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

Domain: biology
Published: 2026-04-02
Editorial outcome: minor_revision

Abstract
Room-temperature skyrmions in the two-dimensional (2D) van der Waals (vdW) ferromagnet
Fe GaTe (FGaT) hold great promise for spintronics. However, the origin of the necessary
3 2
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 Fe GeTe (FGeT). We show that the commonly used FC process causes the irreversible
3 2
precipitation of FeTe layers on the FGaT surface. This FeTe /FGaT heterostructure breaks the
2 2
inversion symmetry, generating a finite interfacial DMI. This phenomenon extends to analogous
FGeT, demonstrating its universality. Notably, a threshold thickness governs effective FeTe
2
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.

Introduction
Since long-range magnetic orders were realized in atomically thin materials, including
ferromagnetism (FM, e.g., CrI and Cr Ge Te 1,2) and antiferromagnetism (AFM, e.g., FePS 3,4),
3 2 2 6 3
more and more two-dimensional (2D) magnets are being investigated by thinning down van der
Waals (vdW) magnetic materials. Plenty of new magnetic properties emerge at the 2D limit, such
as layer-dependent magnetism1,5-7, strong magnetic anisotropy2,8-10, quantum anomalous Hall
effect (QAHE)11,12 and nonlinear topological magnetic structures13-15, offering unprecedented
opportunities for miniaturized spintronic devices. Among these emerging phenomena, magnetic
skyrmions—topologically protected spin textures—have garnered intense interest due to their
potential as information carriers in ultrahigh-density memory and logic architectures15-17.

The formation and stabilization of skyrmions are strongly related to the Dzyaloshinskii-
Moriya interaction (DMI), which arises from broken inversion symmetry and induces chiral spin
textures18-20. Over an extended duration, a proper DMI for generation of skyrmions relies on
growth of chiral magnetic materials14,21 or fabrication of delicately designed heterostructures with
alternative ferromagnetic and heavy-metal films16,22, where cryogenic temperature is still
necessary for the realization of skyrmions23-25.

Recently, room-temperature skyrmions and skyrmion lattice are generated in 2D
ferromagnetic material Fe GaTe (FGaT), whose Curie transition temperature (T ) is around 350-
3 2 C
380 K, by simple field cooling (FC) at moderate temperature26-33. Such breakthrough observations
herald a transformative era in the development of vdW magnets and topological magnetic orders.
However, there persists a fundamental paradox regarding the formation of skyrmions in FGaT:
where does the DMI stem from in such a centrosymmetric crystal structure (P6 /mmc). Recent
3
studies have proposed diverse origins for DMI in FGaT, including Fe vacancies30, atomic
displacement28,29, surface oxidization34,35 and intercalation of Fe atoms32. While these studies
propose miscellaneous hypotheses regarding the origin of DMI, a unified understanding of the
dominant mechanism has yet to emerge.

Apart from the above observations, an unavoidable fact has been largely neglected. To
generate skyrmions in FGaT, thermal treatment during the FC on the sample is unavoidable, and
tellurides, especially ternary compounds, are prone to phase transitions or surface
reconstruction36,37. Therefore, in this study, we investigate the influence of the FC on DMI and
skyrmion formation in FGaTand Fe GeTe (FGeT), revealing the mechanisms of the emergent
3 2
DMI in these materials. By combining the studies of Raman spectroscopy and scanning
transmission electron microscopy (STEM), we reveal that the commonly used FC process causes
the irreversible precipitation of FeTe thin layers at the surfaces of the annealed FGaT. The resulted
2
FeTe /FGaT heterostructure is considered to be the origin of the emergent DMI due to the broken
2
inversion symmetry. Similar phenomenon has been observed in the family ferromagnetic material
FGeT as well, indicating the universality of this mechanism. Additionally, the study explores the
impact of sample thickness on FeTe precipitation and skyrmion formation, indicating FeTe
2 2
precipitation plays a crucial role in triggering the onset of DMI and stabilizing skyrmions. Based
on our new findings and to further demonstrate the application potential of FGaT in future
spintronics, we successfully write and pattern single skyrmions in FGaT by laser excitation at room
temperature and without FC process. This optothermal approach enables deterministic positioning
of individual skyrmions at predefined sites, overcoming previous limitations in skyrmion
manipulation. Our findings not only resolve the paradox of DMI emergence in nominally
symmetric vdW systems but also establish a universal pathway for engineering topological spin
textures through controlled interface engineering in these materials.

