Magnetic damping anisotropy in the two-dimensional van der Waals material Fe3GeTe2 from first principles

Magnetization relaxation in the two-dimensional itinerant ferromagnetic van der Waals material ${\mathrm{Fe}}₃{\mathrm{GeTe}}₂$, below the Curie temperature, is fundamentally important for applications to low-dimensional spintronics devices. We use first-principles scattering theory to calculate the temperature-dependent Gilbert damping for bulk and single-layer ${\mathrm{Fe}}₃{\mathrm{GeTe}}₂$. The calculated damping frequency of bulk ${\mathrm{Fe}}₃{\mathrm{GeTe}}₂$ increases monotonically with temperature because of the dominance of resistivitylike behavior. By contrast, a very weak temperature dependence is found for the damping frequency of a single layer, which is attributed to strong surface scattering in this highly confined geometry. A systematic study of the damping anisotropy reveals that orientational anisotropy is present in both bulk and single-layer ${\mathrm{Fe}}₃{\mathrm{GeTe}}₂$. Rotational anisotropy is significant at low temperatures for both the bulk and a single layer and is gradually diminished by temperature-induced disorder. The rotational anisotropy can be significantly enhanced by up to 430% in gated single- layer ${\mathrm{Fe}}₃{\mathrm{GeTe}}₂$.