Study of the Magnetocaloric Effect by Means of Theoretical Models in La_0.6Ca_0.2Na_0.2MnO₃ Manganite Compound

In this work, an overview of the Weiss molecular mean-field theory, the Bean–Rodbell model and the Landau theory is presented, providing the theoretical background for simulating the magnetocaloric properties for La_0.6Ca_0.2Na_0.2MnO₃ manganite. Results showed that sample exhibits second-order ferromagnetic (FM)–paramagnetic (PM) magnetic phase transition and relatively higher values of magnetic entropy change (−∆S_M). In application point of view, this material can be used in magnetic refrigeration technology. The theoretical values of −∆S_M determined using each theory agree well with the experimental ones estimated from Maxwell relations. In other part, a good agreement in the spontaneous magnetization values, M_spont(T), estimated from (−∆S_M vs. M²) and (H/M vs. M²) data was found. Also, the values of the critical exponent (β) found from both methods are close and check that the mean-field model is adequate to study the MCE in La_0.6Ca_0.2Na_0.2MnO₃ sample.