These magnets, as stated earlier, are stronger (almost fifteen times stronger) than ferrite or alnico magnets. These rare-earth magnets are so strong that they can lift up to four hundred times their own weight. They are used in expensive electronic gadgets such as cell phones, computer hard drives and the like; and since they are expensive, to save them from chipping and breaking, these magnets are coated with nickel. This nickel coating also protects them from rust and stains, and gives them a shiny appearance.
These magnets can be distinguished into two broad categories which are as follows:
- Neodymium (Nd-Fe-B) magnets - Neodymium magnets consist of neodymium, iron, and boron. These magnets are the strongest and most affordable of the lot. These are the magnets that are used in computer hard drives and speakers as they have the strongest magnetic field. These magnets are expensive as the cost of raw materials required is quite high and also because of the cost of the licensing of the patents. These magnets are also not very resistant to oxidation and temperature, thus they have to be coated with nickel or gold. Neodymium magnets are also corrosive but the main advantage is that they have a high-energy output for their size. These magnets can be used in microphones, computer printers, and speakers as well.
- Samarium-cobalt (Sm Co) magnets - Samarium cobalt magnets consist of samarium, cobalt, and iron. These magnets are not as commonly available as neodymium magnets since the latter type is easy to produce. Samarium Cobalt magnets are resistant to demagnetization and also stable under high temperature unlike Neodymium magnets. These magnets are also resistant to oxidation but shaped magnets are prone to breaking and chipping when exposed to thermal shocks. These magnets can be used in satellite systems and traveling wave tubes.