Anomalous ultrasonic attenuation in Bi12GeO20, Bi12SiO20, and Bi12(Ge0.5Si0.5)O20

摘要

In order to study the anomalous ultrasonic attenuation in these compounds, detailed measurements have been performed as a function of temperature, using a variety of frequencies, sound modes, and materials. Their results prove the existence of a selection rule for the interaction mechanism and confirm previous statements of a relaxation process. From symmetry arguments as well as from the observed strong effects of the Ge or Si atoms, respectively, the conclusion was reached that the anomalous attenuation is closely connected to vacancies in the Ge or Si sublattice.