Comment on ``Raman spectroscopy study of NaxCoO2 and superconducting NaxCoO2•yH2O ''
Abstract
The effect of surface degradation of the thermolectric cobaltite on Raman spectra is discussed and compared to experimental results from Co3O4 single crystals. We conclude that on NaCl-flux grown NaxCoO2 crystals a surface layer of Co3O4 easily forms that leads to the observation of an intense phonon around 700cm-1 [Y. G. Shi , Phys. Rev. B 70, 052502 (2004)]. The Raman spectra on freshly cleaved crystals from optical floating zone ovens do not show such effects and have a high-frequency phonon cutoff at approximately 600cm-1 [P. Lemmens , Phys. Rev. Lett. 96, 167204 (2006)]. We discuss the relation of structural dimensionality, electronic correlations, and the high-frequency phonon cutoff of the thermolectric cobaltite.
- Publication:
-
Physical Review B
- Pub Date:
- March 2007
- DOI:
- 10.1103/PhysRevB.75.106501
- arXiv:
- arXiv:cond-mat/0701583
- Bibcode:
- 2007PhRvB..75j6501L
- Keywords:
-
- 75.30.Kz;
- 64.70.Rh;
- 71.38.-k;
- 75.50.Cc;
- Magnetic phase boundaries;
- Commensurate-incommensurate transitions;
- Polarons and electron-phonon interactions;
- Other ferromagnetic metals and alloys;
- Condensed Matter - Strongly Correlated Electrons;
- Condensed Matter - Materials Science
- E-Print:
- 2 pages, 1 figure, to be published in Phys. Rev. B (2007)