Magnetocaloric effect study by means of theoretical models and spontaneous magnetization determination in Ni0.4Mg0.3Cu0.3Fe2O4 ferrite

The magnetocaloric effect (MCE) of Ni0.4Mg0.3Cu0.3Fe2O4 ferrite was analyzed by different theoretical methods such as mean-field, Bean-Rodbell and Landau theories. Results confirm the second order type of the ferromagnetic (FM)-paramagnetic (PM) magnetic phase transition for the sample. The values of magnetic entropy change (-Delta S-M) estimated from each theory agree well with those experimentally determined using Maxwell relations. The spontaneous magnetization values (M-spont(T)) determined from both (-Delta S-M versus M-2) and (H/M versus M-2) data are very close, confirming the validity of the magnetic entropy change to estimate M-spont (T) values. The critical exponents (beta, gamma and delta) obtained for Ni0.4Mg0.3Cu0.3Fe2O4 sample at its Curie temperatures (T-C) are close to those predicted in mean-field model.