Infrared absorption spectra of manganese oxides La1−x−yRyCaxMnO3−δ

Infrared transmission spectra were measured systematically in polycrystalline La1−xCaxMnO3−δ and several systems substituted by other rare earth (RE) ions such as Sm3+, Gd3+, Dy3+, etc., at La3+ sites or Fe ions at Mn sites but keeping the nominal Mn4+/Mn3+≈3/7. Two strong absorption peaks located around 600 and 350 cm−1, which are associated with internal phonon modes, i.e., stretching and bending modes of MnO6 octahedra, have been observed. Both of them are influenced by the concentrations of Ca and other RE ions substituting at the La and Mn sites. The details of the absorption peaks will be discussed on the basis of changes of the bond length of Mn-O and bond angle of Mn-O-Mn in MnO6 octahedra.