LAUSR

Abstract The effect of Cu doping on structural, magnetic and magnetocaloric properties in La 0.7 Sr 0.25 Na 0.05 Mn 1−x Cu x O 3 (x = 0, 0.05, 0.10, 0.15, 0.20) has been investigated. The samples were prepared by conventional solid-state reaction. Analysis of XRD patterns indicates that the samples are crystallized in a rhombohedral perovskite structure with R 3 c space group. Rietveld refinements reveal that the lattice parameter a and unit cell volume gradually increase up to x = 0.10 then decrease, while parameter c decreases with increasing Cu content. XPS spectra exhibit the coexistence of the Cu 2+ and Cu 3+ ions in the samples with x=0.15 and 0.20. Magnetization measurements show the Curie temperature Tc and the maximum magnetic entropy change ΔS M decrease with the increase in the Cu content, whereas the relative cooling power (RCP) is basically unaffected. The La 0.7 Sr 0.25 Na 0.05 Mn 0.9 Cu 0.1 O 3 sample shows a maximum ΔS M of 1.75 J kg −1  K −1 and a RCP of 87 J kg −1 at 320 K under a magnetic field change of 20 kOe, and can be one of the potential magnetic refrigerant materials for near room temperature application.