Spontaneous emergence of Dzyaloshinskii-Moriya interaction via field-cooling-induced interface engineering in 2D ferromagnetic ternary tellurides.

Room-temperature skyrmions in the two-dimensional (2D) van der Waals (vdW) ferromagnet Fe3GaTe2 (FGaT) hold great promise for spintronics. However, the origin of the necessary Dzyaloshinskii-Moriya interaction (DMI) within its centrosymmetric lattice remains elusive. Here, we reveal a spontaneous DMI emergence mechanism driven by field cooling (FC) in FGaT and its analog Fe3GeTe2 (FGeT). We show that the commonly used FC process causes the irreversible precipitation of FeTe2 layers on the FGaT surface. This FeTe2/FGaT heterostructure breaks the inversion symmetry, generating a finite interfacial DMI. This phenomenon extends to analogous FGeT, demonstrating its universality. Notably, a threshold thickness governs effective FeTe2 precipitation and subsequent skyrmion formation. Leveraging these findings, we developed an optothermal technique to deterministically write single skyrmions in FGaT without FC. Our findings provides new insights into DMI origins and skyrmion manipulation in ternary tellurides, paving the way for advanced spintronic applications.