Large magnetocaloric effect in manganese perovskite La_0.67−xBi_xBa_0.33MnO₃ near room temperature

Abstract

La_{0.67-<i>x</i>} Bi _<i>x</i> Ba_0.33MnO₃ (<i>x</i> = 0 and 0.05) ceramics were prepared <i>via</i> 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 <i>R</i>3̄<i>c</i> 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 <i>T</i> _C. The value of <i>T</i> _C decreases from 340 K to 306 K when increasing <i>x</i> 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 <i>x</i> = 0.00 and 7.3 J kg^-1 K^-1 for <i>x</i> = 0.05, respectively, for <i>μ</i> ₀ <i>H</i> = 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.