The shear wave magnetoacoustic effect in potassium

Transverse sound waves, in the frequency range 50 to 90 Mc/s, have been propagated through single crystal samples of potassium at 4°K, and the magnetoacoustic effects observed with the magnetic field applied in directions perpendicular (up to 35 kG) and parallel (up to 60 kG) to the propagation direction. For the perpendicular field case, good agreement with the free-electron model was obtained. For propagation along the field, the attenuation and rotation of polarization of linearly polarized waves propagating along [100] were measured, and observations were also made on a [110] oriented crystal. Within experimental error, the evidence agrees with the free-electron model, phonon–helicon interaction effects having been taken fully into account, and there is no definite support for the spin density wave model for the ground state of potassium.