Raman study of phonons in Sr3Mn2O6.54 and Sr3Mn2O7 layered manganites

Abstract Polycrystalline Sr 3 Mn 2 O 6.54 and Sr 3 Mn 2 O 7 layered manganites were studied at room temperature using Raman spectroscopy. While the phonon spectrum of the stoichiometric Sr 3 Mn 2 O 7 sample is consistent with the group theoretical analysis for the I 4/mm structure, three additional modes are observed in the phonon spectrum of the oxygen-deficient Sr 3 Mn 2 O 6.54 sample. Based on an analysis of the temperature dependence of the Raman spectrum of Sr 3 Mn 2 O 6.54 and a comparison with the Raman spectrum of LaSr 2 Mn 2 O 7 , we conclude that the ‘extra’ modes should be viewed as disorder-induced Raman scattering.