Cold and Magnets
Does cold have an effect on magnetism?
Yes. temperature [which I think you mean by "cold"] can have a profound
effect on magnetism. Many permanent magnets will permanently lose their
magnetism if heated above certain temperature. Other materials turn on and
off magnetism, depending upon the temperature.
At extremely low temperatures, say less than 4 Kelvin, where much of the
thermal agitation of atoms and molecules of a material has disappeared,
magnetism is a very important phenomenon.
Cold can have an effect on magnetism, because cold can have an effect of how
fast charged particles move. It is the motion of charged particles, usually
electrons around a nucleus, that produces magnetic fields. Cooling a metal
can make the motion within less random, thus allowing more atoms to line up
with each other. This increases the magnetic field of the material. On the
other hand, making a magnet very hot will cause more random motion,
resulting in less allignment of molecules and less megnetism.
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Update: June 2012