To fully understand rare earth magnets, it is important to understand what they are made of and where they come from. There are 17 elements in the periodic table included in the rare earth family, the fifteen elements known as lanthanides plus scandium and yttrium. These seeds of technology have each played their part in the ceaseless development of hi-tech industries. You might be surprised to know there are no fewer than eight of the 17 elements in your iPhone including neodymium, dysprosium and praseodymium all of which are used in the alloys used to create rare earth magnets along with the element samarium.
Rare earth magnets are the strongest permanent magnets available and have significantly higher performance than ferrite (ceramic) and alnico magnets. The term ‘rare earth’ can be misleading as rare earth metals are relatively abundant in the Earth’s crust. However, they are rarely found in their concentrated form, rather they are typically dispersed with other elements.
There are two types of rare earth magnet, neodymium magnets (NdFeb) and samarium cobalt (SmCo) magnets. There are many different grades of each, all of which have different properties.
Samarium cobalt magnets were the first to be discovered in 1966 by Dr. Karl J. Strnat and are made from an alloy of samarium, cobalt, iron, copper, hafnium, zirconium and praseodymium. Until the introduction of neodymium magnets they were the strongest magnets available, they are extremely difficult to demagnetise, have high maximum operating temperatures and have a high resistance to corrosion.
When neodymium magnets were discovered in 1982 by General Motors and Sumitomo Special Metals they took the title of the strongest permanent magnets available, which they retain to this day. Neodymium magnets are made from an alloy that mainly consists of neodymium, iron and boron and, depending on the grade of magnet being produced, varying amounts of dysprosium and praseodymium. Regular grades of neodymium have lower maximum operating temperatures than samarium cobalt magnets and are susceptible to corrosion if not coated.
Rare earth magnets are used when space is at a premium or the greatest possible magnetic pull is required. While they are vital for many technology, manufacturing and engineering industries they are equally as popular for hobbies, crafts and DIY due to their performance and affordability.
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