A law that describes the magnetic susceptibility (X) of a ferromagnet (see ferromagnetism) at temperatures above the Curie temperature. X = C/(T − θ‎) where C is a constant for each material, T is the temperature in kelvins, and θ‎ is the Curie temperature in kelvins. The law was formulated by the French physicists Pierre Curie (1859–1906) and Pierre-Ernest Weiss (1865–1940).