Diverse Magnetic Chains in Inorganic Compounds

In both inorganic and metal–organic compounds, transition metals surrounded by ligands form regular or distorted polyhedra, which can be either isolated or interconnected. Distortion of the polyhedron can be caused by the degeneracy in the population of atomic or molecular orbitals, which can be removed by the cooperative Jahn–Teller effect. This effect is often accompanied by the formation of low-dimensional magnetic structures, of which we will consider only chain, or quasi-one-dimensional, magnetic compounds variety. Magnetic chains are formed when transition metal polyhedra bond through a vertex, edge, or face. Moreover, the magnetic entities can be coupled through various nonmagnetic units like NO₃, SiO₄, PnO₃ or PnO₄, ChO₃ or ChO₄, where Pn is the pnictide and Ch is the chalcogen. In most cases, the local environment of the transition metal is represented by oxygen and/or halogens. The prevailing number of chain systems is based on 3d transition metals, albeit 4d and 5d systems attract more and more attention. Mixed 3d–4f single chain magnets became popular objects in metal–organic chemistry.