Effect of A-site-substitution on structural, magnetic and magnetocaloric properties in La0.7Sr0.3 Mn0.9Cu0.1O3 manganite

The effect of bismuth and calcium substitution on the structure, magnetic and magnetocaloric properties in La_0.7Sr_0.3Mn_0.9Cu_0.1O₃ manganite compounds were investigated. All the samples were synthesized using the conventional sol-gel route. The structural analysis revealed that our compounds crystalize in the rhombohedral structure ($R\stackrel{-}{3}$c space group), at room temperature. The magnetic measurements showed that all the studied compounds exhibited a second order paramagnetic (PM)-ferromagnetic (FM) transition at Curie temperature T_C ranging between 290 and 320 K. The magnetic entropy change $(-\Delta S_M)$ values estimated by the Landau theory are very close to those obtained using the classical Maxwell relation. Under an applied field μ₀H = 5 T, the maximum of the magnetic entropy change $(-\Delta S_M^{\max })$ and the relative cooling power (RCP) are found to be 3.06 J/kg.K and 198 J/kg for La_0.7Sr_0.3Mn_0.9Cu_0.1O₃, 3.39 J/kg.K and 161 J/kg for La_0.6Bi_0.1Sr_0.3Mn_0.9Cu_0.1O₃, and 3.65 J/kg.K and 184 J/kg for La_0.6Bi_0.1Sr_0.25Ca_0.05Mn_0.9Cu_0.1O₃. These obtained values were compared with those of some other reported manganite and showed that our compounds could be as promising candidates for magnetic refrigeration.