The temperature at which a material loses its ability to retain magnetism, that is, where it changes from ferromagnetic to paramagnetic behavior. Below this temperature, atoms interact so that their magnetic moments couple and behave collectively. At the Curie temperature the atom’s thermal energy equals the coupling energy, and above this temperature the atomic magnetic moments are not coupled and the substance behaves paramagnetically. The Curie temperature of most rocks is approximately 550°C which is usually reached at depths of 30–40 km. The analogous point with antiferromagnetic materials is the Neel point.