Antiperovskite Chalco-Halides Ba(3)(FeS(4))Cl, Ba(3)(FeS(4))Br, and Ba(3)(FeSe(4))Br with Spin Super-Super Exchange

Perovskite-related materials have received increasing attention for their broad applications in photovoltaic solar cells and information technology due to their unique electrical and magnetic properties. Here we report three new antiperovskite chalco-halides: Ba(3)(FeS(4))Cl, Ba(3)(FeS(4))Br, and Ba(3)(FeSe(4))Br. All of them were found to be good solar light absorbers. Remarkably, although the shortest Fe-Fe distance exceeds 6 Å, an unexpected anti-ferromagnetic phase transition near 100 K was observed in their magnetic susceptibility measurement. The corresponding complex magnetic structures were resolved by neutron diffraction experiments as well as investigated by first-principles electronic structure calculations. The spin-spin coupling between two neighboring Fe atoms along the b axis, which is realized by the Fe-S···S-Fe super-super exchange mechanism, was found to be responsible for this magnetic phase transition.