Curie’s law

The susceptibility (X) of a paramagnetic substance is propor­tional to the thermodynamic temper­ature (T), i.e. x = C/T, where C is the Curie constant. A modification of this law, the Curie-Weiss law, is more generally applicable. It states that  X = C/(T- θ), where θ is the Weiss constant, a characteristic of the ma­terial. The law was first proposed by Pierre Curie and modified by an­other French physicist, Pierre-Ernest Weiss (1865-1940).