Coexistence of magnetism and ferroelectricity in the 2D inorganic molecular crystal SbI3•(S7N)3

Two-dimensional inorganic molecular crystals (2D IMCs) represent a novel class of layered materials constructed from inorganic molecules through weak intermolecular interactions. Benefiting from their “LEGO-like” modular assembly nature, we intentionally design a 2D IMC, SbI3•(S7N)3, which exhibits high structural stability, experimental feasibility, and a distinctive breathing kagome-like lattice characteristic. The 2D SbI3•(S7N)3 exhibits the coexistence of an in-plane Y-type noncollinear antiferromagnetic (AFM) ground state and an out-of-plane electric dipole moment. The AFM ordering originates from the N and its neighboring S atoms within the S7N molecule unit, whereas the out-of-plane polarization arises from the intrinsic polarity of the S7N and SbI3 molecules. Due to its P3m1 space group, the intrinsic in-plane dipole moments of the S7N molecules cancel each other exactly. Remarkably, the application of an in-plane electric field can rotate the molecule ordering of S7N rings to break the spatial inversion symmetry, thereby inducing a spontaneous ferroelectric polarization and switching the magnetic ground state from the AFM to ferromagnetic (FM). This work not only identifies 2D IMC SbI3•(S7N)3 as a promising multiferroic material by precisely choosing building blocks, but also advances the exploration of coupled collective orders in 2D IMCs.