Electron structure, Raman “vacancy” modes and Griffiths-like phase of self-doped Pr1-xMnO3+δ manganites

A complex analysis of the vacancy-doped Pr1-xMnO3+δ (x = 0.0, 0.2) manganites is performed by x-ray diffraction, Raman and x-ray photoelectron spectroscopy, and magnetic measurements to study the features of electron, phonon and magnetic structure of the compounds. The x = 0.0 oxide belongs to orthorhombic Pnma structure, while the x = 0.2 exhibits pseudo cubic symmetry. Average valence of manganese for both samples is found to be ≈ 3.2 due to doping holes localized in the O 2p states and the hybridization of Mn 3d and O 2p states. Observed unusually large intensity of the Raman mode at 650 cm−1 is assumed to be related to a high level of vacancies, while the vacancies suppress both the Jahn-Teller (485 cm−1) and charge-transfer d-d (610 cm−1) Raman modes. Griffiths-like singularity are firstly observed for the Pr1-xMnO3+δ manganites. The singularity is supposed to be originated from the vacancies and strain accommodation.