Results
Emergence of anomalous Raman signatures in FGaT during field cooling

Pristine FGaT exhibits a vdW layered structure, crystallizing in the P6 /mmc space group, as
3
schematically illustrated in Fig. 1a. Each unit cell consists of a Fe Ga slab sandwiched between
3
two Te layers. Within the Fe Ga sublayer, Fe atoms occupy two distinct Wyckoff positions, with
3
Fe atoms positioned at the top and bottom, and Fe atoms at the center of the slab33. The process
I II
of generating stable skyrmions in FGaT through FC is illustrated in Fig. 1. In its pristine state,
FGaT exhibits a maze-like domain structure with no observable skyrmion formation, as evidenced
by the Magnetic force microscopy (MFM) image shown in Fig. 1b. This observation is consistent
with the strong perpendicular magnetic anisotropy (PMA) of material, which inhibits the formation
of skyrmions under zero-field conditions38. To initiate skyrmion formation, the sample was heated
to 393 K—above its T —to ensure that material entered the paramagnetic phase and was fully
C
demagnetized. Subsequently, the sample was cooled back to room temperature in the presence of
an external magnetic field (~200 Oe). Following the FC process, stable skyrmions were observed
at room temperature by MFM, as demonstrated in Fig. 1c. The skyrmions exhibit an average size
of approximately 100–200 nm, in line with previously reported values30.

A significant challenge during the FC process is the unavoidable increase in temperature,
which could potentially alter the intrinsic properties of the sample. Conventional wisdom posits
that the moderate temperature rise during field cooling exerts negligible impact on the structural
integrity of FGaT. However, the intrinsic thermal sensitivity of ternary tellurides prompts a critical
inquiry: could even mild thermal perturbations during FC trigger irreversible structural
modifications? To address this, a systematic tracking of the lattice dynamics was conducted
through the use of Raman spectroscopy. The Raman spectra, presented in Fig. 1d, reveal notable
changes before and after the FC process. The spectrum in blue corresponds to the pristine FGaT at
303 K, where a broad peak around 150 cm-1 is observed, representing the lattice vibrational modes
of FGaT39. Following FC, two sharp peaks at 121 cm-1 and 140 cm-1 appear in the Raman spectrum
(red line), indicating changes in the FGaTcrystal structure. These peaks persist after undergoing
twice zero-field cooling (ZFC) processes, suggesting irreversible crystal structural changes.
Thermal decomposition of ternary tellurides has been reported to produce Te or FeTe phases
2
under external stimuli such as heating or laser irradiation36,37,40. To identify the origin of two sharp
Raman peaks that appear after field cooling, we performed phonon spectral simulations, which
clearly attribute these peaks to FeTe precipitation. Fig. 1e and 1f show the calculated phonon
2
dispersion relations for FGaT and the orthogonal FeTe , respectively. The calculated phonon
2
modes at Γ point of Brillouin zone, along with their corresponding atomic displacement patterns
and Raman shifts are shown in Fig. S2 and Fig. S3. The corresponding Raman spectra derived
from these simulations are shown in Fig. 1d as black and gray lines for FGaT and FeTe ,
2
respectively. These theoretical spectra exhibit a high degree of correspondence with the
experimental data, suggesting that the two sharp peaks observed in the Raman spectrum are
attributable to the lattice vibrations of FeTe , with the peaks at 121 cm-1 and 140 cm-1
2
corresponding to the A and B Raman modes of FeTe 41.
g 1g 2
To further validate this hypothesis, X-ray photoelectron spectroscopy (XPS) measurements
were performed on FGaT samples at various temperatures. Fig. S4a and S4b show the fine spectra
of Fe 2p in XPS of FGaT at 20 and 160 °C. At 20 °C, the spectrum shows only Fe0 and Fe3+,
consistent with the pristine FGaT phase33. However, the spectrum at 160°C reveals coexistence of
Fe0, Fe2+, and Fe3+, suggesting the presence of both FGaT and FeTe phases, given that the valence
2
states of Fe in FeTe is Fe2+. As demonstrated in Fig. S4c, the proportion of Fe2+ increased
2
gradually with increasing temperature, indicating a temperature-driven precipitation of FeTe .
2
Additionally, for samples that exhibited FeTe Raman signals after annealing, a re-exfoliation
2
process was employed to remove the surface layers and Raman spectroscopy was subsequently
performed on the freshly exfoliated region. The resulting Raman spectra were found to be identical
to those observed in the pristine samples, indicating that the majority of the FeTe precipitation are
2
formed on the surface of FGaT after annealing (Fig. S5).

