Oxygen Deficiency Effects upon Structural, Magnetic and Electrical Properties of Doped Manganite Oxides

The effects of the oxygen deficiency on structural, magnetic and electrical properties of La 0.7 Sr 0.3 MnO 3-δ □ δ manganites, where □ is a vacancy (0 ≤ δ < 0.15), have been investigated. The vacancy powder samples were synthesized using a new technique. A structural phase transition separating a rhombohedral phase and an orthorhombic phase was observed at a concentration of Mn 3+ around 85% to 90% per Mn atom in the unit formula. These compounds exhibit ferromagnetic metallic behavior for δ < 0.1 and antiferromagnetic insulator behavior for 0.125 < δ < 0.15. A charge ordering seems to appear below T = 115 K in the La 0.7 Sr 0.3 MnO 2.9 (δ = 0.1) specimen. The structural and magnetic transitions are very sensitive to the vacancy rate.