Novel ultrasonic attenuation peak in ±-PdDx

초록

An unusual ultrasonic attenuation peak has been observed in PdDx. The peak is seen only for longitudinal waves, not transverse waves; and it is observed only in the deuteride, not the hydride. The relaxation strength of the peak increases rapidly with temperature. The data are well described in terms of a simple model involving relaxation of the longitudinal-optical (LO) phonons. The data are fit by an Einstein temperature for the LO phonons, LO=650 K, and a Gr̈neisen constant LO=-3.4. An unusually long phonon relaxation time is found. © 1988 The American Physical Society.