Details
| Original language | English |
|---|---|
| Pages (from-to) | 6668-6683 |
| Number of pages | 16 |
| Journal | Physical Review B |
| Volume | 52 |
| Issue number | 9 |
| Publication status | Published - 1995 |
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 SR experiments. A stretched-exponential decay of the 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 -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 rate in the BPP plot for very large renewal rates.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Condensed Matter Physics
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In: Physical Review B, Vol. 52, No. 9, 1995, p. 6668-6683.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Longitudinal spin relaxation in simple stochastic models for disordered systems
AU - Borgs, P.
AU - Kehr, K. W.
AU - Heitjans, P.
PY - 1995
Y1 - 1995
N2 - 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 SR experiments. A stretched-exponential decay of the 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 -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 rate in the BPP plot for very large renewal rates.
AB - 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 SR experiments. A stretched-exponential decay of the 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 -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 rate in the BPP plot for very large renewal rates.
UR - http://www.scopus.com/inward/record.url?scp=4243462060&partnerID=8YFLogxK
U2 - 10.1103/PhysRevB.52.6668
DO - 10.1103/PhysRevB.52.6668
M3 - Article
AN - SCOPUS:4243462060
VL - 52
SP - 6668
EP - 6683
JO - Physical Review B
JF - Physical Review B
SN - 0163-1829
IS - 9
ER -