Abstract

We present normal mode assignments for the Raman spectra of 1–2–3-type materials on the basis of polarized Raman studies of single crystals of Ba₂YCu₃O₇, Ba₂YCu₃O₆, Sr₂YCu_2.4Al_0.6O₇, and Ba_2−xLa_1+xCu₃O_7+δ. In Ba₂YCu₃O₇ we observe five intrinsic modes at 500 [O(1) axial stretch], 435 [in-phase O(2), O(3) bend], 335 [out-of-phase O(2), O(3) bend], 140 [Cu(2) axial stretch mode], and 118 cm⁻¹ (Ba axial mode). Defect-induced modes are found at 600 and 220 cm⁻¹. A mode at 640 cm⁻¹, which is seen only in ceramics, is shown to be due to a BaCuO₂ impurity phase. Furthermore, we discuss the Raman spectra of Bi₂Sr₂Ca_n−1Cu_nO_4+2n and the high-frequency (ω > 1000 cm⁻¹) scattering in Ba₂YCu₃O₆ and Ba₂YCu₃O₇.

© 1989 Optical Society of America

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