Large magnetocaloric effect in manganese perovskite La0.67−xBixBa0.33MnO3 near room temperature

Abstract

La_0.67−xBi_xBa_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 Rc 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 μ₀H = 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.