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Q & A: magnets: physics and fakes

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Most recent answer: 10/22/2007
Q:
Could you please tell me what the difference between tectonic, ceramic, metallic, hematite and plastic magnets is? And besides.. What are your average magnets made out of?
Thanks!
- Spencer (age 17)
Texas
A:
Metallic magnets are made of metals, materials which have freely moving conduction electrons that donít freeze out when the material is cooled. Typical metallic magnetic materials are alloys of iron, cobalt, nickel, or neodymium.
Hematite is a particular non-metallic iron oxide which also forms a weak magnet.
Ceramics are materials with many small crystals pressed together with non-crystalline regions binding them together. Ceramics of magnetic crystals often make good permanent magnets, because the unevenness of the material helps keep the magnetic domain walls (between regions where the magnetism points different directions) from moving around, which would demagnetize the material.
I donít know of any plastics which form practically useful magnets, although maybe there are some. More likely a íplastic magnetí is made of plastic with little pieces of some other magnetic material imbedded in it.
The only thing I could find on ítectonicí magnets was that name is used as a brand name by some oufit thatís been cited by the Texas Attorney General for making unsupported health claims. As a Texan, you might contact that office to see where that stands legally.

Most ordinary magnets are made of iron alloys.

Mike W.

(published on 10/22/2007)

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