Rare Earth Plate Magnets

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You can make plate magnets from two combinations of rare earths. These elements have come to replace all the previous materials used to make these types of magnets. Rare earth magnets are superior in nearly all respects when compared to magnets made from iron or alloys that incorporate iron. These newer magnets were only invented in the 1960’s. 
 
When these materials are used to make plate magnets, they create very powerful devices for removing metal fragments from moving conveyors, chutes and ducts. In this age when high precision and accuracy are regarded as necessities in nearly all industrial applications, these sorts of magnets are vital to the successful manufacturing. When samarium cobalt was finally developed into suitable forms to make plate magnets, manufacturers were thrilled by this new material’s superiority over the magnets previously used.
 
Samarium-cobalt is sometimes alloyed with iron, copper and zirconium to give it different magnetic qualities and also to affect its general durability. When produced as an alloy with these multiple metals, samarium cobalt plate magnets significantly outperform those made ferrite and alnico in two key areas. This type of magnet has a much higher coercivity rating. This means that the magnets made from these metals do not lose their magnetism nearly as easily as others. Furthermore, samarium cobalt magnets produce a very dense magnetic field. The density of this field can be three times as great as that of an alnico magnet.
 
The cost of these magnets was very high. Researchers began to look for less expensive magnets that would have similar or greater power. They looked again to the rare earths that had helped produce the samarium cobalt variety. Neodymium magnets held great promise. They were similar or superior in strength to most other magnets and were cheaper than those made from samarium cobalt. However, these new magnets had one key deficiency. They suffered from very low Curie temperatures. This meant that they began to lose magnetism at high temperatures. Since many industrial applications require exposure to high temperatures, this made neodymium problematic. 
 
The problem was solved when developers toyed with the mixture of elements in the neodymium alloy. Originally, the alloy contained neodymium, iron and boron. In order to improve resistance to heat, researchers added small amounts of other rare earths. This still did not give the alloy an equal Curie temperature when compared to alnico magnets or those made from samarium cobalt. However, its superiority in other areas and its inexpensive costs made it worth accepting that drawback.
 
Even with the arrival of inexpensive neodymium on the market, there is still a place for samarium-cobalt plate magnets. Their high Curie temperature makes them necessary in the hottest applications. The older types of magnets now find their primary uses in certain products.
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April Gilbertson has 12 articles online

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Rare Earth Plate Magnets

This article was published on 2012/01/17