Surface structural reconstruction and symmetry breaking at FeTe /FGaT interface
2
Second harmonic generation (SHG) is exquisitely sensitive to the loss of inversion symmetry
in crystalline systems, making it a powerful tool for validating interfacial structural changes.To
directly probe the symmetry breaking effects induced by FeTe₂ precipitation, we performed SHG
measurements in Fig. 1g. The SHG signal is absent in pristine FGaT, which can be attributed to its
centrosymmetric crystal structure, belonging to the D point group. However, after annealing, a
6h
subtle SHG signal emerges in the FGaT sample, suggesting a symmetry-breaking effect due to the
structural changes induced by the annealing process. It is noteworthy that the orthogonal FeTe ,
2
which precipitates during the annealing process, belongs to the Pnnm space group (No. 58) and is
classified within the D point group. The crystal structure of FeTe
2h
is also centrosymmetric, and
2
thus, it would not be expected to exhibit an SHG signal. This observation implies that the SHG
signal originates from the interface between the FeTe layer and the underlying FGaT. The
2
precipitation of FeTe
2
during annealing results in an irreversible alteration of the FGaT lattice in
the heterostructure, leading to a breaking of inversion symmetry, which expectedly triggers the
onset of the DMI crucial for stabilizing topological spin textures such as skyrmions.

To further investigate the surface structural reconstruction in the annealed FGaT at atomic
scale, aberration-corrected STEM was employed to examine the crystalline structure of FGaT
nanoflakes, both before and after thermal treatment. High-angle annular dark-field (HAADF)
cross-sectional STEM images of pristine FGaT along the [1 0 0] (Fig. 2a) and [1 2 0] (Fig. 2b)
directions, supported by the bright-field (BF)-STEM image (Fig. S6), reveal atomic lattice without
defects. The crystal structure reveals a Fe Ga slab is intercalated between two tellurium layers,
3
with a vdW gap separating adjacent Te atoms. No intercalation of iron atoms within the vdW gap
is observed. To mitigate ion beam damage during focused ion beam (FIB) sample preparation, a
protective graphene capping layer was applied to the surface layer of FGaT (Fig. S7). The pristine
edge structure of FGaTslab, as shown in the large-area ADF-STEM and BF-STEM images (Fig.
2c, 2d, Fig. S8), remains unchanged, preserving its pristine atomic arrangement.

