20x4 mm Neodymium Magnets Disc Super Large Strong Round Magnet. Description: Neodymium is an element that was discovered in 1885 (pronounced "nee-eh-dim-ee-em"), it was not until the early 1980's that the element was alloyed with iron and boron to create the "Neodymium Magnets" that we use today. The name "Rare Earth Magnets" does not refer to their abundance.
Neodymium is about as common as tin or lead. The term Rare Earth relates to a specific group of elements in the Periodic Table which lists all known elements in groups according to their similar chemical properties. There are two types of "Rare Earth Magnets" SMCO (Samarium-Cobalt) and Neodymium. Neodymium are the magnetically stronger and cheaper of the two but are more susceptible to oxidation, this is why they are protected by Nickel plating. Neodymium magnets are many times more powerful than the better known Ferrite magnets.The magnetic strength of a Neodymium magnet is measured by its "N" number; the higher the number the more powerful the magnet. N numbers range from N27 - N52. It is also important to note that the higher powered magnets are also very brittle. The power of the attraction of a magnet also is related to the thickness of the Steel to which it is being attracted. The thicker the steel the stronger the magnetic attraction! 20mm diameter x 4mm thickness. Return posting costs will be at your expense unless it is due to a mistake on our end.
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