A Series of Chiral, Polar, Homospin Topological Ferrimagnets: M₃(OOCH)₅Cl(OH₂) (M = Fe, Co, Ni)

An isostructural series of transition metal-formate-chloride-hydrate compounds, M3(OOCH)5Cl­(OH2) (M = Fe, Co, Ni), have been synthesized using a solvothermal method. These compounds crystallize in the chiral and polar space group P31 and are comprised of three different types of helical chains of edge-sharing M2+-centered octahedra. All three compounds undergo 3D ferrimagnetic ordering at low temperature, and the iron and cobalt analogues exhibit field-induced metamagnetic transitions. The magnetic structure was determined by neutron powder diffraction, revealing ferromagnetic intrachain coupling and antiferromagnetic interchain interactions, with the three chains arranged in a two-up/one-down triangular lattice. As all three chains contain one type of metal in the same spin state, these compounds are rare examples of homospin topological ferrimagnets.