Internal magnetic field effect on magnetoelectricity in orthorhombic $RMnO_3$ crystals

TL;DR

This study explores how the internal magnetic field from 4f moments in orthorhombic RMnO3 crystals influences their magnetoelectric properties, revealing that the 4f moments determine the polarization direction.

Contribution

It demonstrates the role of 4f magnetic moments in controlling ferroelectric polarization direction in RMnO3, highlighting the impact of anisotropic versus isotropic 4f moments.

Findings

Different ferroelectric polarization directions observed in samples with varying 4f moments.

Anisotropic 4f moments influence the polarization along the c axis.

Internal magnetic field from 4f moments determines the polarization direction.

Abstract

We have investigated the role of the 4$f$ moment on the magnetoelectric (ME) effect of orthorhombic $R$MnO$_{3}$ ($R$=rare earth ions). In order to clarify the role of the 4$f$ moment, we prepared three samples: (Eu,Y)MnO$_{3}$ without the 4$f$ moment, TbMnO$_{3}$ with the anisotropic 4$f$ moment, and (Gd,Y)MnO$_{3}$ with the isotropic 4$f$ moment. The ferroelectric behaviors of these samples are different from each other in a zero magnetic field. (Eu,Y)MnO$_{3}$ and (Gd,Y)MnO$_{3}$ show the ferroelectric polarization along the a axis in the ground state, while TbMnO$_{3}$ shows it along the c axis. Such difference may arise from the influence of the anisotropic Tb$^{3+}$ 4$f$ moment. The direction of the ferroelectric polarization of $R$MnO$_{3}$ is determined by the internal magnetic field arising from the 4$f$ moment.