Tunable valley polarization and magnetic anisotropy by polarization reversal in a Ni2Cl3I3/AgBiP2S6 heterojunction†

Two-dimensional (2D) Janus trihalides have great potential applications in spintronics. In this work, the valley polarization of AgBiP₂S₆ at the K′ and K points is modulated by Ni₂Cl₃I₃, a new 2D Janus trihalide. The Ni₂Cl₃I₃/AgBiP₂S₆ heterojunction exhibits three different electronic properties: metallic, half-metallic, and semiconducting under different stacking configurations. The Ni₂Cl₃I₃/AgBiP₂S₆ heterojunction shows in-plane magnetic anisotropy in model-5 in upward polarization and out-of-plane magnetic anisotropy in model-2 in downward polarization. The Ni₂Cl₃I₃/AgBiP₂S₆ heterojunction exhibits a pronounced band-gap of 434 meV with model-2 in downward polarization. When spin–orbit coupling is considered, valley polarization occurs in the Ni₂Cl₃I₃/AgBiP₂S₆ heterojunction with a value of 19.3 meV. The band-gap, valley polarization and magnetic anisotropy energy of the system can be tuned by biaxial strain. When biaxial strains from −6% to +6% are applied, the valley polarization values of Ni₂Cl₃I₃/AgBiP₂S₆ can vary from 16.2 meV to 19.8 meV. Meanwhile, both the band-gap and magnetic anisotropy energy of the Ni₂Cl₃I₃/AgBiP₂S₆ heterojunction will also be modulated by biaxial strain. The heterojunction has a wide range of applications in the fields of spintronic, optoelectronic, and valleytronic devices, accompanied by the modulation of multiple properties of the system under biaxial strain.