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Neodymium magnet

From Academic Kids

Rare-earth magnet redirects here. For another type of rare-earth magnet that is less commonly used, see Samarium-cobalt magnet.
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Neodymium magnet on a bracket from a hard drive

A neodymium magnet (also, but less specifically, called a rare-earth magnet) is a powerful magnet made of a combination of neodymium, iron, and boron — Nd2Fe14B. These magnets are very strong in comparison to their mass, but are also mechanically fragile and lose their magnetism at temperatures above 80 degrees C. They have replaced marginally weaker and significantly more heat-resistant Samarium-Cobalt magnets in most applications, due mainly to their lower cost.

Used for stabilization and angular head motors in computer hard drives, Nd2Fe14B magnets are also popular with hobbyists, and a small magnet can have amazing properties — it exhibits magnetic braking when moved near a non-magnetic metal due to induced eddy current, and a somewhat larger magnet interacts strongly enough with the magnetic field of the Earth to allow its tendency to align with that field to be perceived directly when holding it, essentially forming a compass. Also, even a small neodymium magnet is powerful enough to destroy the contents of a floppy disc to such an extent that the information is unrecoverable, a guarantee not present with techniques such as formatting the disk. NdFeB magnets are often strong enough to not only magnetize color CRT shadow masks, but also physically deform the mask itself. Such damage is typically irreparable.

Caution

Neodymium magnets should be handled with caution. Magnets that are slightly larger than the size of a penny are powerful enought to lift over 10 kilos. [1] (http://www.gaussboys.com/product_info.php?products_id=22) They are hazardous, being able to pinch skin or fingers when suddenly attracted to a magnetic object. Because they are made with special powders and coatings, the magnets are very fragile and break at temperatures of over 300 degrees Fahrenheit, or when they manage to escape your grip and smash together. When they break, the magnets may break so suddenly that flying pieces may cause eye injury. Large-sized neodymium magnets are not toys and should be kept out of reach of small children. Neodymium magnets should also be stored away from electrical appliances, magnetic (bank)cards and computer monitors, as damage may be irreparable.

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