The interaction between sound and helicon waves in potassium

Transverse sound waves have been propagated along strong magnetic fields in single-crystal samples of potassium at 4·2°K. For [100] samples at a frequency of about 200 Mc/s, in a field region above the Kjeldaas absorption edge, oscillations in the received signal were seen : these have been interpreted in terms of a rotation of polarization due to interaction of the sound waves with the helicon modes of propagation. In [110] samples at 49·4 Mc/s, oscillations have also been seen, and have been interpreted in a similar manner.