A COMPARISON OF MAGNETIC MATERIALS – AT A GLANCE

There are five types of magnet material that a magnet can be manufactured from:

1 - Neodymium iron boron (NdFeb)

Neodymium magnets are the most powerful magnets available (per unit volume) with the ability to attract 1,000 times their own weight. They have an elaborate manufacturing process of vacuum melting, milling, pressing and sintering.

These magnets can then sliced into smaller magnets or ground to tighter tolerances using diamond grinding tools. All neodymium magnets are plated to prevent rusting and are used wherever a very small size and maximum power is needed.

2 - Alnico

Alnico is cast in a foundry. Patterns are used to make sand moulds and molten magnet material is poured into sand moulds. The patterns, tooling and high cost of Cobalt can make alnico magnets expensive. Alnico can also be manufactured using a sintering process to form smaller and more accurate magnets than those that are formed using a casting technique.

3 - Ferrite (Fe3O4)

Ferrite is manufactured using powder sintering technology and is sintered using exact size tooling into a range of industry standard sized discs, rings and block shapes. An industry sized block is a 150mm x 100mm x 25mm.

These blocks can then sliced into smaller magnets or ground to tighter tolerances. Ferrites are used extensively in loudspeakers and security systems industries.

4 - Samarium cobalt (SmCo)

Samarium Cobalt is manufactured using vacuum powder sintering technology and is sintered using special tooling techniques into standard disc, ring and block shapes.

These magnets can then be sliced into smaller magnets or ground to tighter tolerances using diamond grinding tools. Samarium cobalt is not as powerful as neodymium but it is still a rare earth high-power material. It offers a high performance per unit volume and is used in high-power applications where long term reliability is critical.

5 - Magnetic rubber

Magnetic rubber is produced by heavily loading ferrite powder of barium or strontium base into a synthetic rubber or PVC matrix and either extruding to shape or calendaring into thin sheets. Magnetic rubber can be cut with scissors and can be supplied with adhesive backing, bright coloured vinyl facing and is easily cut into special shapes using form cutters.

Each magnet material has many grades and variations to provide a variety of slightly different magnetic properties. More details about different grades of each type of magnet can be found in the relevant section of our Tech Centre.

The following details give a simple overview of the five Magnet Materials:

• Br = Volume of magnetism
• Hc = Resistance to demagnetisation
• BHmax = Maximum energy product
• Temperature coefficient = Percentage of magnetism lost for each degree Celsius rise in temperature but regained on cooling