Upon annealing at 220 °C, atomic rearrangements occur at both the edges of FGaT slab,
resulting in the formation of distinct non-layered structures. These changes are evidenced by the
appearance of additional diffraction spots in the fast Fourier transform (FFT) patterns that do not
correspond to FGaT (Fig. 2e, 2f). The ADF-STEM image in Fig. 2g highlights a vdW gap between
the newly formed non-layered structure and the FGaT layers, similar to the original vdW gap
observed within the FGaT sublayers. To identify the annealed structure, the atomic arrangement
of the non-layered phase was systematically examined along the [1 0 0] and [1 2 0] directions of
FGaT. As shown in Fig. 2h, the ADF-STEM image reveals orthogonal FeTe (Pnnm) along the [0
2
0 1] zone axis, with the lattice spacing of the (2 0 0) plane measured to be 1.97 Å, as confirmed
by the corresponding FFT pattern (Fig. 2i), in excellent agreement with the atomic structure model.
Further analysis of large-scale ADF-STEM images of FeTe
2
reveals diffraction spots (green
square) along the (1 1 3) plane, corresponding to [3 0 1] zone axis (Fig. S9a-9c). The atomic
arrangements along the [3 0 1] direction show a lack of alternating undulations in the tellurium
atoms, unlike those observed along the [0 0 1] direction (Fig. S9d, S9e), as demonstrated by the
detailed ADF-STEM images and FFT patterns of FeTe (Fig. S10). Additionally, the ADF-STEM
2
image along the [1 0 0] direction of FGaT and its FFT pattern confirm that FeTe exists along both
2
the [1 0 0] and [1 0 1] zone axes (Fig. 2j, 2k, Fig. S11). Given the overlapping FFT patterns and
similar atomic structure (Fig. S11), we propose that FeTe forms along both the [1 0 0] and [1 0 1]
2
directions, influenced by the biaxial orientation of FeTe along the [1 2 0] direction of FGaT. The
2
precipitation of FeTe with different crystallographic orientation can be attributed to the thermal
2
annealing process, which represents a non-equilibrium thermodynamic transformation. To verify
the elemental composition of the annealed FGaT, energy-dispersive X-ray spectroscopy (EDS)
was employed, revealing a uniform distribution of Te, Fe, and Ga in the lower region of FGaT (Fig.
2l–2o). Notably, the edge region (area 1) exhibits a significant Te enrichment, with the
corresponding EDS spectra (Fig. 2p) showing an atomic ratio of Fe: Te: Ga = 1: 1.9: 0.28, closely
matching the stoichiometry of FeTe , in perfect agreement with the structural analysis.
2
Furthermore, EDS mapping of area 2 indicates diffusion of Fe atoms into the upper FeTe layer,
2
as reflected in the spectra (Fig. S12), which suggest the formation of an amorphous phase with an
Fe: Te: Ga ratio of 1: 0.19: 0.02. These findings confirm the precipitation of FeTe at the surfaces
2
of FGaT, establishing the FGaT/FeTe
2
heterostructure.

Micromagnetic simulations intuitively validate the interface-induced DMI and its impact on
topological spin textures (Fig. S13 and Fig.S14). For pristine FGaT (D = 0.1 mJ/m2, set to match
centrosymmetric constraints), field-dependent simulations reproduce only maze-like magnetic
domains, aligning with our previous experimental observations42. Conversely, the FeTe
2
/FGaT
interface (D = 2.0 mJ/m2) generates diverse spin textures, including skyrmions, bi-skyrmioniums,
and skyrmion bags which are directly attributable to interfacial DMI. Crucially, simulations
replicate the FC process: Initial maze-like domains (Fig. S14a) transform into skyrmion lattices
after FC under a 300 Oe magnetic field (Fig. S14b), mirroring experimental MFM results (Fig. 1c-
d). These simulation confirm that FeTe /FGaT interface induced DMI emergence fundamentally
2
reconfigures spin textures.

