Soft-mode behavior of electromagnons in multiferroic manganite

TL;DR

This study investigates the soft-mode behavior of electromagnons in multiferroic DyMnO3, revealing magnetic field-dependent frequency softening and its impact on dielectric properties, with insights into domain wall contributions.

Contribution

It provides new experimental evidence of electromagnon softening in multiferroic manganites under magnetic fields, linking it to classical soft mode behavior and dielectric response.

Findings

Electromagnon frequency softens under magnetic field parallel to the a-axis.

Softening correlates with increased static dielectric permittivity.

Domain wall motion influences dielectric behavior when magnetic field is perpendicular.

Abstract

The behavior of the low-frequency electromagnon in multiferroic DyMnO3 has been investigated in external magnetic fields and in a magnetically ordered state. Significant softening of the electromagnon frequency is observed for external magnetic fields parallel to the a-axis (BIIa), revealing a number of similarities to a classical soft mode behavior known for ferroelectric phase transitions. The softening of the electromagnon yields an increase of the static dielectric permittivity which follows a similar dependence as predicted by the Lyddane-Sachs-Teller relation. Within the geometry BIIb the increase of the electromagnon intensity does not correspond to the softening of the eigenfrequency. In this case the increase of the static dielectric permittivity seem to be governed by the motion of the domain walls.