Enhancement of magnetodielectric coupling in 6H-perovskites Ba3RRu2O9 for heavier rare earth cations (R=Ho,Tb)

TL;DR

This study explores how replacing lighter rare-earth ions with heavier ones in Ba3RRu2O9 enhances magnetodielectric coupling, revealing a correlation between R-ion mass and coupling strength, with potential implications for multifunctional materials.

Contribution

It provides the first systematic investigation of magnetodielectric effects in 6H-perovskites with heavier R-ions, demonstrating enhanced coupling linked to larger magnetic moments.

Findings

Magnetodielectric coupling increases with heavier R-ions (Tb, Ho).

Weak magnetic-field induced transition observed at ~30 kOe.

Weak improper ferroelectricity detected in Ho-based compound.

Abstract

The role of rare-earth (R) ions on the magnetodielectric (MD) coupling is always intriguing and markedly different for different systems. Although many reports are available concerning this aspect in frustrated 3d-transition metal oxides, no such reports exist on higher d (4d/5d)-orbital based systems due to the rare availability of highly insulating 4d/5d-systems. Here, we systematically investigated the magnetic, dielectric, ferroelectric and magnetodielectric behavior of the 6H-perovskites Ba3RRu2O9 for different R-ions, namely, R= Sm, Tb and Ho, which magnetically order at 12, 9.5 and 10.2 K respectively. For R=Tb and Ho, the temperature and magnetic-field dependent complex dielectric constant traces the magnetic features, which manifests MD coupling in this system. A weak magnetic-field (H) induced transition is observed for ~30 kOe, which is clearly captured in H-dependent dielectric measurements. No MD coupling is observed for Ba3SmRu2O9. The MD coupling is enhanced by a factor of 3 and 20 times for R=Tb and Ho, respectively, when compared to that of the Nd-counterpart. These results evidence the gradual enhancement of MD coupling with the introduction of heavier R-ions in this series, which is attributed to their larger moment values. A weak improper ferroelectricity is documented for Ho-member, which is absent for Nd. Our investigation establishes dominating 4d(Ru)-4f(R) magnetic correlation in this series for the heavier R-members.