Proton magnetic relaxation in lanthanum hydrides
Journal Article
·
· Sov. Phys. - Solid State (Engl. Transl.); (United States)
OSTI ID:6979118
The pulse NMR method at 16 MHZ was used to investigate proton magnetic relaxation in lanthanum hydrides LaH/sub 2.08plus-or-minus0.03/ and LaH/sub 2.98plus-or-minus0.03/, whose compositions were on opposite sides of a metal--semiconductor transition. The investigation was carried out in the temperature range from -180/sup 0/C to +400/sup 0/C. An analysis of the temperature dependences of the spin--lattice T/sub 1/ and spin--spin T/sub 2/ proton relaxation times established that the main contribution to the relaxation in these hydrides was made by modulation of the dipole--dipole interactions as a result of hopping diffusion of hydrogen. A considerable contribution was also made by the interaction of protons with conduction electrons. In the case of LaH/sub 2.08/ the product T/sub 1e/T was 74 +- 5 sec./sup 0/K, which was typical of metallic conduction. In the LaH/sub 2.98/ case the interaction of protons with electrons did not obey the Korringa relationship but was described by the equation T/sub 1e/ =C (1/T: 1/T/sub c/)/sup 1/2/ (where C=2.3x10/sup -2/ sec/sup 0/K/sup 1/2/ and T/sub c/=650/sup 0/K) and obeyed a law typical of semiconductors but with a correction for T/sub c/. The results supported the anion model of lanthanum trihydride, which (together with the proton model) explained well the transition of lanthanum hydride to the semiconductor state when the hydrogen/metal ratio reached H/Me=3.
- Research Organization:
- Physicotechnical Institute, Kazan Branch of the Academy of Sciences of the USSR, Kazan
- OSTI ID:
- 6979118
- Journal Information:
- Sov. Phys. - Solid State (Engl. Transl.); (United States), Journal Name: Sov. Phys. - Solid State (Engl. Transl.); (United States) Vol. 20:1; ISSN SPSSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
HIGH TEMPERATURE
HYDRIDES
HYDROGEN COMPOUNDS
LANTHANUM COMPOUNDS
LANTHANUM HYDRIDES
LOW TEMPERATURE
MAGNETIC RESONANCE
MEDIUM TEMPERATURE
NUCLEAR MAGNETIC RESONANCE
RARE EARTH COMPOUNDS
RELAXATION
RESONANCE
SPIN-LATTICE RELAXATION
SPIN-SPIN RELAXATION
TEMPERATURE DEPENDENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
HIGH TEMPERATURE
HYDRIDES
HYDROGEN COMPOUNDS
LANTHANUM COMPOUNDS
LANTHANUM HYDRIDES
LOW TEMPERATURE
MAGNETIC RESONANCE
MEDIUM TEMPERATURE
NUCLEAR MAGNETIC RESONANCE
RARE EARTH COMPOUNDS
RELAXATION
RESONANCE
SPIN-LATTICE RELAXATION
SPIN-SPIN RELAXATION
TEMPERATURE DEPENDENCE