New Microscopic Mechanism for Secondary Relaxation in Glasses

M. ZURIAGA; L.C. PARDO; P. LUNKENHEIMER; J.LL. TAMARIT; N. VEGLIO; F.J. BERMEJO; A. LOIDL

PHYSICAL REVIEW LETTERS

AMER PHYSICAL SOC

Año: 2009 vol. 103 p. 75701 - 75704

0031-9007

The dynamics of simple molecular systems showing glassy properties has been explored by dielectric spectroscopy and nuclear quadrupole resonance (NQR) on the halogenomethanes CBr2Cl2 and CBrCl3 in their low-temperature monoclinic phases. The dielectric spectra display features which correspond to α- and β-relaxation processes, commonly observed in canonical glass formers. NQR experiments, also performed in the ergodic monoclinic phase of CCl4, enable the determination of the microscopic mechanism underlying the β dynamics in these simple model glasses: Molecules that are nonequivalent with respect to their molecular environment perform reorientational jumps at different time scales. Thus our findings reveal another mechanism that can give rise to typical β-relaxation behavior, raising some doubt about the existence of a universal explanation of this phenomenon.