Complex magnetic behavior of the Co²⁺ triangular (saw-tooth) 1D chains in CsCo₂(MoO₄)₂(OH)

Low-dimensional magnetic materials have drawn continued attention in condensed-matter physics for their electronic and magnetic anisotropic properties. In particular, the oxyanion-based systems, with transition-metal (M) oxide sublattices that are magnetically isolated by closed-shell nonmagnetic oxyanions (SiO₄⁻⁴, PO₃⁻⁴, AsO₃⁻⁴), show great potential for diverse magnetic phenomena. We synthesize CsCo₂(MoO₄)₂(OH) single crystals, find the crystal structure, and characterize thermodynamic properties. CsCo(MoO₄)₂(OH) belongs to a rare class of compounds named delta-chain (or sawtooth) type structure, with corner-sharing isosceles triangles whose vertices consist of one Co(1) and two Co(2) atoms. The magnetic susceptibility result reveals long-range ordering below 5 K with a strong anisotropy. The isothermal magnetization data shown a stepwise magnetization when the magnetic field is along the Co-O-Co (saw-tooth chain) direction, with two metamagnetic transitions at 0.3 kOe and 40 kOe. The magnetic structure consists of ferrimagnetic chains which are antiferromagnetically coupled with each other, seen in neutron diffraction.