Structural, magnetic and magnetocaloric investigation of La_0.67Ba_0.33Mn_1−xNi_xO₃ (x = 0, 0.025 and 0.075) manganite

In this paper, we report the structural, magnetic and magnetocaloric properties of Ni-doped La_0.67Ba_0.33Mn_1−xNi_xO₃ (x = 0, 0.025 and 0.075) manganites. Our compounds were synthesized using the sol–gel method. The structural analysis using Rietveld refinement shows that Ni-doped LaBaMnO₃ system crystallizes in the rhombohedral symmetry with \({\text{R}}\bar {3}{\text{c}}\) space group. Magnetization measurements versus temperature in a magnetic applied field of 0.05 T reveal that all the compositions exhibit a transition from a ferromagnetic to paramagnetic phase with increasing temperature. A systematic decrease in the transition temperature is clearly observed upon Ni doping and a near room temperature T_C (302 K) is achieved with x = 0.075 composition. The maximum magnetic entropy change \(\left( { - ~\Delta {\text{S}}_{{\text{M}}}^{{\hbox{max} }}} \right)\) in a magnetic field change of 5 T is found to be 2.12, 2.78 and 1.78 J/kg K for x = 0, 0.025 and 0.075, respectively. At this value of magnetic field, large relative cooling power values are obtained in our samples, especially for x = 0.075 (271 J/kg) making it a promising candidate for magnetic refrigeration near room temperature.