Controllable spin current in van der Waals ferromagnet Fe_{3}GeTe_{2}

Abstract

The control of spin current is pivotal for spintronic applications, especially for spin-orbit torque devices. The spin Hall effect is a prevalent method to generate spin current. However, it is difficult to manipulate its spin polarization in a nonmagnet. Recently, the discovery of spin current in ferromagnets offers an opportunity to realize the manipulation. In the present Letter, the spin current in the van der Waals ferromagnet Fe_{3}GeTe_{2} (FGT) with varying magnetization is theoretically investigated. It has been observed that the spin current in FGT presents a nonlinear behavior with respect to magnetization. In-plane and out-of-plane spin polarizations emerge simultaneously, and the bilayer FGT can even exhibit arbitrary polarization owing to the reduced symmetry. More intriguingly, the correlation between the anomalous Hall effect and spin anomalous Hall effect has been interpreted from the aspect of Berry curvature and spin. This work illustrates that the interplay of magnetism and symmetry can effectively control the magnitude and polarization of the spin current, providing a practical method to realize exotic spin-orbit torques.