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

TL;DR

This paper reports the observation and analysis of the magneto-acoustic Faraday effect in Tb$_3$Ga$_5$O$_{12}$, demonstrating how magnetic fields lift acoustic mode degeneracy and cause polarization rotation, supported by a theoretical model.

Contribution

It provides the first detailed experimental observation and theoretical explanation of the magneto-acoustic Faraday effect in Tb$_3$Ga$_5$O$_{12}$ using magnetoelastic coupling models.

Findings

Observation of Faraday rotation in Tb$_3$Ga$_5$O$_{12}$

Linear frequency dependence of the rotation angle

Theoretical model explaining the effect

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.