Magnetocaloric Effect Simulation in La0.8Na0.2MnO3-Δ Nanopowders

The critical behavior of La0.8Na0.2MnO3-Δ nanopowders at the paramagnetic to ferromagnetic phase
transition is studied. The optimized critical exponents, through an iterative program based on Kouvel
Fisher method, were found to be as: 𝜸 = 𝟏.𝟎𝟓; 𝜷 = 𝟎.𝟒𝟓. These obtained critical exponents does not match
with the conventional universality classes. In addition, these 𝜸 and 𝜷 values are close the ones predicted by
the mean-filed theory (𝜸 = 𝟏 and 𝜷 = 𝟎.𝟓). It has been approved that the estimated critical temperature and
the critical exponents are unambiguous and intrinsic to the La0.8Na0.2MnO3-Δ nanopowders. Based on the
combination of the Landau model and the Arrott–Noakes equation, the isothermal magnetization curves and
the magnetocaloric effect have been successfully simulated.