Strain-tuning of perpendicular magnetic anisotropy and valley topological phase transition in the SVNH monolayer†

As a novel dimension in the realm of scientific inquiry, the exploration, manipulation, and effective utilization of the valley have garnered significant attention. In this research, we utilize first-principles calculations to anticipate a novel Janus monolayer, SVNH, which demonstrates good stability at room temperature. Additionally, we delve into the influence of biaxial strain on both the valley characteristics and magnetic behaviors of the material. This research indicates that the magnetic anisotropy of SVNH is primarily induced by the coupling between the d_xy and d_x²–y² orbitals of the V atoms. As the biaxial strain intensifies, the magnetic easy axis undergoes a transition from an in-plane (IP) to an out-of-plane (OP) orientation. Additionally, with further enhancement of the strain, the sequential closing of the −K valley and the K valley leads to the occurrence of topological phase transitions, which are related to the orbital inversions between d_xy + d_x²–y² and d_z² orbitals. Our research has enriched the two-dimensional ferrovalley (FV) family, holding significant implications for the design and application of valley-dependent materials.