Alnico

From Wikipedia, the free encyclopedia
Jump to: navigation, search

Alnico is an acronym[1] (A short form or an abbreviation formed from the starting letters of other words and spoken as a word) of iron alloys which are made up of iron and aluminium (Al), nickel (Ni) and cobalt (Co), and hence the acronym Al-Ni-Co. Alnico may also contain copper and sometimes titanium.

Alnico alloys are ferromagnetic (a mechanism by which some materials form permanent magnets). Alnico alloys also have a high coercivity (they do not easily lose their magnetism) and are used to make permanent magnets. Before, rare earth magnets were developed in the 1970s, alnico magnets were the most strongest type of magnet. The development of Alnico began when T Mishima in Japan found that an alloy of iron, nickel, and aluminium had double the coercivity than best magnets of that time. (the coercivity of Alnico is 400 oersted)[2].

Properties[change | change source]

Alnico alloys make strong powerful magnets, and can be made magnets (called magnetising) to produce strong magnetic fields. Rare-earth magnets like neodymium and samarium-cobalt are the only easily found magnets which are stronger than alnico magnets. Alnico magnets produce very strong magnetic fields at their poles (a pole is one of the two ends of a magnet) as high as 1500 gauss (0.15 tesla which is about 3000 times stronger than earth's magnetic field.

Some types of alnico magnets are isotropic (properties are same in all directions) and can be properly magnetised in all directions. Other types like alnico 5 and alnico 8 are anisotropic (properties change when direction changes) have a preferred direction (one direction would be better than other directions) for magnetisation. Anisotropic alnico alloys will make stronger magnets in their preferred direction than an isotropic alnico alloy.

Alnico magnets have one of the highest temperatures (around 800 °C (1,470 °F)).[3] They are the only magnets that have useful magnetism even when heated red-hot.[4]

In 2008, the cost of Alnico magnets was about $44/kg ($20/pound).[5]

References[change | change source]

  1. Hellweg, Paul (1986). The Insomniac's Dictionary. Facts On File Publications. pp. 115. ISBN 0-8160-1364-0.
  2. Cullity, B. D.; C. D. Graham (2008). Introduction to Magnetic Materials. Wiley-IEEE. pp. 485. ISBN 0471477419. http://books.google.com/books?id=ixAe4qIGEmwC&pg=PA485.
  3. Arnold-Alnico Magnets
  4. Hubert, Alex; Rudolf Schäfer (1998). Magnetic domains: the analysis of magnetic microstructures. Springer. pp. 557. ISBN 3540641084. http://books.google.com/books?id=pBE42lLYs-MC&pg=PA557.
  5. Frequently Asked Questions