IR-active optical phonons in Pnma-1, Pnma-2 and R3¯c phases of LaMnO3+δLaMnO3+δ

Infrared-active phonons in LaMnO3+δLaMnO3+δ were studied by means of the reflection and transmission spectroscopy from 50 to 800cm-1 at room temperature. Powder and ceramic samples of the phases of Pnma-2(δ=0.02),Pnma-1(δ=0.08) and R3¯c(δ=0.15) were investigated. In addition, 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 in δδ in the sequence of Pnma-2, Pnma-1, R3¯c are discussed.