Neodymium magnets, invented in the 1980s, are the strongest and most affordable type of rare-earth magnet. Neodymium alloy (Nd2Fe14B) is made of neodymium, iron and boron. Neodymium magnets are typically used in most computer hard drives and a variety of audio speakers. They have the highest magnetic field strength, but are inferior to samarium-cobalt in resistance to oxidation and Curie temperature. Use of protective surface treatments such as gold, nickel, zinc and tin plating and epoxy resin coating can provide corrosion protection where required.
Traditionally, the high cost of these magnets has limited their use to applications requiring compactness together with high field strength. Both raw materials and patent licenses were expensive. Beginning in the 1990s, NIB magnets have become steadily less expensive and more popular in other applications such as children's magnetic building toys.