Magnets can be classified into two main categories, permanent and non-permanent magnets. Permanent magnets are objects that, once magnetised, can retain their magnetism whilst non-permanent (temporary) magnets require an external magnetic or electrical field to magnetise. Non-permanent magnets lose their magnetism once the external field is removed (i.e. electromagnet).
Permanent magnets contain material that is ferromagnetic and can be categorised in the following material groups:
1. Ferrite or Ceramic Ferrite (Fe)
2. AlNiCo (Aluminium, Nickel and Cobalt)
3. Samarium Cobalt (SmCo)
4. Neodymium (NdFeB or NIB)
Flexible and bonded magnets can use the above materials and are lower in cost and strength.
Permanent magnets can be further divided into rare earth and non-rare earth types.
• NdFeB and SmCo are the most common rare earth magnets from the Lanthanide series on the periodic table.
• Ceramic/Ferrite and AlNiCo magnets are non-rare earth magnets.
The following graphs show the relative difference between cost, magnetic strength and temperature grades. For specific information see the magnet tables.
