt (SmCo)

Like NdFeB magnets, SmCo magnets are also very strong and difficult to demagnetize. They are also highly oxidation-resistant and temperature resistant, withstanding temperatures up to 300 degrees Celsius. Two different groups of SmCo magnets exist, divided based on their product energy range. The first series (Sm1Co5) has an energy product range of 15-22 MGOe. The second series (Sm2Co17) has a range that falls between 22 and 30 MGOe. However, they can be expensive and have low-mechanical strength.

Alnico

Alnico magnets get their name from the first two letters of each of three main ingredients: aluminum, nickel, and cobalt. Although they feature good temperature resistance, they can easily be demagnetized and are sometimes replaced by ceramic and rare earth magnets in certain applications. They can be produced by either sintering or casting, with each process yielding different magnet characteristics. Sintering produces enhanced mechanical traits. Casting results in higher energy products and enables the magnets to achieve more complicated design features.

Ceramic or Ferrite

Comprised of sintered iron oxide and barium or strontium carbonate, ceramic (or ferrite) magnets are typically inexpensive and easily produced, either through sintering or pressing. However, because these magnets tend to be brittle, they require grinding using a diamond wheel. They are one of the most commonly used types of magnet, and are strong and is not easy to demagnetize.

Applications

Within the industrial sector, magnets are often used as magnetic sweepers, sorters, and to separate impure metals during metal manufacturing or recycling. In electronic applications, magnets are used in speakers, televisions, telephones, radios, and videotapes. Typically, electromagnets are used within televisions, computers, and telephones because of their extreme strength. For this same reason, they are also used in on-off applications, such as cranes sued for heavy lifting.

Permanent magnets are perhaps the most common type—they are used to manufacture refrigerator magnets, as well as in jewellery making. Temporary magnets can be useful in applications that generate a temporary magnetic field and require a magnetic response for the duration of the field.