Proton spin-lattice relaxation mechanisms and the metal-insulator transition in cerium hydrides
Nuclear-magnetic-resonance (NMR) experiments have been done on cerium hydride (CeH/sub x/) samples to search for correlations between NMR properties and known electrical conductivity changes as a function of hydrogen concentration and temperature. Data are presented for the /sup 1/H spin-lattice relaxation rate R/sub 1/ ( = 1/T/sub 1/) and some line shapes for 2.10< or =x< or =2.92 for temperatures from about 100 to 375 K. Although two /sup 1/H resonances are observed at some temperatures, proton spin-lattice relaxation is characterized by a single relaxation time at each x and T. To a good approximation R/sub 1/ = A/T+R, where A/T is attributed to direct dipolar coupling between protons and the electronic magnetic dipole moment of Ce/sup 3 +/, and R is an essentially temperature-independent term attributed to indirect (Ruderman-Kittel-Kasuya-Yosida (RKKY)) coupling to the Ce/sup 3 +/ moment. The A/T term is so large that for most experiments the proton-proton dipolar and proton--conduction-electron couplings are negligible. The x dependence of the constant A is consistent with the dipolar coupling. The constant R decreases in a steep manner as x is increased above xroughly-equal2.65 just below the regime 2.75
- Research Organization:
- Soreq Nuclear Research Center, Yavne 70600, Israel
- OSTI ID:
- 5256606
- Journal Information:
- Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 29:1; ISSN PRBMD
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
CERIUM COMPOUNDS
CERIUM HYDRIDES
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
HYDRIDES
HYDROGEN COMPOUNDS
MAGNETIC RESONANCE
NUCLEAR MAGNETIC RESONANCE
PHYSICAL PROPERTIES
QUANTITY RATIO
RARE EARTH COMPOUNDS
RELAXATION
RESONANCE
SPIN-LATTICE RELAXATION
TEMPERATURE DEPENDENCE