Surface-acoustic-wave propagation in paramagnets

Abstract

We have investigated propagation of surface-acoustic waves SAW in the paramagnetic phases of Ce${\mathrm{Al}}_{2}$ and SmSb. The temperature dependence of the SAW velocity is well accounted for with a magnetoelastic coupling of the strain components to the crystal-field-split magnetic ions. In Ce${\mathrm{Al}}_{2}$ we found large magnetic field effects on the Rayleigh wave velocity at 4.3 K which can be qualitatively explained by the same magnetoelastic coupling. Contributions to the SAW velocities from rotationally invariant magnetoelastic interactions could be determined. In Ce${\mathrm{Al}}_{2}$ we found evidence for the magnetoacoustic analog of the Cotton-Mouton-Voigt effect for the SAW. It manifests itself as an amplitude modulated interference effect which we can qualitatively account for. This is the first time Rayleigh waves have been used to investigate the various analogous magnetoelastic effects known from previous acoustic bulk wave experiments.