Electric-field induced magnetic-anisotropy transformation to achieve spontaneous valley polarization

Abstract

Valleytronics has been widely investigated for providing new degrees of freedom to future information coding and processing. Here, it is proposed that valley polarization can be achieved by electric field induced magnetic anisotropy (MA) transformation. Through first-principles calculations, our idea is illustrated by a concrete example of a VSi₂P₄ monolayer. The increasing electric field can induce an in-plane to out-of-plane transition of MA by changing magnetic anisotropy energy (MAE) from a negative to a positive value, which is mainly due to the increasing magnetocrystalline anisotropy (MCA) energy. The out-of-plane magnetization is in favour of spontaneous valley polarization in VSi₂P₄. Within the considered electric field range, VSi₂P₄ is always in the ferromagnetic (FM) ground state. In a certain range of the electric field, the coexistence of semiconductivity and out-of-plane magnetization makes VSi₂P₄ a true ferrovalley (FV) material. The anomalous valley Hall effect (AVHE) can be observed under an in-plane and out-of-plane electrical field in VSi₂P₄. Our studies pave the way in the design of ferrovalley materials using an electric field.