The electrical control of magnetic and electronic properties remains a key challenge in the development of next-generation low-power spintronic and optoelectronic devices. Two-dimensional (2D) materials provide an ideal platform for this purpose, as their reduced dimensionality enhances interfacial effects and enables the engineering of novel functionalities through van der Waals heterostructures [1-2]. In these systems, band alignment plays a central role, as it governs charge transfer, carrier separation and recombination dynamics, and ultimately determines the efficiency of optoelectronic and photovoltaic processes [3]. Achieving reversible control of band alignment via ferroelectric polarization would enable non-volatile electrical tunability of interfacial electronic properties. In particular, combining 2D magnetic and ferroelectric layers offers a promising strategy to tailor magnetic stability and band alignment through interfacial strain, charge redistribution, and built-in electric fields [4].

Among 2D ferroelectrics, In₂Se₃ has emerged as a particularly attractive candidate due to its robust room-temperature ferroelectricity, sizable intrinsic polarization field, and nonvolatile bistable polarization that can be reversed at relatively low voltages [5,6]. The large built-in electric field generated at In₂Se₃-based interfaces provides an efficient and experimentally viable route to engineer charge transfer and electronic reconstruction when combined with 2D magnetic materials. Understanding how such polarization fields influence magnetic stability and band alignment at the interface is therefore essential for the rational design of multifunctional heterostructures.

In this work, we explore, by means of first-principles calculations based on density functional theory, the structural, electronic, and magnetic properties of a CrI₂ monolayer and its interaction with a ferroelectric monolayer of In₂Se₃. We analyse how the strain induced at the interface stabilizes a Néel-type antiferromagnetic configuration, which is absent in the isolated CrI₂ monolayer. We further examine the influence of the In₂Se₃ polarization on magnetism and the interfacial charge transfer. Our results show that when the ferroelectric polarization of the In₂Se₃ is reversed, the band alignment of CrI₂/In₂Se₃ switches from a straddling (type I) to a staggered (type II) configuration, and the band gap changes from an indirect gap (0.89 eV) to a direct gap (0.65 eV). These findings reveal a polarization-switchable band alignment mechanism, positioning the CrI₂/In₂Se₃ heterostructure as a promising candidate for multifunctional spintronic and optoelectronic applications.