Raman Scattering Spectra of (Sm_2⁄3Ce_1⁄3)₂(Ba_2⁄3Sm_1⁄3)₂Cu₃O₉

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Polarized Raman spectra of (Sm_2⁄3Ce_1⁄3)₂(Ba_2⁄3Sm_1⁄3)₂Cu₃O₉ with the Cu–O₅ pyramid structure have been measured at room temperature using single crystals. Peaks have been observed at 450 and 525 cm⁻¹ in the A_1g symmetry configuration and at 200 cm⁻¹ in the B_1g configuration. A peak due to a Raman-forbidden mode has been observed at 560 cm⁻¹. The B_1g symmetry peak is assigned to the out-of-phase bending of oxygen in the Cu–O₂ plane. The energy of this mode is much lower than that of YBa₂Cu₃O₇ (330 cm⁻¹). On the other hand, the energies of the A_1g-symmetry peaks are nearly the same as those in YBa₂Cu₃O₇ (440 and 500 cm⁻¹), suggesting that these two peaks are associated with the vibrations of apical oxygen.