Magnetodielectric coupling in a Ru-based 6H-perovskite, Ba$_3$NdRu$_2$O$_9$

Tathamay Basu (1) , Alain Pautrat (1) , Vincent Hardy (1) , Alois Loidl (2) , Stephan Krohns (2)

1 CRISMAT - Laboratoire de cristallographie et sciences des matériaux
2 UNIA - University of Augsburg

A large spin-orbit coupling is a way to control strong magnetodielectric (MD) coupling in higher d-orbital materials. However, reports are rare on such compounds due to often leaky conductive behavior. Here, we demonstrate MD coupling in a Ru-based 6H-perovskite system,Ba$_3$NdRu$_2$O$_9$. The rare-earth ion in a 6H-perovskite makes the system insulating enough to carry out MD investigation. The compound is ferromagnetically ordered below 24 K (TC), followed by another magnetic feature at $T$ ∼17 K ($T_2$). The dielectric constant clearly traces the magnetic ordering, manifesting a peak at the onset of $T_C$, which is suppressed by the application of an external magnetic field (H). The results indicate the presence of MD coupling in this compound, which is further confirmed by the H-dependence of the dielectric constant. Interestingly, a cross-over of the sign of MD coupling is observed at $T$ ∼ $T_2$. We conclude that two different mechanisms control the MD coupling, which yields positive and negative coupling, respectively. Both mechanisms are competing as a function of temperature and magnetic field. This brings us a step closer to design and control the magnetodielectric effect in 6H-perovskites containing higher d-orbital elements.

Domaines: Physique [physics]

Tathamay Basu, Alain Pautrat, Vincent Hardy, Alois Loidl, Stephan Krohns. Magnetodielectric coupling in a Ru-based 6H-perovskite, Ba$_3$NdRu$_2$O$_9$. Applied Physics Letters, 2018, 113 (4), pp.042902. ⟨10.1063/1.5034449⟩. ⟨hal-02161175⟩