Magnetic Structure of Ba₂CaCo₂Si₆O₁₇ with Zigzag Spin Chains of Co²⁺ in High Spin‐3/2 State

The magnetic properties and crystal chemistry of the novel Ba 2 CaCo 2 Si 6 O 17 compound exhibiting one‐dimensional zigzag chains of Co 2+ ions ( S = 3/2) are investigated using powder X‐ray diffraction (PXRD), scanning lectron microscopy, energy dispersive‐Xray spectroscopy, and temperature and field‐dependent magnetic measurements. The refinement of PXRD data suggests a Cmcm space group in orthorhombic symmetry for Ba 2 CaCo 2 Si 6 O 17 compound, consisting of a CoO 4 tetrahedral network including 1‐D zigzag Co 2+ chains. Microstructural and elemental analysis substantiate the proper stoichiometry of the synthesized material. Magnetic measurements show paramagnetic characteristics at room temperature, followed by a transition from paramagnetic to antiferromagnetic (AFM) ordering near 17 K, superimposed with weak ferromagnetic ordering (WFM) characteristics. Magnetic hysteresis ( M – H ) at 5 K depicts a sigmoid curve with unsaturated magnetization even at high fields. The negative Weiss temperature value ≈−98 K substantiates the strong antiferromagnetic exchange interaction with a frustration index of ≈5.76. The effective paramagnetic moment is 3.34 μ B , close to the spin‐only value 3.87 μ B of Co 2+ ( S = 3/2). The competing and short‐range FM‐AFM interaction is observed because of the zigzag Co 2+ chain in the compound. The onset of WFM is attributed to the zigzag magnetic chain‐induced lattice and spin distortion in Ba 2 CaCo 2 Si 6 O 17 compound.