To rule out the possibility that the observed magnetic changes stem from bulk structural
modifications, we performed X-ray diffraction (XRD) measurements. Large scale bulk structural
modification, specifically the self-intercalation of surplus Fe into the van der Waals gaps, is known
to sensitively alter the c-axis lattice parameter43,44. As shown in Fig. S24, the (00l) diffraction peaks
of the FGaT matrix remain sharp and maintain their positions after annealing. Quantitative analysis
reveals that the interplanar spacing remains virtually unchanged (d ≈ 0.85 Å), with a negligible
variation of ~ 0.007 Å. This stability contrasts with the significant lattice distortions (typically >
0.25 Å) observed in self-intercalated phases44, confirming that the bulk crystal structure is well-
preserved. Consequently, the symmetry breaking and emergent DMI are attributed to the
engineered interface rather than bulk intercalation effects.

Universal FeTe precipitation and interface-driven spin texture evolution in FGeT
2
The spontaneous precipitation of FeTe through thermal annealing is not merely a
2
phenomenon isolated to FGaT but represents a universal mechanism within the family of ternary
telluride, attributable to the low bond energy of the compounds. Recent studies have shown that
FGeT, a well-known family member of FGaT, undergoes thermal decomposition upon annealing,
resulting in the precipitation of FeTe and Fe Ge phases through a temperature-induced self-
2 3
decomposition mechanism37. As with FGaT, FeTe
2
precipitation exerts a comparable effect on
FGeT, as illustrated in Fig. 3. The Raman spectrum of pristine FGeT before annealing (Fig. 3a)
exhibits a broad peak near 150 cm-1, which is attributed to the characteristic peak of FGeT, as
previously reported45. Upon annealing, the Raman spectrum of FGeT displays two sharp peaks,
consistent with the results observed in FGaT. These sharp peaks correspond to the characteristic
vibrations of FeTe , indicating that the precipitation of FeTe also occurs in FGeT after thermal
2 2
treatment.

To further investigate the atomic structure and chemical composition of the annealed FGeT,
graphene-capped cross-sectional ADF-STEM imaging and EDS analysis were conducted (Fig.
S15). The pristine cross-sectional FGeT nanosheet exhibits the similar atomic arrangement as
FGaT (Fig. S16) , and the EDS mapping shows a uniform distribution of Fe, Ge, and Te, with an
atomic ratio of Fe: Ge: Te = 3: 1: 2 (Fig. S17). Large-scale ADF-STEM images (Fig. 3b) and their
corresponding FFT pattern (Fig. 3c) confirm the precipitation of FeTe in FGeT following the
2
same annealing process used for FGaT. Detailed ADF-STEM image reveals the interface between
the non-layered FeTe and the FGeT layers (Fig. 3d), which is absent in pristine FGeT (Fig. S18).
2
The thermally annealed FGeT exhibits greater sensitivity to temperature, as evidenced by the
more extensive precipitation of FeTe , with a thickness of up to 10.2 nm (Fig. S19). Moreover, a
2
clearer ADF-STEM image (Fig. 3e) of a distorted hexagonal-shaped FeTe along the [1 0 0] and
2
[1 0 1] directions shows distinct high-contrast (brighter) and low-contrast (darker) spots,
representing Te and Fe atom columns, respectively. The FFT pattern (Fig. 3f) further supports this
interpretation. The lattice arrangement of FeTe along the [1 0 0] direction shows Fe atoms
2
alternating between two adjacent tellurium layers, as confirmed by the intensity line profile (Fig.
3g). However, along the [1 0 1] direction, the Fe atoms are doubly occupied between the tellurium
layers (Fig. 3h), with the periodic intensity variation of Fe atoms resulting from the simultaneous
presence of both [1 0 1] and [1 0 0] directions in the FeTe structure. The ADF-STEM image of
2
FeTe along the [0 0 1] direction (Fig. 3i) reveals alternating undulations of Te atoms, which are
2
corroborated by the absence of characteristic diffraction spots from the [3 0 1] FeTe structure in
2
the corresponding FFT pattern (Fig. 3j).

