The term “rare earth magnets” is a bit of a misnomer. The 17 elements that comprise this group are actually quite abundant, though they are scattered over vast lands so gathering them tend to be costly. When combined, the resulting metals exhibit incredible magnetic properties. They can generate an attractive force thrice as strong as traditional magnets made of ceramic and alnico.
The development of neodymium magnets got underway in the 1980s. Mixing neodymium with iron and boron produced the NIB magnets named after their initials. While effective, their susceptibility to oxidation meant they had to be covered with epoxy resin or metals like nickel and zinc which are not corrosive. Their effectiveness drops down starting at 212°F.
Their prices have since decreased which has spurred demand in various types of businesses. NIB magnets are now used in household products (flashlights, speakers) and industrial machinery (planes, wind turbines). They can even be found in children’s toys.
Although NIBs are cheap and powerful, they are no match for samarium-cobalt magnets. The latter, developed in the 1960s, produces an even stronger magnetic field and they are not prone to corrosion. It can also operate at far greater temperatures making them ideal for heavy industrial applications. On the downside, they are very brittle and expensive to produce.
Rare earth magnets can be compared through their properties such as remanence, Curie temperature, coercivity, and energy product. Remanence is just another term for their strength. The Curie temperature is the point at which their magnetism decreases. Coercity, meanwhile, is their resistance to being demagnetized. Finally, their energy product is the measure of their energy density output.