ZERO-SOUND ATTENUATION IN ROTATING AND STATIONARY HE-3-A AND HE-3-B

We report on measurements of zero-sound attenuation in rotating and stationary He-3-A and He-3-B, in magnetic fields up to 350 mT. Strong and highly nonlinear rotation speed dependencies of sound amplitudes have been observed in both phases. The data gives information on vortex types and core sizes, although the analysis is not straightforward. The anomalous attenuation in He-3-B at 200 mT near the AB transition, both in the stationary and in the rotating state, is interpreted to arise from the distortion of the energy gap of the B phase. Excess attenuation during the AB phase change was observed. Evidence for soft vortex cores in He-3-B is presented. In addition, a critical velocity in the vortex free state, related to a textural transition, and the vortex creation times have been measured in He-3-B. Furthermore, a metastable structure, possibly a new vortex state, has been observed in He-3-B by rotating the sample through the A --> B transition.