Enhanced Curie temperature of ferromagnetic CrSBr by interfacial coupling with elemental two-dimensional ferroelectrics: triggering a new p–d super-exchange coupling path

Abstract

Owing to their distinctive thickness and physical attributes, two-dimensional (2D) materials have exhibited considerable promise in the field of microelectronic devices. Notably, 2D magnetic materials that maintain long-range magnetic order and can be readily modulated by external fields have garnered substantial attention. However, CrSBr, despite being a 2D van der Waals (vdW) semiconducting magnet with an appropriate band gap and stability in air, faces significant hindrance for practical utilization due to its Curie temperature (T_C) of 146 K. The construction of vdW heterostructures through coupling represents an effective approach to improving the intrinsic properties of 2D materials. In this research, 2D elemental ferroelectric Bi (110), which comprises heavy elements, is selected to construct a vdW heterostructure with a CrSBr monolayer. The difference in work function results in interfacial charge transfer from the Bi layer to the CrSBr layer. The CrSBr/Bi heterostructure demonstrates ferromagnetic semiconductor characteristics, exhibiting significant interface orbital coupling between Bi-p and Cr-d. Additionally, it introduces a new super-exchange pathway, Cr–Bi–Cr, to the intrinsic Cr–S/Br–Cr, which increases the T_C to 340 K. The CrSBr/Bi heterostructure possesses robust perpendicular magnetic anisotropy without destroying the ferroelectric behavior of the Bi layer (−0.026 × 10⁻¹⁰ C m⁻¹). These results provide a new design platform and research ideas for the development and application of room-temperature spintronic devices.