Order-disorder type critical behaviour at the magnetoelectric phase transition in multiferroic DyMnO3
We present the results of detailed dielectric investigations of the relaxation dynamics in DyMnO3 multiferroic manganite. Strong low-frequency relaxation process near the paraelectric-ferroelectric phase transition is observed.
We provide an experimental evidence that this relaxation mode corresponds to a chirality switching of the spin
cycloid in DyMnO3. We demonstrate that the relaxation dynamics is typical for an order-disorder phase transition and may be understood within a simple model with a double well potential.
These results suggest the interpretation of the paraelectric sinusoidal phase in manganites as a dynamical equilibrium of magnetic cycloids with opposite chiralities.