Weakly first-order or nearly second-order phase transitions

Abstract

Abstract In this study we have developed a model which is mainly for a spin system (Ising model) superimposed on a system of lattice vibrations (Einstein and/or Debye model). Under this model we have derived the thermodynamic functions and predicted their critical behaviour near Tc. Our predictions are that C v and β −1 have a temperature dependence described by a power law formula with critical exponent a, whereas C p and α remain constant but show anomalous behaviour near Tc. This then implies that the γ Gruneisen parameter remains constant throughout the phase transitions. Regarding some previous model studies, our predictions seem to indicate that the model under consideration exhibits a phase transition of weakly first-order or nearly second-order.