Ab initio study of defect-driven skyrmions in Fe₃GeTe₂

Magnetic van der Waals (vdW) materials offer opportunities to realize atomically thin devices for quantum sensing, spintronics, and related applications. Fe₃GeTe₂ is a well-known example that exhibits nearly room-temperature ferromagnetism with metallicity. Recent scanning tunneling microscopy (STM) experiments have observed the formation of non-collinear spin textures, known as skyrmions, while inelastic neutron scattering has revealed the distribution of exchange couplings between magnetic Fe ions. Despite active research and numerous intriguing findings, it remains unclear how naturally occurring vacancies or defects quantitatively affect the magnetic structures and properties. Here, we calculate the first-principles magnetic Hamiltonian using the magnetic force linear response theory (MFT) combined with the effective defect Hamiltonian method (EDHM), explicitly considering the presence of Fe vacancies. Our calculations reveal doubly enhanced Dzyaloshinskii–Moriya interactions, which drive the formation of skyrmions. We also analyze the spin wave spectrum derived from the obtained defect Hamiltonian. These findings highlight the critical role of defects in complex spin phenomena and providing potential routes for device applications.