A Field-Induced Re-Entrant Novel Phase and A Ferroelectric-Magnetic Order Coupling in HoMnO3

TL;DR

This study reports a novel re-entrant phase in HoMnO3 induced by magnetic fields, revealing a coupling between ferroelectric and magnetic orders through an antiferromagnetic domain wall mechanism, with observable dielectric anomalies.

Contribution

It uncovers a new field-induced re-entrant phase and elucidates the coupling mechanism between ferroelectric and magnetic orders in HoMnO3.

Findings

Observation of a re-entrant phase in HoMnO3 under magnetic fields.

Dielectric plateau evolves with magnetic field, indicating order coupling.

No hysteresis observed in dielectric anomalies.

Abstract

A re-entrant novel phase has been observed in the hexagonal ferroelectric HoMnO3 in the presence of magnetic fields, in the temperature ranges defined by the plateau of the dielectric constant anomaly. The dielectric plateau evolves with fields from a narrow sharp dielectric peak at the Mn-spin rotation transition at 32.8 K in zero magnetic field. Such a field-induced dielectric plateau anomaly appears both in the temperature sweep at a constant field and in the field sweep at a constant temperature without detectable hysteresis. This is attributed to the indirect coupling between the ferroelectric and antiferromagnetic orders, arising from an antiferromagnetic domain wall effect, where the magnetic order parameter of the Mn subsystem has to change sign across the ferroelectric domain wall in the compound, that influences the ferroelectric domains via a local magnetostrictive effect.