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Titolo:
LONGITUDINAL SPIN RELAXATION IN SIMPLE STOCHASTIC-MODELS FOR DISORDERED-SYSTEMS
Autore:
BORGS P; KEHR KW; HEITJANS P;
Indirizzi:
KFA JULICH GMBH,FORSCHUNGSZENTRUM,INST FESTKORPERFORSCH,POSTFACH 1913D-52425 JULICH GERMANY UNIV HANNOVER,INST PHYS CHEM D-30167 HANNOVER GERMANY
Titolo Testata:
Physical review. B, Condensed matter
fascicolo: 9, volume: 52, anno: 1995,
pagine: 6668 - 6683
SICI:
0163-1829(1995)52:9<6668:LSRISS>2.0.ZU;2-1
Fonte:
ISI
Lingua:
ENG
Soggetto:
LATTICE RELAXATION; POSITIVE MUONS; GLASSY STATE; DIFFUSION; NIOBIUM; FIELD; NMR;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
37
Recensione:
Indirizzi per estratti:
Citazione:
P. Borgs et al., "LONGITUDINAL SPIN RELAXATION IN SIMPLE STOCHASTIC-MODELS FOR DISORDERED-SYSTEMS", Physical review. B, Condensed matter, 52(9), 1995, pp. 6668-6683

Abstract

The relaxation of single probe spins was investigated for simple models of systems with quenched disorder. The spin relaxation was calculated for a two-site model with arbitrarily oriented magnetic fields and the result was averaged over various distributions of the fields, and of the hopping rates of the spin. On an intermediate time scale, a modified Kubo-Toyabe behavior is obtained for large hopping rates, in agreement with recent mu SR experiments. A stretched-exponential decay ofthe spin polarization is obtained at longer times. The Kohlrausch exponent is found to be field and hopping-rate dependent, in qualitative agreement with recent NMR and beta-NMR experiments. The resulting longitudinal relaxation rate still does not show the significant deviations from the Bloembergen-Purcell-Pound (BPP) behavior that are typical for glassy systems. Therefore, the random two-frequency model was extended to include time-dependent renewals of the environment. This modification may yield asymmetric peaks for the longitudinal relaxation ratein the BPP plot for very large renewal rates.

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Documento generato il 01/12/20 alle ore 13:11:30