Acoustic Faraday effect in Tb${}_3$Ga${}_5$O${}_{12}$

Abstract

The transverse acoustic wave propagating along the [100] axis of the cubic Tb${}_3$Ga${}_5$O${}_{12}$ (acoustic $c_{44}$ mode) is doubly degenerate. A magnetic field applied in the direction of propagation lifts this degeneracy and leads to the rotation of the polarization vector - the magneto-acoustic Faraday rotation. Here, we report on the observation and analysis of the magneto-acoustic Faraday-effect in Tb${}_3$Ga${}_5$O${}_{12}$ in static and pulsed magnetic fields. We present also a theoretical model based on magnetoelastic coupling of 4$f$ electrons to both, acoustic and optical phonons and an effective coupling between them. This model explains the observed linear frequency dependence of the Faraday rotation angle.