Strain-Tunable Magnetism and Anisotropy in 2D Fe₄GeTe₂ for Spintronic Applications

The two-dimensional Fe4GeTe2 monolayer is a metallic ferromagnet with a near-room-temperature transition temperature. Using first-principles calculations, we investigate the impact of uniaxial strain on the mechanical, electronic, and magnetic properties, with a particular focus on the magnetocrystalline anisotropy energy (MAE). Calculations reveal that Fe4GeTe2 retains dynamical, mechanical, and thermodynamic stability across the strain range from –3% to +7%. Additionally, the electronic structure analysis confirms the metallic ferromagnetic nature of Fe4GeTe2, exhibiting a net magnetic moment of 2.1 μB/Fe atom. Strain alters the spin states near the Fermi level. Tensile strain enhances the magnetic moments and the spin polarization, whereas compressive strain suppresses them. We find that the pristine Fe4GeTe2 monolayer favors in-plane magnetization, with an MAE of –4.03 meV/unit cell, primarily driven by the dx2–y2–dxy coupling of Fe1 ions and pz–py interactions in Te. Moreover, the MAE magnitude decreases under tensile strain, with a slight enhancement under compressive uniaxial strain, underscoring its sensitivity to external perturbations. Notably, Te atoms play a significant role in stabilizing the in-plane magnetization, showing further predominance in MAE variations under strain. These findings provide valuable insights into strain-engineered magnetism in Fe4GeTe2, offering a potential pathway for tuning its properties for 2D spintronics applications.