Curie   temperature      For   a   ferromagnetic  substance  the variation of susceptibility, c with temperature, above the ferromagnetic Curie temperature, Q is given by,

c = C/(T- Q )

where  C  is  the Curie constant, and T the absolute temperature. Q is called   the Curie   temperature.   When   T  approaches Q the susceptibility  goes  to infinity. This means that the substance possesses  spontaneous magnetization even without the presence of external   magnetic  field.  Above  the  Curie temperature  the substance behaves like paramagnetic material.