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.