Classification of magnetic material

Classification of magnetic material

(A) Phenomenological classification

  • Such type of classification is based on sign and magnitude of magnetic susceptibility χ
  • According to this type of classification there are three type of magnetic material
    (i) Diamagnetic materials -> χ < 0
    i.e magnetic susceptibility is negative
    (ii) Paramagnetic material -> χ > 0
    i.e magnetic susceptibility is positive and less then unity
    iii) Ferromagnetic material -> χ>> 0
    i.e magnetic susceptibility is positive and is very high
  • This approach ignores the nature of microscopic carriers of magnetism and does not consider their interaction
  • Through this approach magnetic states like anti-ferromagnetic ,ferromagnetic cannot be recognized

(B) Main Effects of external Field

  • Main effects related to the actions of external field on magnetic moments of atomic carriers are
    (i) Diamagnetic effects
    (ii) Paramagnetic effects
  • It was first proposed by the Ampere that the magnetic properties of a material arises due to large number of tiny current loops within the material
  • These tiny microscopic current loops are associated with the motion of electrons within the atoms and each current loop has a magnetic moment associated with it
  • In addition to the orbital motion of electron around the nucleus electron also spin or rotate about their own axis
  • Thus internal magnetic field in a material is produced by electron orbiting around the nucleus and by the spin of the electrons as shown below in the figure .This is how internal magnetism is produced in the material

    Diamagnetic effects and  paramagnetic effect