Effect of partial substitution of Mn by Fe on the structure, magnetic phase transition and magnetocaloric response in La_0.67Pb_0.33Mn_1−xFe_xO₃ compounds

The compounds La_0.67Pb_0.33Mn_1−xFe_xO₃ (0 ≤ x ≤ 0.10) have been fabricated by ceramic procedures mainly to investigate their structure, magnetic phase transition and magnetocaloric effect. All samples have a rhombohedral structure belonging to $R\overline{3}C$ space group by structural analysis. As the Fe concentration x increases up to 0.10, Curie temperature value significantly decreases from 360 to 210 K. The maximum values of MEC (magnetic entropy change) are found to be 4.17, 2.99, 2.58 J kg⁻¹ K⁻¹ under 5 T field change for x = 0, 0.05, 0.10, respectively. The corresponding values of RCP (relative cooling power) are 229.8, 235.4, 216.5 J kg⁻¹. The relatively large MEC, high RCP values and the convenient adjustment of the T_C suggest that the prepared La_0.67Pb_0.33Mn_1−xFe_xO₃ compounds could be appropriate materials for magnetic cooling in a wide working temperature range. The analysis of isothermal magnetization using the Arrott curves and Franco's universal method reveals that the La_0.67Pb_0.33Mn_1−xFe_xO₃ manganites show a second-order ferromagnetic–paramagnetic transition.