Spontaneous Enhancement of Dzyaloshinskii-Moriya Interaction via Field-Cooling-Induced Interface Engineering in 2D Ferromagnetic ternary Tellurides

The emergence of two-dimensional (2D) van der Waals (vdW) ferromagnets has opened new avenues for exploring topological spin textures and their applications in next-generation spintronics. Among these materials, Fe3GaTe2 (FGaT) emerges as a model system due to its room-temperature skyrmion phases, which are stabilized by strong Dzyaloshinskii-Moriya interaction (DMI). However, the atomistic origins of DMI in centrosymmetric vdW lattices remain elusive. Here, we report a spontaneous DMI enhancement mechanism driven by field cooling (FC) in FGaT and its analog Fe3GeTe2 (FGeT). Combining Raman spectroscopy and scanning transmission electron microscopy (STEM), we reveal that the commonly used FC process causes the irreversible precipitation of FeTe2 thin layers at the surfaces of the annealed FGaT. The resulted FeTe2/FGaT heterostructure breaks the inversion symmetry and significantly enhances the DMI. Similar phenomenon has been observed in the family ferromagnetic material FGeT as well, indicating the universality of this mechanism. Additionally, we note there is a threshold thickness of FGaT for the effective precipitation of FeTe2 and further formation of skyrmions. Based on our new findings and to further demonstrate the application potential of FGaT in future spintronics, we successfully develop a facile technique to write and pattern single skyrmions in FGaT at room temperature and without FC process. The discovery provide new insights into the mechanisms behind the origin of the DMI and manipulation of skyrmions in ternary tellurides, paving the way for advanced spintronic applications.