Order-disorder type critical behaviour at the magnetoelectric phase transition in multiferroic DyMnO$_3$

TL;DR

This study investigates the dielectric relaxation dynamics in DyMnO₃, revealing an order-disorder phase transition involving chirality switching of spin cycloids, with implications for understanding multiferroic phase behavior.

Contribution

It provides experimental evidence that the dielectric relaxation mode corresponds to chirality switching, demonstrating an order-disorder transition scenario in DyMnO₃.

Findings

Relaxation process linked to domain wall motion.

Order-disorder transition with short-range cycloidal order above T_C.

Paraelectric sinusoidal phase as a dynamic magnetic equilibrium.

Abstract

We present the results of detailed dielectric investigations of the relaxation dynamics in DyMnO$_3$ multiferroic manganite. Strong low-frequency relaxation process near the paraelectric-ferroelectric phase transition is observed. The high frequency mode is directly to the relaxational motion of multiferroic domain walls. We provide an experimental evidence that this relaxation mode corresponds to a chirality switching of the spin cycloid in DyMnO$_3$. We demonstrate that the relaxation dynamics in DyMnO$_3$ is typical for an order-disorder phase transition and may be understood within a simple model with a double well potential. DyMnO$_3$ follows an order-disorder transition scenario implicating that a short range cycloidal order of Mn-spins exists above $T_C$. These results suggest the interpretation of the paraelectric sinusoidal phase in manganites as a dynamical equilibrium of magnetic cycloids with opposite chiralities.