Non-collinear magnetism in the post-perovskite thiocyanate frameworks CsM(NCS)3

AMX3 compounds are structurally diverse, a notable example being the post-perovskite structure which adopts a two-dimensional framework with corner- and edge-sharing octahedra. Few molecular post-perovskites are known and of these, none have reported magnetic structures. Here we report the synthesis, structure and magnetic properties of molecular post-perovskites: CsNi(NCS)3, a thiocyanate framework, and two new isostructural analogues CsCo(NCS)3 and CsMn(NCS)3. Magnetisation measurements show that all three compounds undergo magnetic order. CsNi(NCS)3 (Curie temperature, TC = 8.5(1) K) and CsCo(NCS)3 (TC = 6.7(1) K) order as weak ferromagnets. On the other hand, CsMn(NCS)3 orders as an antiferromagnet (Néel temperature, TN = 16.8(8) K). Neutron diffraction data of CsNi(NCS)3 and CsMn(NCS)3, show that both are non-collinear magnets. These results suggest molecular frameworks are fruitful ground for realising the spin textures required for the next generation of information technology.