Magnetic and Multiferroic Properties of Two-Dimensional FePX₃ and CuFeP₂X₆ (X = S, Se, and Te)

Two-dimensional (2D) multiferroic materials have significant application potential for novel storage devices due to their tunable magnetic and ferroelectric properties. Transition metal phosphorus chalcogenides MPX 3 (X = S, Se, and Te) were found to be magnetic and multiferroic with excellent tunability, promising for multifunctionalized applications. In this study, we investigated the antiferromagnetic and antiferroelectric properties of two-dimensional FePX 3 and CuFeP 2 X 6 by density functional theory. Monolayer FePS 3 /FePSe 3 and FePTe 3 take intralayer zigzag and Neel antiferromagnetic ground states, respectively. This tunability of intralayer magnetism results from the competition between the spin-exchange interactions of the first and second nearest Fe atoms. Bilayer FePX 3 shows weak interlayer interactions and keeps electronic and magnetic characteristics similar to those of the monolayer. Moreover, by introducing the nonmagnetic Cu atom into FePX 3, the inversion symmetry broken induces CuFeP 2 X 6 to be multiferroic materials. The transition barrier between ferroelectric (FE) and antiferroelectric (AFE) phases in CuFeP 2 S 6 and CuFeP 2 Se 6 is 0.09 and 0.04 eV/f.u., similar to well-known multiferroic CuCrP 2 S 6 . FE-to-AFE phase transition is expected to be achieved by applying an electric field and uniaxial strain. CuFeP 2 Te 6 shows the ground state with a distorted paraelectric phase. Our results show the fundamental properties and in-depth understanding of 2D FePX 3 and CuFeP 2 X 6, guiding further investigation of 2D multifunctionalized magnetoelectric devices.