Glass-like properties observed in low-frequency Raman scattering of mixed fluorite crystals
The low-frequency Raman spectra of(CaF2)1-x(LaF3)x mixed crystals in the concentration range from 0.05 < x < 0.4 have been measured as a function of temperature from 4.2 K to 295 K. Concentration dependent quasi-elastic Raman scattering is found for frequencies below 10 cm-1 for A1g + Eg scattering but not for T2g symmetry scattering. The temperature dependence of Raman intensity suggests that this effect is dominated by scattering from a distribution of two-level systems between 4.2 K and 20 K. The lowest impurity-induced vibrational Boson scattering peak at 82 cm-1 which shifts to higher frequency with increasing dopant concentration, also only appears in A1g + Eg symmetry, indicating that the two different kinds of glass-like excitations in these mixed crystals may have a common origin.
Tu, J., S.A. FitzGerald, J.A. Campbell, and A.J. Sievers. 1996. "Glass-like properties observed in low-frequency Raman scattering of mixed fluorite crystals." Journal of Non-Crystalline Solids 203: 153-158.
Journal of Non-Crystalline Solids
Physics and Astronomy