Field-induced ferroelectric and commensurate spin state in mutiferroic HoMn$_{2}$O$_{5}$

TL;DR

This study reveals that applying a magnetic field to HoMn₂O₅ induces a transition to a commensurate spin state, which is directly linked to the emergence of ferroelectric polarization, highlighting the interplay between magnetic and electric orders.

Contribution

The paper demonstrates that a magnetic field can induce a commensurate spin state in HoMn₂O₅, establishing its crucial role in enabling ferroelectricity in this multiferroic material.

Findings

Magnetic field suppresses the low-temperature incommensurate phase.

Field induces a commensurate magnetic phase at low temperatures.

The commensurate spin state is essential for ferroelectric polarization.

Abstract

Neutron diffraction measurements under high magnetic fields have been performed for the multiferroic compound HoMn$_{2}$O$_{5}$. At zero field, high-temperature incommensurate magnetic (HT-ICM) -- commensurate magnetic (CM) -- low-temperature incommensurate magnetic (LT-ICM) orders occur with decreasing temperature, where ferroelectric polarization arises only in the CM phase. Upon applying a magnetic field, the LT-ICM phase completely disappears and the CM phase is induced at the lowest temperature. This field-induced CM state is completely associated with the field-induced electric polarization in this material [Higashiyama {\it et al}., Phys. Rev. B {\bf 72}, 064421 (2005).], strongly indicating that the commensurate spin state is essential to the ferroelectricity in the multiferroic $R$Mn$_{2}$O$_{5}$ system.