New Magnetoelastic Interaction

We propose a mechanism for the mixing of acoustic magnons and optic phonons propagating along the $c$ axis in terbium observed at 79 K. The interaction involves an intermediate state in which an electron-hole pair is exicted virtually by the phonon and subsequently recombines into a magnon. This interaction becomes possible when the spin-orbit coupling is taken into account, and it also explains the mixing of optic magnons and acoustic phonons as seen in terbium at 200 K and dysprosium at 4.7 K.