Additionally, the precipitation of FeTe has been shown to be associated with the formation
2
of skyrmions, as observed through MFM measurements. Fig. S20 and S21 illustrate the formation
of skyrmions under an external magnetic field, both before and after annealing. In pristine FGeT,
only a few isolated skyrmions are observed in the MFM image (Fig. 3k) taken at 150 K under a
0.7 kOe magnetic field. In contrast, highly-densed skyrmion lattice formed in the annealed FGeT,
as evidenced by the MFM image (Fig. 3l) (150 K and 0.7 kOe). This transformation is attributed
to the precipitation of FeTe during the annealing process and resulting FeTe /FGeT
2 2
heterostructure, analogous to the FeTe /FGaT heterostructure, breaks the inversion symmetry and
2
gives rise to a finite interfacial DMI.

Thickness-dependent FeTe precipitation and correlated topological magnetic states
2
The ability to manipulate skyrmion properties, such as size, density, and thermal stability, is
pivotal for their integration into high-density memory and logic devices. However, achieving such
control requires a fundamental understanding of how material parameters, particularly thickness,
influence the underlying mechanisms of skyrmion formation. It has been demonstrated in recent
studies that FGaT with varying thicknesses exhibit distinct skyrmions properties, including size
and order26,30,31. Interestingly, the extant literatures appear to exhibit a thickness limit for
observable skyrmions. The critical thickness limit for the formation of skyrmions may be based
on this FeTe /FGaT heterostructure strategy, as illustrated in Fig. 4. Fig. 4 investigates the
2
temperature dependence of Raman spectra in FGaT with varying thicknesses and threshold for the
precipitation of FeTe . Fig. 4a and 4b display the temperature-dependent Raman spectra for 15 nm
2
and 70 nm thick FGaT samples, respectively. At room temperature (303 K), both samples exhibit
a broad peak around 150 cm-1, characteristic of FGaT, confirming the presence of pure FGaT
before thermal annealing. As the temperature increases, the thicker sample (70 nm) begins to
precipitate FeTe evidenced by a weak signal of A mode (~120 cm-1) of FeTe emerging at 338 K.
2 g 2
By 368 K, the two characteristic FeTe peaks are clearly visible, indicating substantial precipitation.
2
In contrast, the thinner sample (15 nm) shows subtle signal of FeTe peaks only at 373 K, with
2
more pronounced features appearing only at 423 K (Fig. S22). The two samples, differing in
thickness, exhibit a notable disparity in the temperature at which FeTe
2
precipitation occurs.

To further explore the role of thickness and temperature on FeTe precipitation, Raman
2
spectra were collected for samples with thicknesses ranging from 15 to 600 nm. As shown in Fig.
4c, FeTe precipitation exhibits a strong dependence on sample thickness. The transition
2
temperature was defined as the point at which the intensity ratio of FeTe to FGaT Raman peaks
2
exceeds 1/3 (Fig. S22), indicating a certain amount of FeTe precipitation at this temperature. This
2
approach ensures consistent quantification of FeTe
2
precipitation onset across thickness-dependent
datasets. The transition temperature reveals a distinct threshold at approximately 25 nm. For
samples thinner than 25 nm (red dots), the transition temperature ranges from 380–400 K, whereas
thicker samples (orange dots) precipitate FeTe at lower transition temperatures, between 320–350
2
K. This threshold indicates that thicker FGaT samples are more prone to FeTe
2
precipitation, with
a clear distinction in the transition temperatures based on the sample thickness. Furthermore, the
intensity ratio of FeTe to FGaT Raman peaks at the highest temperature (423 K) reinforces this
2
threshold. As shown in Fig. S22b, the ratios for thinner samples range from 1.5 to 2, while for
thicker samples, the ratios increase to 3.5 to 6. This suggests that thinner FGaT samples are less
likely to precipitate FeTe .
2
A comparison with the previous literatures (Fig. 4d) suggests that the observed thickness
threshold for FeTe precipitation closely aligns with the minimum thickness required for skyrmion
2
formation in FGaT, as reported earlier26,30. This further implies that FeTe precipitation plays a
2
critical role in skyrmion formation by providing the necessary symmetry breaking to stabilize
skyrmion lattices.

