Curie temperature Ferromagnetism

as temperature increases, thermal motion, or entropy, competes ferromagnetic tendency dipoles align. when temperature rises beyond point, called curie temperature, there second-order phase transition , system can no longer maintain spontaneous magnetization, ability magnetized or attracted magnet disappears, although still responds paramagnetically external field. below temperature, there spontaneous symmetry breaking , magnetic moments become aligned neighbors. curie temperature critical point, magnetic susceptibility theoretically infinite and, although there no net magnetization, domain-like spin correlations fluctuate @ length scales.

the study of ferromagnetic phase transitions, via simplified ising spin model, had important impact on development of statistical physics. there, first shown mean field theory approaches failed predict correct behavior @ critical point (which found fall under universality class includes many other systems, such liquid-gas transitions), , had replaced renormalization group theory.