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Diamagnetism




Diamagnetism


  • Diamagnetic effects occurs in materials where magnetic field due to electronic motions i.e orbiting and spinning completely cancels each other
  • Thus for diamagnetic materials intrinsic magnetic moments of all the atoms is zero and such materials are weakly affected by the magnetic field

  • The diamagnetic effects in material is a result of inductive action of the externally applied field on the molecular currents
  • To explain the occurrence of this effect ,we first consider the Lenz law accordingly to which, whenever there is a change in a flux in a circuit, an induced current is setup to oppose the change in flux linked by the circuit
  • Here the circuit under consideration is orbiting electrons in an atom, ions or molecules constituting the material under consideration
  • we know that moving electron are equivalent to current and when there is a current ,there is a flux
  • On application of external field ,the current changes to oppose the change in flux and this appear as a change in the frequency of the revolution
  • The change in frequency gives rise to magnetization as a result of which each atom will get additional magnetic moment ,aligned opposite to the external field causing it
  • it is this additional magnetic moment which gives diamagnetic susceptibility a negative sign which is order of 10-5 for most diamagnetic material (e g. bismith,lead,copper,silicon,diamond etc)

  • All substances are diamagnetic ,although diamagnetism may vary frequently be masked by a stronger positive paramagnetic effect on the part of external magnetic field and as a result of internal interactions
  • Diamagnetic susceptibility is independent of temperature as effect of thermal motion is very less on electron orbits as long as it deform them




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