Spin-splitting and switchable half-metallicity in a van der Waals multiferroic CuBiP₂Se₆/GdClBr heterojunction

Multiferroic van der Waals (vdW) heterojunctions have a strong and nonvolatile magnetoelectric coupling effect, which is of great significance in spintronic devices. The electronic structure and magnetic properties of a GdClBr/CuBiP₂Se₆ vdW multiferroic heterojunction have been calculated using first-principles methods. Due to the spin-up charge transfer and Zeeman field, the ferroelectric CuBiP₂Se₆ exhibits spin splitting at the gamma point. It is found that the electronic structure and magnetic properties of the GdClBr/CuBiP₂Se₆ vdW multiferroic heterojunction have been significantly modulated by the electric polarization of CuBiP₂Se₆. During the reversal of the ferroelectric polarization of CuBiP₂Se₆, the ferromagnetic GdClBr monolayer transforms from a semiconductor to a half-metal. Meanwhile, in both upward and downward ferroelectric polarization, the GdClBr/CuBiP₂Se₆ heterojunction exhibits perpendicular magnetic anisotropy with a Curie temperature of 239 K. As the strain changes from -6% to 6%, the band structure of GdClBr shifts upward, and the band structure of CuBiP₂Se₆ shifts downward. Compressive strain can increase the Curie temperature of the GdClBr/CuBiP₂Se₆ heterojunction. The magnetic anisotropy of heterojunctions highly depends on biaxial strain, where the perpendicular (in-plane) magnetic anisotropy increases with the increased compressive (tensile) strain. The vdW multiferroic GdClBr/CuBiP₂Se₆ heterojunction has potential applications in spintronic devices.