A microscopic understanding of the magnetism in Fe3GeTe2 with mono-atomic vacancies

Fe3GeTe2 (FGT) is a promising two-dimensional van der Waals magnet known for its metallic conductivity and relatively high Curie temperature (Tc). Structural defects, particularly mono-atomic vacancies, are inevitably introduced in FGT during material fabrication and have been observed to significantly modulate Tc and coercivity. However, the underlying mechanisms of these modifications require systematic exploration. In this work, by first-principles calculations, we investigate the effect of various mono-atomic vacancies on the magnetic properties of FGT. We find that magnetic anisotropy is reduced by all kinds of vacancies by a local density approximation method, and the main reason is the diminished contributions from Te atoms, which possess strong spin–orbital coupling. Furthermore, by examining the vacancy-induced changes in the magnetic exchange coupling (MEC), a deeper understanding of magnetism in FGT can be achieved. For instance, the enhanced MEC among the Fe1up–Fe1up pair by Te vacancies confirms the competition between superexchange coupling and Ruderman–Kittel–Kasuya–Yosida interactions. These insights are instrumental for guiding future applications of FGT.