Guide to Magnet Materials

The composition of magnets and the source of their magnetism must be considered in order to classify them. Magnets that retain their magnetism after they have been magnetised are called permanent magnets. Temporary magnets are magnets that perform like permanent ones when in close proximity to a magnetic field, but rapidly lose that effect when removed. An Electromagnet is a wire coil that acts as a magnet upon receiving electrical current. The magnet's strength can also be altered by adjusting the strength and direction of the current.

The types of magnets available are listed below.

Permanent Magnets - Permanent magnets generally fall into four categories: neodymium iron boron (NdFeB), samarium cobalt (SmCo), alnico, or ceramic.

• Neodymium Iron Boron (NdFeB) - It is commonly known as Neodymium, Iron, Boron or Neo Magnets, which are rare-earth magnets created by alloying neodymium, iron, and boron. The first ones were invented in 1982 by General Motors and Sumitomo Special Metals. Neodymium magnets are currently the strongest permanent magnets available.
• Samarium Cobalt (SmCo) - It is also known as Rare Earth cobalt, RE cobalt, RECo and CoSm.  They do not have as much strength as the Neodymium magnets (NdFeB), but they have three major advantages. Magnets made from SmCo can operate over a wider temperature range, have high temperature coefficients and are much more corrosion resistant.
• Alnico - All three main ingredients of Alnico magnets -- aluminum, nickel, and cobalt -- are represented by the first two letters of their names. Although they are temperature-resistant, they can easily become demagnetized. They are often replaced by ceramic and rare earth magnets in certain applications. Magnets can be made by either sintering or casting, and each process produces different magnet properties. Mechanical properties are enhanced by sintering. With casting, magnets can be designed with more complicated features and are able to achieve higher energies.
• Ceramic or Ferrite - Ceramic or ferrite permanent magnets are typically made from sintered iron oxide and barium or strontium carbonate and are inexpensive and easy to produce, either by sintering or pressing. This is one of the most commonly used types of magnet. They are strong and can be easily demagnetised.

Electromagnets - The creation of an electromagnet is made by winding a wire into loops around a core material. This is also known as a solenoid. By passing electricity through a solenoid, a magnetic field is created for magnetising electromagnets. The strongest field occurs at the inside of the coil, and the intensity of the field increases with the number of loops and the current strength.

You can also learn more about magnets and other metal materials by checking our free guide 'A quick guide to magnets, magnetic metals and non magnetic metals'