Highly tunable Gilbert damping in two-dimensional van der Waals ferromagnet Fe3GaTe2: From bilayer to the twisted bilayer

Abstract: Van der Waals ferromagnet Fe3GaTe2 possesses both a high Curie temperature and robust perpendicular magnetic anisotropy, holding promise for practical spintronic applications. In particular, understanding and engineering its Gilbert damping which determines magnetization dynamics are crucial for its applications. Here, we investigate the Gilbert damping of bilayer and the twisted bilayer Fe3GaTe2 through first-principles calculations. For the bilayer Fe3GaTe2, we obtain a quite low Gilbert damping when its magnetization is along the z axis at room temperature. In addition, the bilayer Fe3GaTe2 exhibits a large orientational anisotropy of Gilbert damping when its magnetization is rotated from the magnetic easy axis to the hard one. Such anisotropy is attributed to the distinct band structures caused by the anisotropic spin-orbit coupling. Surprisingly, we find that twisting the bilayer Fe3GaTe2 can effectively reduce the Gilbert damping for the perpendicular magnetization, and enhance the orientational anisotropy of Gilbert damping up to 635% when rotating the magnetization from the magnetic easy axis to the hard one. These findings open up an entirely new avenue for the manipulation of Gilbert damping and its anisotropy in two-dimensional van der Waals ferromagnets.