Antiferromagnetic to Ferromagnetic Coupling Crossover in Hybrid Nickel Chain Perovskites

We synthesize and characterize the magnetic and thermody-namic properties of the quasi one-dimensional organic-inorganic hybrid ANiCl3 compounds [A = N(CH3)4+, CH3NH3+, (CH3)2NH2+, C(NH2)3+, and CH(NH2)2+]. Additionally, the crystal structure of (CH3)2NH2NiCl3 is reported. These materials possess chains of face-sharing NiCl6 octahedra in a triangular array. The chains run in one direction and are separated from one another by organic cations of different sizes and geometries. In accordance with the 90 degrees superexchange model, we find that the nature of the magnetic coupling within chains can be predicted by the value of the Ni-Cl-Ni angle. As the Ni-Cl-Ni angle decreases from 90 degrees, the magnetic interactions become increasingly antiferromagnetic. These findings provide a foundation for predicting the magnetic properties of quasi one-dimensional organic- inorganic hybrid ANiCl3 compounds.