Large magneto-optical effect and magnetic anisotropy energy in two-dimensional metallic ferromagnet Fe₃GeTe₂

The discovery of ferromagnetic (FM) metal Fe₃GeTe₂ has opened up opportunities for studying two-dimensional (2D) magnetism, such as tunable Curie temperature and anomalous Hall effect. In this work, we study the magnetic anisotropy energy (MAE) and magneto-optical (MO) effects of multilayers and bulk Fe₃GeTe₂ based on first principle calculations. Firstly, all considered Fe₃GeTe₂ structures favor the out-of-plane magnetization with large MAEs of ~3.0 meV/f.u., being ~6 times larger than that of 2D FM semiconductors CrI₃. This is attributed to the dominant Te p_x,y density of states near the Fermi level. Secondly, 2D and bulk Fe₃GeTe₂ also exhibit strong MO effects with their Kerr and Faraday rotation angles being larger than that of best-known MO materials such as Y₃Fe₅O₁₂. The MO spectra are almost thickness-independent, indicating weak interlayer coupling. The MO conductivity spectra are analysed via the dipole selection rule at the Γ, K and K' points, which further reveal that odd layer-number Fe₃GeTe₂ films would exhibit anomalous ferrovalley Hall effect. All these interesting findings thus suggest that 2D and bulk ferromagnetic Fe₃GeTe₂ are promising materials for high density MO and spintronic nanodevices.