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

AMX 3 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, T C = 8.5(1) K) and CsCo(NCS) 3 ( T C = 6.7(1) K) order as weak ferromagnets. On the other hand, CsMn(NCS) 3 orders as an antiferromagnet (Néel temperature, T N = 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.