Strain-induced ferromagnetism and magneto-electric coupling in two-dimensional ferroelectric ZnIn2S4

Two-dimensional (2D) multiferroic materials are currently in high demand due to their significant potential for applications in the field of high-density data storage devices. However, due to the different requirements for generating ferroelectricity and magnetism, 2D multiferroic materials are rare. In this study, we propose that applying strain can induce magnetism in 2D ferroelectric materials with special electronic structures, thereby creating 2D multiferroics. Taking 2D ZnIn2S4 as an example, it shows robust ferroelectricity with an appropriate switching barrier (79.3 meV), and the out-of-plane ferroelectric polarization is 0.0322 C/m2. Applying biaxial tensile strain can change the energy of the flatband near the Fermi level, ultimately resulting in self-doping phenomena and leading to Stoner-type itinerant ferromagnetism. The reversal of ferroelectric polarization in ZnIn2S4 bilayer and ZnIn2S4–In2Se3 heterostructure can manipulate the magnetic moment of the system, exhibiting significant magnetoelectric coupling phenomena. Our findings provide a pathway for designing 2D ferromagnetic and multiferroic materials.