X-ray-absorption studies of cation ordering and valence in the T sup * -phase La sub 2 minus x minus y R x Sr sub y CuO sub 4 ( R =Sm, Eu, Gd, Tb, and Dy) (US)

Journal Article · Tue Oct 01 00:00:00 EDT 1991 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.44.7008· OSTI ID:5172105

Tan, Z; Budnick, J I; Luo, S; Chen, W Q ^[1]; Cheong, S; Cooper, A S ^[2]; Canfield, P C; Fisk, Z ^[3]

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1. Physics Department and Institute of Materials Science, The University of Connecticut, Storrs, Connecticut (USA)
2. AT T Bell Laboratories, Murray Hill, New Jersey (USA)
3. Los Alamos National Laboratory, Los Alamos, New Mexico (USA)

X-ray-absorption measurements have been made at the lanthanide {ital L} edges, Sr and Cu {ital K} edges in the {ital T}{sup *}-phase La{sub 2{minus}{ital x}{minus}{ital y}R{ital x}}Sr{sub {ital y}}CuO{sub 4} compounds with {ital R}=Sm, Eu, Gd, Tb, and Dy. The La and rare-earth x-ray-absorption near-edge (XANES) data and the extended x-ray-absorption fine-structure data both clearly indicate that the {ital R} and La ions selectively enter the {ital M}{prime} site and {ital M} site, respectively. The degree of this site ordering is nearly perfect and is similar for the Sm, Eu, Gd, Tb, and Dy members of this family. The {ital L}{sub 3} XANES data show that the La, Sm, Eu, Gd, and Dy are trivalent in these compounds, but about 20% of the Tb ions are tetravalent in the Tb material. The Cu {ital K}-edge XANES spectra are consistent with a divalent state for copper, and are essentially identical for the as-prepared nonsuperconducting samples and the high-pressure oxygenated superconducting counterparts. This indirectly suggests that the hole carrier in the {ital T}{sup *}-phase superconductors is largely associated with oxygen atoms as in La{sub 1.85}Sr{sub 0.15}CuO{sub 4}. Based on the results of cation-ordering, cation-valence, and oxygen-content measurements, the superconducting behavior of Sm, Em, and Gd {ital T}{sup *} phases and the lack of superconductivity in the Tb and Dy compounds are discussed.

• DOE Contract Number: AS05-80ER10742; FG02-90ER45424; AC02-76CH00016
• OSTI ID: 5172105
• Journal Information: Physical Review, B: Condensed Matter; (United States), Vol. 44:13; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
COPPER OXIDES
VALENCE
DYSPROSIUM OXIDES
EUROPIUM OXIDES
GADOLINIUM OXIDES
SAMARIUM OXIDES
STRONTIUM OXIDES
TERBIUM OXIDES
ABSORPTION SPECTRA
HIGH-TC SUPERCONDUCTORS
HOLES
STOICHIOMETRY
SUPERCONDUCTIVITY
X-RAY SPECTRA
ALKALINE EARTH METAL COMPOUNDS
CHALCOGENIDES
COPPER COMPOUNDS
DYSPROSIUM COMPOUNDS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
EUROPIUM COMPOUNDS
GADOLINIUM COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RARE EARTH COMPOUNDS
SAMARIUM COMPOUNDS
SPECTRA
STRONTIUM COMPOUNDS
SUPERCONDUCTORS
TERBIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties
656100 - Condensed Matter Physics- Superconductivity