Analysis of infrared reflection spectra of oxides of the La2CuO4 high-Tc superconductor family in polarized light
F. Gervais, P. Echegut, J. M. Bassat, P. Odier
DOI 10.1103/PhysRevB.37.9364 · Physical Review B
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Abstract
The temperature dependence of infrared reflection spectra of La2NiO4 single crystal in polarized light between 10 and 750 K is analyzed and compared to the results for an oriented sample of La2CuO4. In both compounds, the spectra are found to reflect the bidimensional character of this family of compounds with a plasmon restricted to the basal a−b plane. In the nickel compound, the plasma frequency increases with temperature according to a simple scheme of semiconducting behavior with thermal filling of an empty conduction band, consistent with the d8 character of Ni. Conversely, in "metallic" La2CuO4 (d9 character) the plasmon is found to shift little with temperature. The analysis of a number of results obtained with ceramics samples in superconducting and normal phases are reexamined under the light of these new data. The effective charges carried by the oxygen ions are also deduced from the splittings of polar modes into transverse and longitudinal components. Results confirm the strong anisotropy of the transition-metal-oxygen bonds with strong overlap in the basal plane related to the short bond lengths and much more ionic character along the tetragonal c axis.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| La2CuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | — | Pressure not reported | unknown |
| La1.85Sr0.15CuO4-y Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | — | Pressure not reported | unknown |
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