Multiferroic order parameters in rhombic antiferromagnets. RCrO$_3$

TL;DR

This study investigates the symmetry-based magnetoelectric properties of RCrO3 compounds, revealing their antiferroelectric nature and elucidating the couplings between structural, electric, and magnetic order parameters, explaining experimental polarization behaviors.

Contribution

The paper provides a symmetry analysis of RCrO3, identifying electric dipole arrangements and their couplings with magnetic order, predicting phase transition scenarios and explaining polarization reversal phenomena.

Findings

Electric dipole moments are antiferroelectric in RCrO3.

Couplings between structural, electric, and magnetic order parameters are characterized.

The analysis explains polarization reversal and spin reorientation in RCrO3.

Abstract

In this paper, we explore magneteoelectricity of rare earth orthochromites from the symmetry point of view. We determine the principal structural order parameters and find their couplings with ferroelectric and magnetic orderings. Our calculations showed that electric dipole moments emerge in the vicinity of Cr3+ ions in the unit cell of RCrO3 due to the displacements of oxygen ions from their highly symmetric positions in the parent perovskite phase (structural instability). We find that the electric dipole moments are arranged in an antiferroelectric mode, so, in essence, RCrO3 are antiferroelectric materials. By classifying the order parameters according to the irreducible representations of the RCrO3 symmetry group (D2h16), we determine the possible couplings between distortive, ferroelectric and magnetic orderings and explore the emerging magnetoelectric structures in these terms. Our analysis makes it possible to explain experimentally observed polarization reversal and the concomitant reorientation of spins in a series of RCrO3 compounds and to predict the possible scenarios of phase transitions in RCrO3.