Thus, below \(T_c\) the system is in the ferromagnetic phase, with one of two possible directions of the average spontaneous magnetization, so that the critical (Curie 39 ) temperature, given by Equat...Thus, below \(T_c\) the system is in the ferromagnetic phase, with one of two possible directions of the average spontaneous magnetization, so that the critical (Curie 39 ) temperature, given by Equation (\ref{72}), marks the transition between the paramagnetic and ferromagnetic phases. (Since the stable minimum value of the free energy \(F\) is a continuous function of temperature at \(T = T_c\), this phase transition is continuous.)
