Robust valley polarization induced by super-exchange effects in HfNX (X = Cl, Br, I)/FeCl2 two-dimensional ferrovalley heterostructures

The enthusiasm for predicting the properties of valley materials continues to grow due to the much attention of valley degrees of freedom. In this Letter, a two-dimensional ferromagnetic half-metal 1T-FeCl2 with super-exchange interactions and high Curie temperature is used to construct ferrovalley heterostructures under the means of magnetic proximity effects. The valley polarization up to 47.6 meV can be achieved in the HfNX (X = Cl, Br, I)/FeCl2. Meanwhile, we modulate the valley polarization by changing the interlayer spacing, applying biaxial strain, and changing the magnetization directions. Surprisingly, we find that the super-exchange interactions of the 1T-FeCl2 lead to particular robustness of the valley polarization, so the valley signals in this structure are nonvolatile. Finally, the Berry curvature demonstrates that the HfNI/FeCl2 is capable of achieving the anomalous valley Hall effect. The controllability and the robustness of the valley polarization in HfNX/FeCl2 heterostructure are expected to overcome the volatility of the valley signals, which will be of great help for future applications in spintronics and valleytronics.