Spin-phonon coupling in multiferroic RCrO$_3$ (R-Y, Lu, Gd, Eu, Sm): A Raman study

TL;DR

This Raman study investigates spin-phonon coupling in multiferroic RCrO₃ compounds, revealing that magnetic rare-earth ions influence phonon behavior at magnetic transition temperatures, which may be linked to electric polarization.

Contribution

The paper provides experimental evidence of spin-phonon coupling in RCrO₃ compounds with magnetic R-ions, highlighting the role of 4f-3d interactions in multiferroicity.

Findings

Anomalies in phonon frequencies at TN suggest magnetostriction effects.

Linewidth anomalies at TN indicate spin-phonon coupling in magnetic R-ion compounds.

Low frequency mode anomalies imply R-ion motion influences multiferroic behavior.

Abstract

Raman study on a select few orthochromites, RCrO$_3$ (R = Y, Lu, Gd, Eu and Sm) shows that the phonon behavior at TN in compounds with magnetic R-ion (Gd and Sm) is remarkably different from that of non-magnetic R-ion (Y, Lu and Eu). While anomalies in most of the observed phonon frequencies in all these compounds may result from the distortion of CrO$_6$ octahedra due to size effect and magnetostriction arising from Cr-ordering, the anomalous behavior of their linewidths observed at TN for the compounds with only magnetic R-ion suggests spin-phonon coupling. The presence of spin-phonon coupling and the anomalies in the low frequency modes related to R-ion motion in orthochromites (R = Gd and Sm) support the suggestion that the coupling between 4f-3d moments play important role in inducing switchable electric polarization.