Atomic motion of guest atoms inside semiconducting clathrate cages is considered as an important source for the glasslike thermal behavior.69Ga and 71Ga Nuclear Magnetic Resonance (NMR) studies on type-I Ba8Ga16Sn30 show a clear low temperature relaxation peak attributed to the influence of Ba rattling dynamics on the framework-atom resonance, with a quadrupolar relaxation mechanism as the leading contribution. The data are analyzed using a two-phonon Raman process, according to a recent theory involving localized anharmonic oscillators. Excellent agreement is obtained using this model, with the parameters corresponding to a uniform array of localized oscillators with very large anharmonicity.
@article{arxiv.1511.07615,
title = {NMR relaxation and rattling phonons in type-I Ba8Ga16Sn30 clathrate},
author = {Xiang Zheng and Sergio Y. Rodriguez and Joseph H. Ross,},
journal= {arXiv preprint arXiv:1511.07615},
year = {2015}
}