Strain-Tunable Magnetism and Anisotropy in 2D Fe ₄ GeTe ₂ for Spintronic Applications

The two-dimensional Fe 4 GeTe 2 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 Fe 4 GeTe 2 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 Fe 4 GeTe 2, exhibiting a net magnetic moment of 2.1 μ B /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 Fe 4 GeTe 2 monolayer favors in-plane magnetization, with an MAE of –4.03 meV/unit cell, primarily driven by the d x 2 – y 2 – d xy coupling of Fe1 ions and p z – p y 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 Fe 4 GeTe 2, offering a potential pathway for tuning its properties for 2D spintronics applications.