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Hole State Density of La1-xSrxCoO^d3-Δ} (0less then or equal to}xless then or equal to}0.5) Across the Insulator/Metal Phase Boundary



A R. Moodenbaugh, B Nielson, S Sambasivan, Daniel A. Fischer, T Friessnegg, S Aggarwal, R Ramesh, B Pfeffer


The oxygen K near edge x-ray absorption fine structure (NEXAFS) of polycrystalline and film La1-xSrxCoO3-d at room temperature was studied using fluorescence yield techniques. The bulk sensitive nature of fluorescence yield (relative to electron yield), combined with the 0.2 eV incident photon resolution, allow us to accurately determine the evolution with x and d of the oxygen K NEXAFS. For LaCoO3, a complex pre-peak is centered near an energy E=530.5 eV. This peak, which has a full width at half maximum of about 3.0 eV, has been identified with oxygen bonding to Co 3d electrons. With Sr substitution we observe a distinct oxygen hole peak with intensity proportional to x, centered near E=528.8 eV, with full width at half maximum of 1.2 eV. In oxygen-reduced samples the hole peak tends to decrease in intensity as oxygen is removed. Comparisons are made with theoretical work and with earlier oxygen K near-edge studies on similar materials, most of which utilized electron yield. The behavior of the pre-peak features with Sr (hole) doping parallels that observed in the oxide superconductors. Rutherford Backscattering results and oxygen K NEXAFS of La0.5Sr0.5CoO3-d thin films of are compared with each other and with bulk results to estimate relative oxygen contents of the films.
Physical Review B (Condensed Matter and Materials Physics)
No. 8


ceramics, electronic transitions, metal-insulator transitions, NEXAFS, refractories, x-ray absorption spectroscopy


Moodenbaugh, A. , Nielson, B. , Sambasivan, S. , Fischer, D. , Friessnegg, T. , Aggarwal, S. , Ramesh, R. and Pfeffer, B. (2000), Hole State Density of La<sub>1-x</sub>Sr<sub>x</sub>CoO^d3-{&#916;} (0{less then or equal to}x{less then or equal to}0.5) Across the Insulator/Metal Phase Boundary, Physical Review B (Condensed Matter and Materials Physics) (Accessed April 17, 2024)
Created January 31, 2000, Updated October 12, 2021