Large magnetocaloric effect in manganese perovskite La_0.67- Bi Ba_0.33MnO₃ near room temperature

La_0.67- Bi Ba_0.33MnO₃ (x = 0 and 0.05) ceramics were prepared via the sol-gel method. Structural, magnetic and magnetocaloric effects have been systematically studied. X-ray diffraction shows that all the compounds crystallize in the rhombohedral structure with the R3̄c space group. By analyzing the field and temperature dependence of magnetization, it is observed that both samples undergo a second order magnetic phase transition near T _C. The value of T _C decreases from 340 K to 306 K when increasing x from 0.00 to 0.05, respectively. The reported magnetic entropy change for both samples was considerably remarkable and equal to 5.8 J kg^-1 K^-1 for x = 0.00 and 7.3 J kg^-1 K^-1 for x = 0.05, respectively, for μ ₀ H = 5 T, confirming that these materials are promising candidates for magnetic refrigeration applications. The mean-field theory was used to study the magnetocaloric effect within the thermodynamics of the model. Satisfactory agreement between experimental data and the mean-field theory has been found.