An MRI machine, which uses supermagnets.
A “supermagnet” is often jargon for neodymium magnets, the most powerful permanent magnets known. It can also be a term for a powerful electromagnet, like the one used in hospitals for functional magnetic resonance imaging (fMRI). Both of these magnets are much stronger than typical ferrite bar magnets and can be a health hazard to anyone using a pacemaker. Neodymium magnets are also so strong that someone could be injured just playing with large samples of them – the force they generate when they are put together can be strong enough to pierce human skin. The cost of neodymium magnets is around $44 (US dollars) per kilogram ($97 per pound).
Bar magnets are considerably weaker than super magnets.
The best known and most widespread form of supermagnet are neodymium magnets, made from an alloy of neodymium, iron, and boron, Nd 2 Fe 14 B. They only became widely available in the 1990s. Unlike ferrite magnets, which they are a dull gray, a The super neodymium magnet is shiny and silvery, like polished stainless steel. Neodymium magnets can hold 1,300 times their own weight, a strength-to-weight ratio similar to that of the strongest animals, such as the tropical mite Archegozetes longisetosus. This means that a one gram neodymium supermagnet can hold a 1.3 kg (2.8 lb) sphere of iron.
Neodymium magnets are the strongest on Earth.
Neodymium magnets have a variety of uses, the most common being for stabilization and angled head motors in computer hard drives. Magnets are also popular with hobbyists, who use them to build unique structures that are held together entirely by tiny magnets. Neodymium magnets are also popular with science teachers, who use them to demonstrate Lenz’s Law, the phenomenon whereby strong magnets exhibit magnetic breakdown when brought near conductive non-ferrous metals. This can be demonstrated by dropping a neodymium magnet through a copper tube. The magnet will fall incredibly slowly as it travels down the pipe.
Neodymium magnets must be used with care. If ingested, they can compress the intestine, causing gastrointestinal perforation, which can lead to death if surgery is not performed immediately. As mentioned above, neodymium magnets are dangerous for people with pacemakers. In addition to health, neodymium magnets can be dangerous for data: these magnets are one of the few materials that can erase credit cards and saturate hard drive data so intensely that it becomes unrecoverable, even using the better techniques. Large neodymium magnets tend to attract each other or ferrous objects so strongly that they break apart, sending magnetic shrapnel in all directions. Large neodymium magnets must be handled with care.