Elastic anomalies and orientational glass transition in Na(CN)xCl1-x mixed crystals. A Brillouin spectroscopic study
Fachrichtung Experimentalphysik 10.2, Universität des Saarlandes, Bau 38,
Postfach 151150, 66041 Saarbrücken, Germany
Revised: 3 June 1999
Published online: 15 February 2000
High performance Brillouin spectroscopy (BS) has been used to study the elastic properties (static and dynamic) of the orientational glassy state of Na(CN)xCl samples ). The temperature behaviour of the elastic properties reveals a more complex scenario for the orientational glass transition than generally believed. The shear elastic constant shows the well-known anomaly, indicated by a minimum, found in other cyanide mixed crystals. The results obtained for the hypersonic attenuation are in clear contradiction with the dynamic character of the -minimum. The temperature behaviour of the longitudinal elastic constant c11 of very dilute Na(CN)xCl samples shows two striking features: i) Similar to the anomalous temperature behaviour of , lowering the temperature first decreases, goes through a minimum and then rises again. The minimum takes place at a temperature above the temperature, , where reaches its minimum value. ii) A kink-like anomaly of is observed at lower temperatures. This second anomaly is similar to the classical one observed in canonical glasses at their glass transition temperature Tg.
PACS: 62.20.Dc – Elasticity, elastic constants / 64.70.Pf – Glass transitions / 78.35.+c – Brillouin and Rayleigh scattering; other light scattering
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2000