文摘
Structural, magnetic and magnetocaloric properties of manganites series with the La0.5Ca0.5?xAgxMnO3 (0.0 ? x ? 0.4) compounds were investigated. Samples were synthesized using the solid state reaction at high temperature and analyzed by XRD data based on the Rietveld refinement technique. Samples with x = 0.0, 0.1, 0.2, 0.3 and 0.4 crystallized in orthorhombic symmetry with Pnma space group. Also, Magnetizations measurements were performed to investigate magnetic properties. Transition from ferromagnetic (FM) to charge ordered antiferromagnetic (CO-AFM) phases at low temperature is observed for Ag-free La0.5Ca0.5MnO3. Compounds with x = 0.2, 0.3 and 0.4, do not exhibit this transition, and only FM metallic phases are observed. The Curie temperature TC increases with increasing Ag amount from 222 K (for x = 0.0) to 264 K (for x = 0.2).While x > 0.2, TC remains substantially constant. Magnetic entropy change (¦¤SM) was estimated from isothermal magnetization data. Parent compound (x = 0.0) exhibits both normal (negative ¦¤SM) and inverse (positive ¦¤SM) magnetocaloric effects at TC and TCO, respectively. However, all the Ag doped samples show only normal magnetocaloric effect at TC. The Largest MCE occurs for sample with x = 0.4 (¦¤SM = 3.27 J kg?1 K?1, ¦¤H = 5 T) for which largest relative cooling power (RCP = 229.27 J kg?1, ¦¤H = 5 T) is reached as well.
