First-principles study of ferromagnetic metal Fe₅GeTe₂

For next-generation flexible spin devices, it is crucial to discover and study novel high Tc two-dimensional (2D) magnetic materials considering their atomic-level thickness and flexural mechanical characteristics. Here, we investigated physical properties of a recently rediscovered ferromagnetic 2D material, Fe₅GeTe₂, which has near-room temperature Tc, such as stability of monolayer, and electronic and magnetic properties as well as their changes under strain using DFT method. We found that monolayer formation energy of Fe₅GeTe₂ lies inside the energy range of other 2D materials, and thus successful synthesis of the monolayer is expected. Band structures and density of states (DOS) calculations reveal that monolayer Fe₅GeTe₂ is metallic and of Stoner-type ferromagnet. Besides, we checked the strain effect on its magnetic properties. The ferromagnetic (FM) coupling is quite robust under biaxial strain and enhanced significantly with the increase of Fe magnetic moment from 1.65 μ_B to 2.66 μ_B while the strain increases from zero to +15%. Such a tunable magnetism of Fe₅GeTe₂ could provide an extra advantage for flexible magnetic device applications.