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1 November 1990 Systematic Raman study on Tl-based superconductors with Tc variation due to oxygen deficiency
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Using a Raman microprobe technique, we have measured the Raman spectra of singile crystaillites of Ti2Ba2Ca-lCu02fl+4-d (n1,2 and 3) with Tc varied by oxygen removal or addition. It is found in Ti2Ba2CuO6-d that the phonon modes associated with the vibrations of bridging 02 in Ba-0 planes (-"485 cnr') and 03 in 11-0 pianes (--600 cm ' ) increase i n frequency and become broader as the Ic increases from 0 to 70 K with oxygen removai, whiie the Ba and TIE vibration modes do not change appreciabily. The observations are attributed to the vallence change of TI., resuilting from a change in the charge transfer between H and (Cu-Ol), and to the distortion and/or disorder in 11-0 planes due to the oxygen removal.. In TI2Ba2CaCu2O8d and TlI2Ba2Ca2Cu3OlOd, the frequencies of 02 and 03 vibration modes increase with Tc raised by oxygen addition, while the Iow-frequency modes do not change. There is a ciear correlEation between Tc and phonon frequencies in fl-based superconductors. We suggest that a change in charge distribution in (Cu-01)-02-(fl-03) complexes is responsibEe for the phonon frequency shifts observed in 02 and 03 vibration modes.
© (1990) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Kiyoto Matsuishi, Y. Q. Wang, Y. Y. Sun, J. G. Lin, Peiherng Hor, Michael A. Gorman, and C. W. Chu "Systematic Raman study on Tl-based superconductors with Tc variation due to oxygen deficiency", Proc. SPIE 1336, Raman and Luminescence Spectroscopies in Technology II, (1 November 1990);

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