Scaling analysis of PM–FM phase transition in Nd0.5Sr0.25Ca0.25MnO3 based on magnetic entropy change

Abstract

The dependence of magnetization M on temperature T and the applied magnetic field H were measured for the half-doping manganite Nd0.5Sr0.25Ca0.25MnO3. The M(T) curve exhibits that a paramagnetic (PM)–ferromagnetic (FM) phase transition occurs around 174 K. The PM–FM phase transition is considered to be a second-order phase transition due to the absence of hysteresis on its heating and cooling M(T) curves. Moreover, the second-order phase transition can be testified with the positive slope in Arrott plots. However, the scaling analysis of magnetic entropy change exhibits that ΔSM(T) curves do not collapse into a single universal curve, indicating that the observed PM–FM phase transition is not an authentic second-order phase transition. Due to the appearance of short-range FM coupling in PM region, the PM–FM phase transition at 225 K > T > 188 K is a first-order phase transition. The second-order phase transition only occurs at T < 188 K. When the magnetic field is increased above 1.5 T, the first-order phase transition can be converted into the second-order phase transition. The results shows that the magnetic entropy change scaling is an effective method to determine the nature of the PM–FM phase transition.