Chemical Control of Magnetic Ordering in Hybrid Fe–Cl Layered Double Perovskites

Recent discoveries of novel physics in two-dimensional (2D) magnetic materials have sparked the search of new layered magnetic semiconductors. Compared to the traditional inorganic 2D van der Waals crystals, hybrid organic–inorganic metal–halide frameworks offer significantly enhanced chemical and structural versatility, where their optical, electronic, and magnetic properties can be readily modulated with both organic and inorganic components. Here, we reported a series of new Fe–Cl-based layered double perovskites LnMIMIIICl8, [n = 4, L = phenylethylammonium or chiral R-(+)-β-methylphenethylammonium and n = 2, L = 1,4-butanediammonium; MI = Ag/Na; MIII = Fe/In]. UV–vis measurements show that their optical band gaps are highly tunable by varying the organic cations, MI ion, and MIII ion. Magnetic susceptibility measurements suggest an antiferromagnetic coupling between the nearest FeIII–FeIII, where the Curie–Weiss temperature, Néel temperature, and frustration factors can be easily modulated with their compositions and dimensionality. Our study demonstrates the rich and interesting magnetic properties in these layered transition-metal–halide double perovskites and paves the way for design of multifunctional magnetic materials.