We have carried out an ultrasonic spectroscopy for the single crystals of Sr8Ga16Si30-xGex with x = 0, 15, 20, 24, and 30 in order to investigate cage-size dependence of elastic moduli. We present here the temperature dependence of transverse modulus C44 at various ultrasonic frequencies measured by using a pulse-echo type phase comparison technique. The C44 mode of the sample with x = 30 shows remarkable elastic softening below 100 K. In contrast, no softening is detected in the C44 mode of the samples with x = 0 and 15. We found clear correlation between the off-center motion of guest atoms and the elastic softening.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)