Solid-State Synthesis Route to a Hybrid Cobalt Chloride Perovskite Ferroelectric

We detail the synthesis and the structural, magnetic, and ferroelectric characterization of two previously unreported hybrid halide compounds—(3-pyrrolinium)CoCl3 and (3-pyrrolinium)FeCl3. These materials crystallize in a hexagonal perovskite-type structure, consisting of face-sharing chains of metal chloride octahedra which are isolated from one another by 3-pyrrolinium rings. Through temperature and field-dependent magnetization measurements, we find that the one-dimensional coupling in the Co compound is antiferromagnetic in nature, and that of the Fe variant appears to result from competing ferromagnetic and antiferromagnetic interactions. (3-pyrrolinium)CoCl3 is found to have a ferroelectric phase with a Curie temperature of 381 K, as corroborated by dielectric constant, polarization, and second harmonic generation measurements. (3-pyrrolinium)FeCl3 also exhibits signatures of ferroelectricity below 358 K, but additional experimental evidence is required to support the transition assignment. Importantly, we report the first Co- and Fe-based organic-inorganic halide perovskite ferroelectrics of the AMX3-type. In doing so, we demonstrate an alternate route to the synthesis of novel hybrid halide materials possessing interesting magnetic or ferroelectric properties.