Phonons in (Sm,Ce)₂(Ba,Sm)₂Cu₃O_x

Abstract

Polarized Raman spectra of (Sm,Ce)₂(Ba,Sm)₂Cu₃O_x which has Cu-O₅ pyramid structure as well as YBa₂Cu₃O₇ have been measured at room temperature using single crystals. Peaks have been observed at 442 and 537 cm⁻¹ in the A_lg symmetry configuration and at 200cm⁻¹ in the B_1g A peak due to a Raman-forbidden mode has been observed at 560cm⁻¹. The B_1g symmetry peak is assigned to the out-of-phase bending of oxygen in tee Cu-O₂ plane. The energy of this mode is much lower than that of YBa₂Cu₃O₇ (330cm⁻¹). On the other hand, energies of the A_g-symmetry peaks are nearly the same as those in YBa₂Cu₃O₇ (440 and 500cm⁻¹, respectively), suggesting that these two peaks are associated with the vibrations of apical oxygen.