Attenuation of ultrasonic shear waves in copper at low temperatures

The attenuation and rotation of the plane of polarization of ultrasonic shear waves propagating parallel to a strong magnetic field have been measured in copper single crystals. For sound propagation along [100] and for the case when ql≃1 the results agreed quite well with the predictions for the free electron model. For propagation along [110] and [111] only the magnitude of the zero field attenuation agreed with the simple theory. Measurements for the [111] orientation were complicated through strong internal conical refractions of the sound waves. Results for a [100] oriented crystal with a measured resistance ratio of about 20 000 showed an absorption edge near 19 kgauss, as well as a number of attenuation peaks at lower fields. The existence of an absorption edge at that field as well as some of the attenuation peaks are not at present understood in terms of the Fermi surface for copper.