Rotational magnetoelastic interactions in the Dzyaloshinskii-Moriya magnet Ba$_2$CuGe$_2$O$_7$

TL;DR

This study investigates the magnetoelastic properties of Ba$_2$CuGe$_2$O$_7$, revealing how magnetic transitions influence elastic modes and uncovering a novel spin-strain coupling linked to Dzyaloshinskii-Moriya interactions.

Contribution

It extends the low-temperature $H-T$ phase diagram and identifies specific elastic modes sensitive to magnetic transitions, highlighting a new spin-strain mechanism.

Findings

Elastic modes are sensitive to magnetic transitions.

Unusual coupling between transverse acoustic mode and cycloidal order.

Evidence of a novel spin-strain mechanism from Dzyaloshinskii-Moriya interaction.

Abstract

We report the magnetoelastic properties of a Ba$_2$CuGe$_2$O$_7$ single crystal at low temperatures under a magnetic field applied along the crystallographic [001] axis. Our results extend to low temperature the $H-T$ phase diagram determined for this compound by neutron scattering. Furthermore, we observe that specific elastic modes are better sensitive to the various magnetic transitions. In particular, we observe an unusual coupling between the in-plane transverse acoustic mode and the cycloidal order at low field, which suggests a novel spin-strain mechanism originating from Dzyaloshinskii-Moriya interaction in this compound.