Neodymium Magnets

Neodymium magnet, also called as Neo magnet, is an alloy of neodymium, iron and boron and its chemical representation is given as Nd₂Fe₁₄B. Neodymium magnets are called as rare-earth magnets because the major element of these magnets, Neodymium, falls in the lanthanide series of the periodic table. The chemical elements of the lanthanide series are rare on Earth. Though, neodymium is present in the lanthanide series it is not that rare and is quite common in the Earth's crust.

History of Neodymium Magnets

Neodymium (atomic weight 60) was discovered by an Austrian scientist named Baron Carl Auer von Welsbach, in 1885. The neodymium magnet compound was simultaneously formulated by Sumitomo Special Metals, General Motors Corporation, and The China Academy of Sciences, in 1982. The cost of the permanent magnet, Samarium Cobalt (SmCo), that was developed earlier was too high, and there was a need to find an economic magnet, which lead to the discovery of neodymium magnet. The manufacturing technique of all the three companies differed from each other. General Motors manufactured neodymium magnets in powder bonded form, while Sumitomo manufactured them in sintered form.

Properties of Neodymium Magnets

Neodymium magnets are very strong, when compared to their size. A neodymium magnet can sustain weight of a substance 1,300 times its weight. Neodymium magnets are corrosive and brittle in nature, thus they are always coated. The strength of neodymium magnets is in the range N24-N55, N55 being the strongest. The crystal structure of Nd₂Fe₁₄B, is tetragonal in shape. Before knowing the magnetic properties of Neodymium magnets, let us take a look at the terms related to magnetism:

Curie Temperature: It is the temperature beyond which the magnet loses its magnetic properties.
Coercivity: It is the intensity of the magnetic field to demagnetize the magnet, i.e. the energy of a magnetic field applied that makes the magnet to lose its magnetic properties. It can also be called as resistance of a magnet to demagnetization. Higher the coercivity, the stronger is the magnet.
Remanence: It is the magnetic effect, left by the magnet in a medium, after the magnet is removed.

The table given below gives brief information on the magnetic properties of bonded and sintered neodymium magnets:

Magnetic Property	Unit	Sintered Neodymium Magnet	Bonded Neodymium Magnet
Curie Temperature (Tc)	Degree Celsius	310-400	310-400
Coercivity (Hc)	kilo Ampere/Meter (Oersted)	750-2000	600-1200
Remanence (Br)	Tesla	1-1.4	0.6-0.7

Application of Neodymium Magnets

Neodymium magnets have a wide application in upcoming technologies, due to their economic cost and useful magnetic properties. Music systems, automobiles, computer hardware are some of the fields that make use of neodymium magnets. The following list gives a brief idea about the applications of neodymium magnets:

• Security systems
• Speakers of music system
• Computer hard drives
• Magnetic Resonance Imaging (MRI)
• Household purposes (to hold metallic things)
• Toys
• Magnetic therapy for diseases, like arthritis

Hazards due to Neodymium Magnets

Neodymium magnets being the strongest permanent magnets need to be handled carefully, while using them. The magnets are so strong that two neodymium magnets of opposite polarity can break into parts, while attracting each other. They should be always kept away from small children because children have a habit of swallowing things, and if they swallow two neodymium magnets of opposite polarity; the magnets can cause serious injury to the inner body organs, like the esophagus. Sudden attraction of a large neodymium magnet to a metallic object can cause serious injury, like breaking bones, if your hand is in the way. Data in the floppy disc can get erased, if it comes in direct contact with a neodymium magnet. The magnetic stripes on credit cards that have information, can get erased because of these magnets. Neodymium magnets should be kept away from electronic devices, like televisions and computer monitors. Pacemakers do not function properly in the presence of a magnet, thus a person who is using a pacemaker should not come into contact with neodymium magnets.