Acoustic Faraday effect in Tb₃Ga₅O₁₂

The transverse acoustic wave propagating along the [100] axis of the cubic Tb₃Ga₅O₁₂ (acoustic c₄₄ 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 magnetoacoustic Faraday rotation. Here, we report on the observation and analysis of the magnetoacoustic Faraday effect in Tb₃Ga₅O₁₂ in static and pulsed magnetic fields. We present also a theoretical model based on magnetoelastic coupling of 4f 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.