Ferroelectricity at the N\'eel Temperature of Chromium in Rare-earth Orthochromites: Interplay of Rare-earth and Cr Magnetism

TL;DR

This study reveals that certain rare-earth orthochromites exhibit ferroelectricity below the chromium Nél temperature, driven by weak ferromagnetism and magnetic interactions, with potential implications for magnetoelectric applications.

Contribution

It demonstrates the emergence of ferroelectricity in RCrO3 due to the interplay of rare-earth and chromium magnetism, highlighting the role of weak ferromagnetism and magnetic field reversal.

Findings

Ferroelectricity appears below the Nél temperature in magnetic RCrO3.

Ferroelectric polarization is reversed by changing magnetic field polarity.

Ferroelectricity disappears at the spin-reorientation transition in ErCrO3.

Abstract

We report ferroelectricity with fairly large spontaneous polarization (P ~ 0.2 - 0.8 \muC/cm2) below the N\'eel temperature of chromium (TNCr) in weakly ferromagnetic rare-earth orthochromites, RCrO3 (R=rare-earth) only when the rare-earth ion is magnetic. Intriguingly, the ferroelectricity in ErCrO3 (TC = 133 K) disappears at a spin-reorientation (Morin) transition (TSR ~ 22 K) below which the weak ferromagnetism associated with the Cr-sublattice also disappears, demonstrating the crucial role of weak ferromagnetism in inducing ferroelectricity. Further, the ferroelectric polarization (P) could be reversed by reversing the spontaneous magnetization (M) by changing the polarity of magnetic field, indicating a strong magnetoelectric effect. We suggest that the ferroelectricity occurs in RCrO3, due to the combined effect of poling field that breaks the symmetry and the exchange field on R-ion from Cr-sublattice stabilizes the polar state. We propose that a similar mechanism could work in the isostructural rare-earth orthoferrites, RFeO3 as well.