A reentrant novel phase is observed in the hexagonal ferroelectric ${\mathrm{H}\mathrm{o}\mathrm{M}\mathrm{n}\mathrm{O}}_3$ in the presence of magnetic fields in the temperature range defined by a plateau of the dielectric constant anomaly. The plateau evolves with fields from a narrow dielectric peak at the Mn-spin rotation transition at 32.8 K in zero field. The anomaly appears both as a function of temperature and as a function of magnetic field without detectable hysteresis. This is attributed to the indirect coupling between the ferroelectric (FE) and antiferromagnetic (AFM) orders, arising from an FE-AFM domain wall effect.

• Received 15 October 2003

DOI:https://doi.org/10.1103/PhysRevLett.92.087204