IR-active optical phonons in Pnma-1, Pnma-2 and R3c phases of LaMnO_{3+δ}
Infrared-active phonons in LaMnO_{3+δ} were studied by means of the reflection and transmission spectroscopy from 50 to 800 cm^{-1} at room temperature. Powder and ceramic samples of the phases of Pnma-2 (δ=0.02), Pnma-1 (δ=0.08), and R3c (δ=0.15) were investigated. Besides, energies of the dipole-active phonons in Pnma-2, Pnma-1 phases were obtained by lattice-dynamics calculations. The transformations of IR-active phonons with the increase of δin the sequence of Pnma-2, Pnma-1, R3c are discussed.
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