Natural ferroelectric order near ambient temperature in HoFeO3: A member of RFeO3 orthoferrites

TL;DR

This study reports the discovery of natural ferroelectric order in HoFeO3 below 210 K, with significant polarization and magnetoelectric coupling, suggesting potential for multiferroic applications and encouraging further exploration of RFeO3 materials.

Contribution

It provides the first evidence of natural ferroelectricity in HoFeO3 near ambient temperature, confirmed by diffraction studies and an exchange striction mechanism.

Findings

Ferroelectric order below 210 K with sizable polarization.

Shift of oxygen atoms causes ferroelectricity.

Strong magnetoelectric coupling observed.

Abstract

Current scenario in multiferroics demands a breakthrough discovery of promising materials after BiFeO3. Recently, the controversial discovery of room temperature ferroelectricity (FE) in SmFeO3 [PRL 107, 117201 (2011); 113, 217203 (2014)] inspires the investigation of HoFeO3. Here, we report a natural ferroelectric order below 210 K (TFE) along c-axis with reasonably large polarization and low-field strong magnetoelectric coupling. Synchrotron and neutron diffraction results confirm that a shift of O atoms along c-axis of polar Pbn21 structure causes FE in HoFeO3. The exchange striction mechanism is suggested to elucidate the ferroelectric order. The results create a renewed attention for searching promising candidates with a natural ferroelectric order and higher TFE in the rest of the RFeO3 series.