Influence of magnesium doping the structural and magnetocaloric properties of manganites oxide prepared by sol–gel method

We have investigated the effect of Mg doping on structural, magnetic and magnetocaloric properties of a novel series of LaSrBaMnMgO (0 ≤ x ≤ 0.2) perovskites elaborated by a sol–gel method. These oxides were characterized by neutron powder diffraction (NPD) at room temperature and magnetization measurements versus temperature and various applied magnetic fields. Rietveld refinements from NPD data indicate an orthorhombic structure (Pnma) for all the compounds (x = 0 to x = 0.2); in all the samples with x > 0, Mg is distributed at random in the Mn positions of the perovskite. Magnetization measurements show a ferromagnetic behavior for x = 0 and x = 0.1 samples, whereas the compound x = 0.2 introduces a magnetic glass state (cluster or spin glass). The magnetic entropy change (|Δ S|) and the relative cooling power are, respectively, 2.46, 1.85 and 0.83 J kg K and 169, 101 and 116 J kg at a field change of 5 T, for all compounds x = 0, 0.1 and 0.2. These results are compared with those of some other reported manganites, helping to understand the magnetic arrangement required for magnetic refrigeration.