Stacking Faults and Short‐Range Magnetic Correlations in Single Crystal Y 5 Ru 2 O 12 : A Structure with Ru +4.5 One‐Dimensional Chains

The synthesis, structure, and physical properties of Y 5 Ru 2 O 12 , a new member of the Ln 5 B 2 O 12 class (Ln   = lanthanide, B = Ru, Re, Mo) are reported. Single crystals of Y 5 Ru 2 O 12 are synthesized using a high‐temperature, high‐pressure (700 °C, 200 MPa) hydrothermal method. The structure features edge‐sharing RuORu 1D chains of distorted RuO 6 octahedra. The YO n ( n  = 6 and 7) polyhedral groups bridge RuORu chains across the unit cell by forming a complex 3D structure. The RuORu chains contain alternating shorter and longer RuRu distances along the chain. Single crystal neutron diffraction shows streak‐like diffuse scattering along the H ‐direction, due to stacking faults. Temperature‐dependent anisotropic magnetic measurements reveal a broad feature over a wide temperature range, with a maximum at ≈70 K indicating potential short‐range ordering, with canted antiferromagnetic behavior below 30 K. The dominant magnetic interactions are antiferromagnetic with a large negative Weiss temperature θ  ≈ −200 K. The compound has an effective magnetic moment that is anomalously large for this class of compounds (≈4 μ B  Ru −1 ), and a phenomenological spin Hamiltonian describing the unusual anisotropic magnetization of Y 5 Ru 2 O 12 is proposed.