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. Fe3GaTe2 is a room temperature van der Waals ferromagnet, which, despite having a centrosymmetric crystal structure, has both a large Dzyaloshinskii-Moriya interaction and hosts topological spin textures. Here, Xia, Luo, Malik and coauthors unravel this mystery, showing the critical role of field cooling in the breaking of inversion symmetry in Fe3GaTe2.