In magnetism, the Curie constant is a material-dependent property that relates a material's magnetic susceptibility to its temperature through Curie's law.
The Curie constant when expressed in SI units, is given in kelvins (K), by
where is the number of magnetic atoms (or molecules) per unit volume, is the Landé g-factor, is the Bohr magneton, is the angular momentum quantum number and is Boltzmann's constant. For a two-level system with magnetic moment , the formula reduces to
while the corresponding expressions in Gaussian units are
The constant is used in Curie's law, which states that for a fixed value of an applied magnetic field , the magnetization of a material is (approximately) inversely proportional to temperature.
This equation was first derived by Pierre Curie.
Because of the relationship between magnetic susceptibility , magnetization and applied magnetic field is almost linear at low fields, then
this shows that for a paramagnetic system of non-interacting magnetic moments, magnetization is inversely related to temperature .