"Who formulated the ""Law"" that, in a paramagnetic material, the magnetization of the material is (approximately) directly proportional to an applied magnetic field, but if the material is heated, the magnetization is (approximately) inversely proportional to temperature?"
Curie's law argument, and the opposite limit is likewise recovered. Curie's law In a paramagnetic material, the magnetization of the material is (approximately) directly proportional to an applied magnetic field. However, if the material is heated, this proportionality is reduced: for a fixed value of the field, the magnetization is (approximately) inversely proportional to temperature. This fact is encapsulated by Curie's law, after Pierre Curie: where This relation was discovered experimentally (by fitting the results to a correctly guessed model) by Pierre Curie. It only holds for high temperatures, or weak magnetic fields. As the derivations below show, the magnetization saturates in
Spontaneous magnetization the two regimes is given by it is easy to check two limits of this interpolation that follow laws similar to the Bloch law, for formula_5, and the critical behavior, for formula_6, respectively. Spontaneous magnetization Spontaneous magnetization is the appearance of an ordered spin state (magnetization) at zero applied magnetic field in a ferromagnetic or ferrimagnetic material below a critical point called the Curie temperature or . Heated to temperatures above , ferromagnetic materials become paramagnetic and their magnetic behavior is dominated by spin waves or magnons, which are boson collective excitations with energies in the meV range. The magnetization