Rare-earth valence and doping in T -, T prime -, and T sup * -phase R sub 2 CuO sub 4 ( R =rare earths)

Journal Article · Fri Jan 31 23:00:00 EST 1992 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.45.2593· OSTI ID:5070943

Tan, Z; Heald, S M ^[1]; Cheong, S; Cooper, A S ^[2]; Budnick, J I ^[3]

---

1. Brookhaven National Laboratory, Upton, New York 11973 (United States)
2. AT T Bell Laboratories, Murray Hill, New Jersey 07974 (United States)
3. Department of Physics, University of Connecticut, Storrs, Connecticut 06269-3046 (United States)

Charge-carrier doping strongly affects the magnetic, transport, and superconducting properties of the {ital T}-, {ital T}{prime}-, and {ital T}{sup *}-phase {ital R}{sub 2}CuO{sub 4} compounds ({ital R}=rare earths). The nature of doping and doping level depend not only on the heterovalent cation substitution and oxygen stoichiometry but also on the rare-earth valence. We have studied the valence of various rare earths in the {ital R}{sub 2}CuO{sub 4} materials using x-ray-absorption spectroscopy. We found that Ce is tetravalent in both {ital T}{prime}-phase Nd{sub 2{minus}{ital x}}Ce{sub {ital x}}CuO{sub 4} and {ital T}{sup *}-phase Pr{sub 2{minus}{ital x}{minus}{ital y}}Ce{sub {ital x}}Sr{sub {ital y}}CuO{sub 4}. Pr is trivalent in the {ital T} and {ital T}{prime} structures. In the {ital T}{sup *} structure, both Pr and Tb have an average valence greater than 3+, very likely arising from an inhomogeneous mixture of trivalent and tetravalent ions, and the latter reside at the eightfold-oxygen-coordinated position. Other rare earths are trivalent in the {ital T}, {ital T}{prime}, and {ital T}{sup *} phases.

• DOE Contract Number: AC02-76CH00016
• OSTI ID: 5070943
• Journal Information: Physical Review, B: Condensed Matter; (United States), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 45:5; ISSN 0163-1829; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
360207 -- Ceramics
Cermets
& Refractories-- Superconducting Properties-- (1992-)
ABSORPTION SPECTROSCOPY
CHARGE CARRIERS
COPPER COMPOUNDS
CUPRATES
ELECTROMAGNETIC RADIATION
ELECTRONIC STRUCTURE
HIGH-TC SUPERCONDUCTORS
IONIZING RADIATIONS
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RADIATIONS
RARE EARTH COMPOUNDS
SPECTROSCOPY
SUPERCONDUCTORS
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
VALENCE
X RADIATION