Modeling oxygen isotope shifts and line-broadening effects of the 502-cm sup minus 1 Raman mode of YBa sub 2 Cu sub 3 O sub 7 minus x

Journal Article · Fri Feb 01 04:00:00 EST 1991 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.43.2771· OSTI ID:5885839

Altendorf, E; Chrzanowski, J; Irwin, J C ^[1]; Franck, J P ^[2]

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1. Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada V5A1S6 (CA)
2. Department of Physics, University of Alberta, Edmonton, Alberta (Canada)

Raman scattering experiments have been carried out on sintered pellets of YBa{sub 2}Cu{sub 3}{sup 18}O{sub 7{minus}{ital x}} and YBa{sub 2}Cu{sub 3}{sup 16}O{sub 7{minus}{ital x}}, obtained both by gas exchange and by growth with substituted oxides. The frequencies of the modes at 340, 435, and 500 cm{sup {minus}1}, which involve motion of the oxygen atoms and which shift significantly upon oxygen-isotope substitution, have been measured for several sets of samples. The 500-cm{sup {minus}1} line of the {sup 18}O samples is observed to be isotope shifted to a lesser degree than the 340- and 435-cm{sup {minus}1} phonons, and is significantly broadened. To model the observed behavior of the 500-cm{sup {minus}1} mode, a linear chain of O and Cu atoms is used to compute first-order {ital k}{congruent}0 Raman cross sections from 400 to 600 cm{sup {minus}1}. Disorder is introduced by randomly substituting {sup 18}O atoms for {sup 16}O atoms at positions in the chain corresponding to O(4) in the YBa{sub 2}Cu{sub 3}O{sub 7} lattice. Comparison of computed and experimental spectra suggest that the maximum linewidth in the 500-cm{sup {minus}1} peak occurs for a relative {sup 18}O concentration ({sup 18}O(4))/({sup 16}O(4)) between 24% and 36%. In addition, the 502-cm{sup {minus}1} peak position is found to depend nonlinearly on the relative {sup 18}O concentration. The implications of these results are discussed in terms of the currently accepted models for oxygen-isotope exchange in YBa{sub 2}Cu{sub 3}O{sub 7}

• OSTI ID: 5885839
• Journal Information: Physical Review, B: Condensed Matter; (USA), Journal Name: Physical Review, B: Condensed Matter; (USA) Vol. 43:4; ISSN PRBMD; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
HIGH-TC SUPERCONDUCTORS
ISOTOPES
LATTICE VIBRATIONS
OXIDES
OXYGEN COMPOUNDS
RAMAN SPECTRA
SPECTRA
SPECTRAL SHIFT
STRUCTURAL MODELS
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
YTTRIUM OXIDES