Local structure, magnetization and Griffiths phase of self-doped La1−xMnO3+δ manganites

Self-doped La1−xMnO3+δ manganites (x = 0.0, 0.05, 0.1, and 0.15) have been studied by X-ray diffraction, X-ray absorption near K-edge spectroscopy and magnetization measurements. The x = 0.0 composition is the orthorhombic Pnma   phase with a small amount of the rhombohedral R3¯c one, the compounds with x = 0.05, 0.1 and 0.15 exhibit the R3¯c space group. The Curie temperature, TC, increases with x increase substantially. The TC of the x = 0.1 and x = 0.15 samples are almost the same, but magnetization of the x = 0.15 composition is much higher than that of the x = 0.1 sample. The results for the x = 0.15 sample are in agreement with the suggestion that a part of manganese ions, being in a trivalent state, occupies a vacant A-site of the perovskite ABO3 cell. Magnetic behavior of the samples above TC exhibits Griffiths-like features. The observed Griffiths singularity is suggested to be due to strain accommodation caused by the vacancies in the A- and B-positions of the ABO3 perovskite cell.

► Mn3+ ions form the anti-site defects in A-site of ABO3 perovskite cell for x > 0.1 sample.
► Griffiths-like singularity is originated by strain accommodation field.
► Strain accommodation is caused by the vacancies in A- and B-sites of the perovskite cell.