Structure driven magnetic correlations and magnetodielectric coupling in 6H-perovskite Ba₃DyRu₂O₉

The 6H-perovskites Ba₃(R/M)Ru₂O₉(R= rare Earth,M= transition metal) exhibit complex magnetism and have been extensively studied recently for their magnetodielectric (MD) properties. Here, we present a detailed study of structural, magnetic, thermodynamic and MD properties of a 6H-perovskite Ba₃DyRu₂O₉. This compound is found to undergo long range antiferromagnetic ordering below ∼5.8 K (T_N), along with the presence of metamagnetic transition at low temperatures. The heat capacity shows two additional anomalies at ∼28 K (T₁) and ∼33 K (T₂), besides the anomaly atT_N. Signature of these anomalies is also visible in the derivative of magnetization curve. The dielectric response also shows weak anomalies aroundT₁andT₂at zero field whereas anomaly atT₂gets suppressed at 80 kOe. The observed MD coupling of ∼2%-4% at 80 kOe field below ∼30 K temperature range, is among the highest values observed for the compounds of this family. Low temperature crystal structures of the compound show sharp distortion of Ru₂O₉octahedra nearT₂. Our study points toward the emergence of structurally driven spin correlations of Ru moments resulting in the observed MD coupling in this compound.