Field-Induced Reentrant Novel Phase and a Ferroelectric-Magnetic Order Coupling in HoMnO₃

The reentrant novel phase observed in the hexagonal ferroelectric HoMnO₃ in the presence of magnetic fields in the temperature range defined by a plateau of the dielectric constant anomaly was studied. The plateau was found to evolve with fields from a narrow dielectric peak at the Mn spin rotation transition at 32.8 K in zero field. It was also found that the anomaly appeared both as a function of temperature and magnetic field without detectable hysterisis. It was also found that this anomaly attributed to the indirect coupling between the ferroelectric (FE) and antiferromagnetic (AFM) orders, arising from an FE-AFM domain wall effect.