Optothermal creation of isolated single skyrmions via local phase engineering
The established link between FeTe precipitation and skyrmion stabilization was further
2
developed through the implementation of a laser annealing protocol on FGaT flake, thereby
facilitating the creation of site-specific skyrmions, which are crucial for spintronic applications.
As illustrated schematically in Fig. 5a, the FGaT sample was positioned under an out-of-plane
magnetic field with approximately 200 Oe, aligned with the FC condition. A 532 nm continuous-
wave laser was irradiated in a pre-designed 3×3 array pattern, generating localized thermal
annealing zones while maintaining an inter-spot distance of approximately 5 μm. The laser power
was set to 2.5 mW, which was optimized to be within the safe operating window for FeTe
2
precipitation (see Methods), and the irradiation time for each spot was five minutes. This duration
is sufficient to reach the temperature to induce FeTe precipitation, yet it remains well below the
2
threshold required to cause the degradation of the FGaT. This spatially selective laser annealing
process directly induced the formation of FeTe
2
nanodomains, as confirmed by Raman
spectroscopy. The Raman mapping of characteristic A
g
phonon mode at 121 cm-1 (Fig. 5b)
demonstrates exclusive intensity enhancement at all nine irradiated sites, while exhibiting no
detectable peak at this position in non-annealed regions. This site-specific spectral fingerprint
conclusively demonstrates FeTe
2
formation exclusively within laser-defined zones, with the
surrounding matrix retaining pristine FGaT characteristics. Notably, MFM image of these specific
locations revealed the presence of isolated single skyrmions, which exhibited precise positional
correspondence with the laser-defined sites. Fig. 5c shows a magnetic landscape divided by the
Raman mapping boundary (dashed box). Maze-like domains dominate the unmapped regions and
correspond to predominant ferromagnetic domains. In contrast, the scanned territory exhibits laser-
modified labyrinth-like domains, indicative of the reduced ferromagnetic phase42. Critically, only
the nine sites that were intentionally irradiated and coincided with Raman mapping hotspots
nucleated isolated single skyrmions (with diameters of 300-400 nm) that were confined to laser-
spot dimensions, demonstrating phase-specific magnetic engineering by laser control. These laser-
patterned single-skyrmion arrays enable a room-temperature operation without FC process. Their
deterministic positioning and ambient operational stability overcome persistent scalability barriers
in topological computing architectures. This breakthrough paves the way for implementing energy-
efficient spintronic logic gates with nanoscale resolution, enabling next-generation spintronic
memory and logic devices29,46. Fig. 5d demonstrates a skyrmion-based AND logic gate enabled by
our laser-directed single-skyrmion writing technique, which provides the critical foundation for
programmable topological computing. By leveraging deterministic laser patterning (Fig. 5a-c), we
successfully created individual single-skyrmion in FGaT by laser FC. Binary inputs are encoded
via single-skyrmions core polarization (up/down) defined as logic states “0” for up and “1” for
down with the polarization direction set by external magnetic field orientation during laser FC. As
illustrated in Fig. 5d, the two input skyrmions are created at the top- and bottom-right corners. A
pulse current is utilized to concurrently drive the skyrmions towards the center47,48. Input pairs
aligned in parallel (0–0 or 1–1) undergo coherent merging, preserving the topological
configuration. In contrast, antiparallel input combinations (0–1 or 1–0) result in topological
annihilation, collapsing into a trivial ferromagnetic state. The output is detected via a tunneling
magnetoresistance (TMR) sensor, which registers a logical '1' only detecting a surviving down-
polarized skyrmion. This mechanism enables Boolean AND functionality with zero static power
consumption, showcasing the feasibility of energy-efficient, reconfigurable topological logic
operations.

