Why Are Neodymium Magnets So Strong?

Neodymium magnets are known for their exceptional strength. Keeping one of these near your credit cards or cassette tape collection would certainly be a bad idea--data loss would be almost completely assured. Those uninitiated with magnetic force and what causes it may not realize what gives these magnets their awesome power. This is somewhat simple to grasp if you can take in a few key concepts.

Before you can understand why neodymium magnets are so powerful, you need to understand how magnets work. A good starting point is understanding an electromagnet, which is magnetic because of the flow of electricity through a given current. In fact, any current--even the wires going through the walls of your house--has a magnetic current. This is because the movement of electrons creates a directional magnetic field capable of attracting other electrons.

Other Magnets
Magnets only attract certain metals, such as iron, nickel and cobalt. These metals all have an unpaired electron in their outer orbits, which tends to align with magnetic fields. Spread throughout an entire chunk of metal, it is these unpaired electrons that pull the metal toward a given magnet. Temporary magnets can be formed anytime one of these metals is exposed to magnetic force for a long period of time, as this will temporarily align the electron spin in a given direction. Permanent magnets are magnets that, for whatever reason, are permanently shaped in such a way that directs electron spin in a given direction. A prime of example of this is, of course, the neodymium magnet.

Neodymium Magnets
Neodymium may the rare earth metal neodymium magnets are named for, but the magnets themselves are actually an alloy of iron, boron and neodymium. The magnet's chemical composition is typically Nd2Fe14B, a composition that forms a tetragonal crystal structure. This structure has what is called exceptionally high uniaxial magnetocrystalline anisotropy--as high as HA~7 Tesla. In layman's terms, this means neodymium magnets' atoms are arranged in such a way as that the electron spin is permanently and very strongly aligned in a given direction, giving the compound the extreme magnetic force for which it's famous.

Cost
Neodymium magnets were discovered in 1982 by three groups at once: Sumitomo Special Metals, General Motors Corporation and The China Academy of Sciences. It found widespread uses quickly because of its relative cheapness compared to samarium cobalt, the rare earth magnet commonly used before the discovery of neodymium magnets. Neodymium being the third-most common rare earth metal on the planet means it is much cheaper than samarium.

Example Uses
Neodymium magnets are all around us. Odds are the hard drive in the computer you're reading this on features one, as do the speakers by your computer. Hospitals use these magnets in their MRI machines, and they're also used in many security systems. Because of their extreme power, neodymium magnets are also popular with magnet enthusiasts.

Tags: neodymium magnets Neodymium Magnets,Strong Smco magnets