First-order magnetic phase transitions

Abstract

After the general properties of the first-order magnetic phase transitions between ordered structures were investigated, the number of possible models has been limited by supposing the sensitivity of the exchange energy to the interatomic distance to be responsible for the phase transition. It has shown that the magnetic phase transition occurs as a result of a sign-change in the proper combination of the exchange parameters. The transition may be influenced by the variation of the pressure and the magnetic field. The actual phase transition is, however, hindered in both directions by the elastic energy wall, separating the free energy minima of the different phases. The T – P phase diagram has been calculated and the conditions for the existence of a triple point in the T – P plane have been investigated in the case of antiferromagnetic ↔ ferromagnetic transitions. The temperature hysteresis, i.e. the difference between the upper (Tsup) and lower (Tinf) transition temperatures has been determined at different pressures and for both temperatures a linear dependence has been obtained. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34842