Cu K -edge x-ray-absorption near-edge structure and electronic structure of Nd sub 2 minus x Ce sub x CuO sub 4 minus y and La sub 2 minus x Sr sub x CuO sub 4
- Division of Molecular Engineering, Kyoto University, Yoshida, Kyoto 606 (JP)
- Department of Physics, The University of Tokyo, Hongo, Tokyo 113, (Japan)
- Engineering Research Institute, The University of Tokyo, Hongo, Tokyo 113, (Japan)
Detailed analyses of Cu {ital K}-edge x-ray-absorption near-edge structure (XANES) of electron-doped and hole-doped Cu-based oxides with several Ce/Sr substitution rates, Nd{sub 2{minus}{ital x}}Ce{sub {ital x}}CuO{sub 4{minus}{ital y}} and La{sub 2{minus}{ital x}}Sr{sub {ital x}}CuO{sub 4} have revealed that each Ce/Sr substitution has an effect on {similar to}4--5 Cu sites and that an additional electron or hole supplied with the substitution is distributed mainly to {similar to}4--5 (CuO{sub 2}) units, yielding impurity (localized) states.'' When {ital x}=0.15 the impurity states'' amount to {similar to}60--75 % of the whole (CuO{sub 2}) units; the interaction and superposition among the localized states are caused to produce bands like Fermi-liquid states. The substitution causes substantial and a little change in the XANES spectra of Nd-Ce-Cu-O and La-Sr-Cu-O, respectively. This means that the electron doping takes place mainly at the Cu site of (CuO{sub 2}) in Nd-Ce-Cu-O and that the hole doping in La-Sr-Cu-O takes place mainly at the oxygen site. In the unreduced'' Nd-Ce-Cu-O samples no monovalent species but rather divalent species with relatively large 3{ital d}{sup 10} contributions are found. In the reduced'' and superconducting Nd-Ce-Cu-O sample ({ital x}=0.15), Cu{sub 2}O-like monovalent species are found but probably correspond to segregated impurity phases. The essential effect of the reduction to induce the superconductivity in Nd-Ce-Cu-O ({ital x}{similar to}0.15) has not yet been revealed.
- OSTI ID:
- 6910352
- Journal Information:
- Physical Review, B: Condensed Matter; (USA), Journal Name: Physical Review, B: Condensed Matter; (USA) Vol. 41:1; ISSN PRBMD; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
656100 -- Condensed Matter Physics-- Superconductivity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION SPECTRA
ALKALINE EARTH METAL COMPOUNDS
BAND THEORY
CALCIUM COMPOUNDS
CALCIUM OXIDES
CERIUM COMPOUNDS
CERIUM OXIDES
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTRONIC STRUCTURE
HOLES
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
MINERALS
NEODYMIUM COMPOUNDS
NEODYMIUM OXIDES
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PEROVSKITE
PEROVSKITES
PHYSICAL PROPERTIES
QUANTITY RATIO
RARE EARTH COMPOUNDS
SEGREGATION
SPECTRA
STRONTIUM COMPOUNDS
STRONTIUM OXIDES
SUBSTOICHIOMETRY
SUPERCONDUCTIVITY
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
VALENCE
X-RAY SPECTRA