ULTRASONIC STUDY OF DISLOCATIONS IN Cs1

Abstract- The ultrasonic velocity and the attenuation in Cs1 change sensitively with plastic deformation and they recover by y-irradiation. In the amplitude independent region, the measured results of the temperature and frequency dependencesof the change of velocity and the decrement due to dislocations are consistently accounted for by the superposition of the dislocation resonance damping and the relaxation loss of Bordoni type. The extensible string model of dislocations established by Granato and ~ücke /1/ usually accounts well for the ultrasonic behavior of plastically deformed metals in which electron drag is the main source of dislocation damping. As for ionic crystals, in which electron drag is absent, the ultrasonic study of NaCl by Hikat