Heavy Atom Cluster Chains with Strong Spin–Orbit\nCoupling and Magnetic Cations in Mn[PtBi<sub>6</sub>I<sub>12</sub>]

In the search for\nnew magnetic topological insulators with strong\nspin–orbit coupling, by following conceptual considerations\nthat have already proven to be suitable, the bismuth-rich subiodide\nMn[PtBi<sub>6</sub>I<sub>12</sub>] was discovered. Single crystals\nwere grown from mixtures of the elements and BiI<sub>3</sub> using\na temperature program developed on the basis of thermal analyses.\nSingle-crystal X-ray diffraction revealed a rhombohedral structure\nof the cuboctahedral cluster anions [PtBi<sub>6</sub>I<sub>12</sub>]<sup>2–</sup>, which are linked into chains via octahedrally\ncoordinated Mn<sup>2+</sup> cations. Partial substitution of Mn<sup>2+</sup> by Bi<sup>3+</sup> and vacancy formation are responsible\nfor a phase width represented by the general formula (Mn<sub>1–3<i>x</i></sub>Bi<sub>2<i>x</i></sub>)[PtBi<sub>6</sub>I<sub>12</sub>]. Density functional theory-based calculations and\nmeasurements of the electrical resistance showed that the compound\nis a semiconductor with a topologically trivial band gap. Nonstoichiometry\nof chain fragments, corresponding to n- and p-self-doping, strongly\nincreases the conductivity, especially along the chains. The compound\nis paramagnetic at room temperature. Electron spin resonance spectra\nindicate an increase in spin correlations and the buildup of internal\nfields below 30 K.