Electronic and local structural properties of the Bi{sub 2}Sr{sub 2}(Ca{sub 1{minus}x}Y{sub x})Cu{sub 2}O{sub 8+{delta}} family of materials, studied by X-ray absorption spectroscopy
The hole distribution of overdoped, optimum-doped and underdoped states in the series Bi{sub 2}Sr{sub 2}(Ca{sub 1{minus}x}Y{sub x})Cu{sub 2}O{sub 8+{delta}} compounds has been investigated by high-resolution O K-edge and Cu L-edge X-ray absorption near-edge-structure (XANES) spectra. Near the O 1s edge, a well-pronounced pre-edge peak with maximum at {approximately}528.3 eV is found and is ascribed to the excitations of O 1s electron to O 2p hole states located in the CuO{sub 2} planes. The intensity of this pre-edge peak decreases as the Y doping increases, demonstrating that the chemical substitution of Y{sup 3+} for Ca{sup 2+} in Bi{sub 2}Sr{sub 2}(Ca{sub 1{minus}x}Y{sub x})Cu{sub 2}O{sub 8+{delta}} gives rise to a decrease in hole concentrations within the CuO{sub 2} planes. The results from the Cu L-edge X-ray absorption spectra are consistent with those from O 1s X-ray absorption spectra. The local structure of the pyramidal CuO{sub 5} in Bi{sub 2}Sr{sub 2}(Ca{sub 1{minus}x}Y{sub x})Cu{sub 2}O{sub 8+{delta}} has been determined from extended X-ray absorption fine-structure (EXAFS) spectra. It was found that the axial Cu-O bond distances contract and the equatorial Cu-O bond distances expand as the Y content increases. Such results are strongly correlated to a decrease in the hole concentration within the CuO{sub 2} plane, which controls the superconductivity.
- Research Organization:
- National Taiwan Univ., Taipei (TW)
- OSTI ID:
- 20075560
- Journal Information:
- Chemistry of Materials, Vol. 12, Issue 4; Other Information: PBD: Apr 2000; ISSN 0897-4756
- Country of Publication:
- United States
- Language:
- English
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