Magnetoelectricity in the system $RAl_3(BO_3)_4$ ($R$ = Tb, Ho, Er, Tm)

TL;DR

This study investigates the magnetoelectric effect in $RAl_3(BO_3)_4$ compounds, revealing a giant polarization in nearly isotropic HoAl_3(BO_3)_4 and highlighting strong coupling between magnetic moments and lattice distortions.

Contribution

It demonstrates a significant magnetoelectric polarization in $RAl_3(BO_3)_4$ compounds, especially in HoAl_3(BO_3)_4, and elucidates the role of magnetic anisotropy and ionic displacements in the effect.

Findings

Giant magnetoelectric polarization of 3600 μC/m^2 in HoAl_3(BO_3)_4

Magnetoelectric effect increases with decreasing magnetic anisotropy

Strong coupling between f-moments and lattice distortions

Abstract

The magnetoelectric effect in the system $RAl_3(BO_3)_4$ ($R$ = Tb, Ho, Er, Tm) is investigated between 3 K and room temperature and at magnetic fields up to 70 kOe. We show a systematic increase of the magnetoelectric effect with decreasing magnetic anisotropy of the rare earth moment. A giant magnetoelectric polarization is found in the magnetically (nearly) isotropic $HoAl_3(BO_3)_4$. The polarization value in transverse field geometry at 70 kOe reaches 3600 $\mu C/m^2$ which is significantly higher than reported values for the field-induced polarization of linear magnetoelectric or even multiferroic compounds. The results indicate a very strong coupling of the f-moments to the lattice. They further indicate the importance of the field-induced ionic displacements in the unit cell resulting in a polar distortion and a change in symmetry on a microscopic scale. The system $RAl_3(BO_3)_4$ could be interesting for the technological utilization of the high-field magnetoelectric effect.