Question

Draw the graph for variation of magnetic suceptibility (`chi`) of a material with temperature (T) and hence explain Curie temperature. 

Answer 1

• Ferromagnetism depends upon temperature.
• As the temperature of a ferromagnetic material is increased, the domain structure starts distorting because the exchange coupling between neighbouring moments weakens.
• At a certain temperature, depending upon the material, the domain structure collapses totally and the material behaves like paramagnetic material.
• The temperature at which a ferromagnetic material transforms into a paramagnetic substance is called Curie temperature (T_c) of that material.
• The relation between the magnetic susceptibility of a material when it has acquired paramagnetic property and the temperature T is given by
  `chi=C/(T-T_c)` for T > T_c where C is a constant.