Low temperature dielectric anomalies in HoMnO_3: The complex phase diagram

TL;DR

This study reveals complex low-temperature dielectric anomalies and a intricate phase diagram in HoMnO_3, highlighting multiple magnetic and ferroelectric phase transitions influenced by magnetic fields and lattice interactions.

Contribution

The paper provides a detailed re-evaluation of the T-H phase diagram of HoMnO_3, uncovering reentrant phases, hysteresis, and multicritical points not previously identified.

Findings

Multiple dielectric anomalies at low temperatures

Complex phase diagram with reentrant and hysteretic phases

Magnetoelastic interactions affect lattice and magnetic transitions

Abstract

The dielectric constant of multiferroic hexagonal HoMnO_3 exhibits an unprecedented diversity of anomalies at low temperatures (1.8 K< T <10 K) and under external magnetic fields related to magnetic phase transitions in the coupled system of Ho moments, Mn spins, and ferroelectric polarization. The derived phase diagram is far more complex than previously assumed including reentrant phases, phase transitions with distinct thermal and field hysteresis, as well as several multicritical points. Magnetoelastic interactions introduce lattice anomalies at the magnetic phase transitions. The re-evaluation of the T-H phase diagram of HoMnO_3 is demanded.