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75 As NMR relaxation in glassy Ge–As–Se
Author(s) -
Mammadov Eldar,
Taylor P. Craig,
Reyes Arneil,
Mehdiyeva Salima,
Kuhns Phillip
Publication year - 2010
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.200982797
Subject(s) - nuclear quadrupole resonance , spin–lattice relaxation , relaxation (psychology) , spin–spin relaxation , magnetic dipole–dipole interaction , quadrupole , condensed matter physics , chemistry , coupling constant , nuclear magnetic resonance , exponential decay , glass transition , nuclear magnetic resonance spectroscopy , dipole , materials science , atomic physics , physics , psychology , social psychology , organic chemistry , particle physics , nuclear physics , polymer
We have used high magnetic fields to perform 75 As nuclear magnetic resonance (NMR) relaxation measurements in Ge–As–Se glasses. The spin–lattice relaxation time T 1 has been studied as a function of average coordination number, 〈 r 〉 and temperature, T . We show that the relaxation time constant, T 1 , in this system can be a useful tool to probe rigidity of the glassy matrix. In the two extreme cases, zero‐field nuclear quadrupole resonance (NQR) and high‐field NMR, T 1 exhibits a similar dependence on the average coordination number. Namely, there is a region in this dependence at low 〈 r 〉 values, where the spin–lattice relaxation time does not change remarkably, followed by an increase in T 1 in glasses with 〈 r 〉 more than 2.54. This transition can be correlated with the onset of rigidity percolation in the glassy matrix. The temperature dependence of the spin–lattice relaxation rate is found in the form T 1 −1 ∝ T 2 . This behavior is typical for As and other nuclei in glasses at temperatures below 300 K and is indicative of Raman‐like relaxation mechanism involving low‐frequency modes. Spin‐echo intensity for Ge 2 As 2 Se 5 as a function of pulse separation exhibits exponential decay whose slope is the same as one of the average of the decay found from 75 As NQR measurements. This result indicates to the presence of indirect dipolar coupling of arsenic atoms in this composition.