Specific intermediate-valence state of insulating 4f compounds detected by L/sub 3/ x-ray absorption
The intermediate valence of formally tetravalent compounds has been detected by L/sub 3/ x-ray-absorption near-edge structure (XANES) in CeO/sub 2/ and in PrO/sub 2/ but not in UO/sub 2/, which have the same CaF/sub 2/ structure and large f and ligand mixing. The intermediate valence has been found both in CeO/sub 2/ and in Ce(SO/sub 4/)/sub 2/x4H/sub 2/O, which have similar local structure but different crystal structure. We show that L/sub 3/ XANES final states are a direct probe of configuration interaction between 4f/sup n/ and 4f/sup n//sup +1/L configurations in the ground state and that the weight of the 4f/sup n//sup +1/L in the ground state can be deduced. The many-body final states arise from the characteristic properties of these materials: (i) the presence of localized 4f level above the oxygen 2p band separated by a gap deltaepsilon-c with relevant correlation energy U/sub f//sub f/ (U/sub f//sub f/greater than or equal todeltaepsilon-c) and (ii) mixing of 4f localized states with ligand valence orbitals such that the hybridization energy V is of the same order of magnitude as the energy separation ..delta..E between the many-body configuration 4f/sup n/ and 4f/sup n//sup +1/L (Vgreater than or equal to..delta..E). These insulating materials, which cannot be classified as standard mixed-valence systems, are called here interatomic intermediate-valence systems.
- Research Organization:
- Dipartimento di Fisica, Universita-grave-accent degli Studi di Roma ''La Sapienza,'' I-00185 Roma, Italy
- OSTI ID:
- 6883343
- Journal Information:
- Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 35:2; ISSN PRBMD
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
ABSORPTION SPECTRA
ACTINIDE COMPOUNDS
CERIUM COMPOUNDS
CERIUM OXIDES
CERIUM SULFATES
CHALCOGENIDES
ELECTRICAL EQUIPMENT
ELECTRICAL INSULATORS
ELECTRONIC STRUCTURE
EQUIPMENT
HYDRATES
MANY-BODY PROBLEM
OXIDES
OXYGEN COMPOUNDS
PRASEODYMIUM COMPOUNDS
PRASEODYMIUM OXIDES
RARE EARTH COMPOUNDS
SPECTRA
SULFATES
SULFUR COMPOUNDS
URANIUM COMPOUNDS
URANIUM OXIDES
VALENCE
X-RAY SPECTRA