Structural and magnetic properties in the self-doped perovskite manganites with nominal composition La0.7Sr0.3−xMnO3−δ

Abstract Perovskite manganites with nominal composition La 0.7 Sr 0.3− x MnO 3− δ (0.00≤ x ≤0.20) have been prepared by the sol–gel method with the highest heat treatment temperature being 1073 K. The XRD patterns indicate that when the doping level is x≤ 0.10 the samples have only a single phase, with the R3c perovskite structure, while for x> 0.10, the samples have two phases with the R3c perovskite being the dominant phase and Mn 3 O 4 being the second phase. A quantitative analysis and Rietveld fitting of the X-ray powder diffraction data indicate that on the basis of the thermal equilibrium theory of crystal defects there are Mn 2+ ions at the A sites and Mn 3+ plus Mn 4+ ions at the B sites in the ABO 3 perovskite phase. The curves of magnetization versus applied magnetic field at 10 K showed that the magnetic moments of the Mn 2+ ions at the A sites are antiparallel to those of the Mn 3+ and Mn 4+ ions at the B sites.