Neodymium Magnet | Universe Today

Written by Jerry Coffey

Neodymium magnets are a type of rare Earth magnet that is manufactured using a compound of neodymium, iron, and boron. It is currently the strongest permanent magnet available. The tetragonal structure has exceptionally high uniaxial magnetocrystalline anisotropy. This gives the compound the potential to have high resistance to being demagnetized. The compound also has a high saturation magnetization. Therefore, as the maximum energy density is proportional, this magnetic phase has the potential for storing large amounts of magnetic energy, considerably more than samarium cobalt (SmCo) magnets, which were the first type of rare earth magnet to be commercialized. In practice, the magnetic properties of Neodymium magnets depend on the alloy composition, microstructure, and manufacturing technique employed.

In 1982 General motors and a couple of other companies worked together to discover the compound that neodymium magnets are made out of. They were mainly looking for a way to cut the costs associated with the SmCo magnets. There are two ways to produce these magnets: the classical powder metallurgy or sintered magnet process and the rapid solidification or bonded magnet process. Sintered Neo magnets are prepared by pulverizing an ingot precursor and liquid phase sintering the magnetically aligned powder into dense blocks which are then heat treated, cut to shape, surface treated and magnetized. Currently, between 45,000 and 50,000 tons of sintered neodymium magnets are produced each year, mainly from China and Japan.

Bonded Neo magnets are prepared by melt spinning a thin ribbon of the Nd-Fe-B alloy. The ribbon contains randomly oriented nano-scale grains. This ribbon is then pulverized into particles, mixed with a polymer and either compression or injection molded into bonded magnets. Bonded magnets offer less flux than sintered magnets but can be net-shape formed into intricately shaped parts and do not suffer significant eddy current losses. There are approximately 5,500 tons of Neo bonded magnets produced each year. In addition, it is possible to hot press the melt spun nanocrystalline particles into fully dense isotropic magnets, and then upset-forged/back-extruded these into high energy anisotropic magnets

Neodymium magnets are the cutting edge of magnet technology that is in every day use. They are in many of the items that you see or hear about every day. Computer hard disk drives, voice coil motors, MRI's, guitar pick-ups, and servo motors are just a few of the normal uses. There is a nice article here on all of the uses of neodymium magnets.

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