Spin-lattice relaxation of protons in scandium dihydride

Technical Report · Wed Dec 01 04:00:00 EST 1982

OSTI ID:6578792

Lu, L T

By using pulsed NMR, the spin-lattice relaxation time T/sub 1/ of the protons in ScH/sub x/ (x = 1.73, 1.75, 1.79, 1.83, 1.87, 1.97, 2.02) was measured at 4.2 to 800/sup 0/K to determine the hydrogen locations and interstitial self-diffusion parameters, the electronic structure and the dynamic effect caused by paramagnetic impurities. The fact that the temperature of the (T/sub 1/)/sub min/ increases with hydrogen concentration (H), as well as the fact that no trihydride phase is formed, strongly suggest that negligible O-site occupancy occurs in ScH/sub x/. Analysis of the T/sub 1/ data shows that the activation energy and jump frequency of hydrogen atomic diffusion decrease as H increases. The relaxation rate T/sub 1//sup -1/ in the rigid lattice regime is the sum of the relaxation rate T/sub le//sup -1/ due to conduction electrons and the relaxation rate T/sub 1p//sup -1/ due to residual paramagnetic impurities (< 10 atomic ppM). The Korringa constant T/sub 1e/T increases with H from 304 s-K in ScH/sub 1/ /sub 73/ to 433 s-K in ScH/sub 2/ /sub 02/. Therefore, the conduction electron density of ScH/sub x/ at the Fermi level decreases with H. In the rigid lattice regime, the impurity-contributed relaxation rate T/sub 1p//sup -1/ is mainly caused by very low levels of Gd/sup +3/ ions in our samples; T/sub 1p//sup -1/ is independent of temperature and roughly proportional to the level of Gd impurity. When Gd increases to approx. = 7 ppM, T/sub 1p//sup -1/ increases with decreasing temperature below 100/sup 0/K. Theory suggest that in the rigid lattice regime, /sup 1/H T/sub 1p//sup -1/ is primarily caused by /sup 1/H spin diffusion and that the contribution from the RKKY interaction is negligible. Even with such low levels of Gd impurity, the diffusion-impurity-associated T/sub 1p//sup -1/ is clearly observed. Above the rigid lattice regime, /sup 1/H atommic diffusion may become a second main source for the /sup 1/H diffusion-impurity-associated T/sub 1p//sup -1/.

• Research Organization: Ames Lab., IA (USA)
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 6578792
• Report Number(s): IS-T-1030; ON: DE83004796
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
&amp; Refractories-- Structure &amp; Phase Studies
ACTIVATION ENERGY
BARYONS
COUPLING
DIFFUSION
ELECTRONIC STRUCTURE
ELEMENTARY PARTICLES
ENERGY
FERMIONS
GADOLINIUM COMPOUNDS
HADRONS
HYDRIDES
HYDROGEN COMPOUNDS
IMPURITIES
INTERMEDIATE MASS NUCLEI
ISOTOPES
MAGNETIC RESONANCE
NUCLEAR MAGNETIC RESONANCE
NUCLEI
NUCLEONS
ODD-EVEN NUCLEI
PROTONS
QUANTITY RATIO
RARE EARTH COMPOUNDS
RELAXATION
RESONANCE
RUDERMAN-KITTEL COUPLING
SCANDIUM 45
SCANDIUM COMPOUNDS
SCANDIUM HYDRIDES
SCANDIUM ISOTOPES
SPIN-LATTICE RELAXATION
STABLE ISOTOPES
TEMPERATURE DEPENDENCE
TRANSITION ELEMENT COMPOUNDS