Raman study of HgBa2Can−1CunO2n+2+δ (n=1,2,3,4 and 5) superconductors |
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Authors: | Xingjiang Zhou M Cardona C W Chu Q M Lin S M Loureiro and M Marezio |
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Institution: | a Max-Planck-Institut für Festkörperfforschung, Heisenbergstrasse 1, D-70569, Stuttgart, Germany b Department of Physics and the Texas Center for Suuperconductivity at the niversity of Houston, Houston, Texas 77204-5932, USA c Laboratoire de Cristallographie, CNRS-UJF, BP 166, 38042, Grenoble Cedex 09, France |
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Abstract: | Polarized micro-Raman scattering measurements have been performed on the five members of the HgBa2Can−1CunO2n+2+δ (n=1,2,3,4 and 5) high-Tc superconductor family using different laser frequencies. Local laser annealing measurements were carried out to investigate the variation of the Raman spectra with the excess oxygen content, δ. A systematic evolution of the spectra, which display mainly peaks near 590, 570, 540 and 470 cm−1, with increasing number of CuO2 layers has been observed; its origin has been shown to lie in the variation of the interstitial oxygen content. In addition to confirming that the 590 cm−1 mode represents vibration of apical oxygens in the absence of neighboring excess oxygen, the 570 cm−1 mode, which may be composed of some finer structures, has been assigned to the vibration of the apical oxygen modified by the presence of the neighboring excess oxygens. The 540 and 470 cm−1 modes may represent the direct vibration of excess oxygens. The implication of possible different distribution sites of excess oxygens is discussed. All other observed lower-frequency modes are also assigned. |
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