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 (TN), 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 atTN. 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.