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More magnetism

  1. Mar 27, 2004 #1
    why can certain metals be magnetised but others like copper cannot?
    what what is the difference between permanent magnet and temporary magnets?
     
  2. jcsd
  3. Mar 28, 2004 #2

    turin

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    It has to do with interatomic coupling. I think (not absolutely positive) that all materials have what is called a Curie Temperature. Above this temperature, the ferromagnetism changes to paramagnetism, and the material cannot hold the magnetism without the applied field. Fe, Co, and Ni all have Curie temperatures much higher than room temperature. The higher the temperature, the more thermal vibrations break the interatomic coupling, and destroy the domains in the material.

    I was once told that it has something to do with the d-orbitals, but that never made very much sense to me.
     
  4. Apr 1, 2004 #3
    wads ferromagnetism and paramgnetism and as well as bimagnetism???
     
  5. Apr 1, 2004 #4

    turin

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    Ferromagnetism is the characteristic of responding to an applied magnetic field by the allignment of interatomic domains that remain alligned after the applied field is removed.

    The coupling of the domains (this is the part that I don't quite understand: how/why they are coupled) is stronger than the intermitant jolts that the atoms receive from thermal vibration. The higher the temperature, the stronger the thermal vibrations, so the ferromagnetism of a material is temperature dependent. Also note that, since thermal vibrations are statistical, there are always a few here and there that are strong enough to jolt the domains apart. The domains quite often recombine and reallign due to the presence of the field from the other domains. However, after a sufficiently long time, the magnetism eventually decays.




    Paramagnetism is the characteristic of responding to an applied magnetic field by the allignment of the magnetic moments of the electrons themselves (not orbital, but spin) and the allignment of the magnetic moments of the protons (maybe quarks, not sure).

    All materials exhibit paramagnetism. This causes a slight attraction by virtue of the minimization of the configuration energy due to the allignment. The attraction is nowhere near as pronounced as in the case of ferromagnetism.




    I'll assume that you mean "diamagnetism," because I've never heard of bimagnetism.

    Diamagnetism is the characteristic of responding to an applied magnetic field by the induced precession of the electron orbitals.

    I'm not sure if all materials exhibit this property. This actually cases materials to be repelled by a magnetic field (to be more precise, paramagnetism and ferromagnetism motivate materials in the direction of the gradient of the magnetic field whereas diamagnetism motivates materials in the opposite direction as the gradient. Strictly speaking, a magnetic field does not cause the influence on a material, the gradient does.) This property can cause (has been shown to accurately predict) levitation.
     
    Last edited: Apr 1, 2004
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