Methods
Fe
3
GaTe
2
single crystal growth
FGaTcrystals were grown using the self-flux method. Highly pure Fe (99.9 %), Ga (99.99 %),
and Te (99.99 %) powders, with a mole ratio of 1:1:2, were mixed under Ar atmosphere in a glove box
and sealed in a quartz tube under 1.9 Pa. To capture the excess flux during centrifugation, a crucible
filled with quartz wool was placed on top of the growth crucible. The melt was homogenized at 1000 °C
for approximately 24 hours, then cooled quickly to 880 °C in 1 hour, followed by slow cooling to
780 °C in 100 hours. At this temperature, the ampoules were removed from the furnace and placed in
a centrifuge to expel the excess flux. Then large single crystals could be obtained. FGaTnanoflakes
were mechanically exfoliated onto a freshly cleaned SiO2/Si substrate
. In our experiment, the pristine
FGaT nanoflakes were mechanically exfoliated onto a freshly cleaned SiO2/Si substrate with the
thicknesses ranging from 12 to 600 nm (Fig. S1).

Magnetic force microscopy measurements
MFM measurements on FGaT were performed using the DIMENSION ICON (Bruker). The
magnetic field during FC was generated by a neodymium magnet. The measurement was conducted in
a glove box protected by high-purity nitrogen gas at room temperature. The magnetic tip from
Nanoworld coated with Co/Cr was used for all measurements. The force constant and resonance
frequency of this tip are 3 N/m and 75 kHz, respectively. During the measurement, the topography of
the sample was first acquired in tapping mode. During the second scan, the MFM tip was lifted by 100
nm above the sample to measure the magnetic signal in tapping mode. MFM measurements on FGeT
were carried out using variable temperature MFM system (attocube-2100). Hard magnetic point probes
with cobalt coating (Nanosensors) were employed. The samples were cooled from room temperature
to 150 K in a low-pressure helium gas environment under zero magnetic field. Prior to MFM imaging,
a relatively flat region was identified using tapping mode AFM, and slope compensation was
performed to ensure a constant tip-sample distance across the scan area. Phase images were then
acquired at a fixed tip-sample separation, typically set to 100 nm.

Raman Spectroscopy measurements
The Raman measurements were obtained by a Witec Alpha 300R confocal Raman microscope.
The 532 nm linear polarized laser was focused perpendicular to the surface of the sample through a
100x objective lens (numerical aperture = 0.9). The maximum power is kept below 0.2 mW to avoid
the laser thermal effects on the sample. The Raman signals were first collected by a photonic crystal
fiber and then coupled into the spectrometer with 1800 g/mm grating.

HAADF-STEM
STEM specimens were prepared by the focused ion beam (FIB) lift-out technique using the FEI
Helios 5cx system. Atomic resolution STEM images were performed on an aberration-corrected FEI
Themis Z transmission electron microscopy, equipped with a cold field-emission gun operating at 200
kV. The resolution ADF-STEM images were collected with a convergence semiangle of 24.5 mrad,
collecting scattering from >44 mrad. Image filtered using Gaussian functions.

Theoretical calculation
The relaxed crystal structures were obtained using the Vienna Ab initio Simulation Package
(VASP) within the framework of density functional theory (DFT). The exchange-correlation
functional was described using the general gradient approximation (GGA) as parameterized
by Perdew, Burke, and Ernzerhof (PBE). The plane -wave energy cutoff and convergence threshold
were set to 450 eV and 10- 6 eV, respectively. Phonon spectra with a 2×2×2 supercell were
calculated using the finite-displacement method implemented in the Phonopy code.

Micromagnetic simulation
Micromagnetic simulation was carried out with MuMax3 software based on the Landu–
Lifshitz–Gilbert equation. Slab geometries of dimensions 10.2 μm × 10.2 μm × 300 nm were used
for the simulations of magnetic field-driven spin textures evolutions and the generation of zero-
field skyrmions. The following parameters were used in the simulations: saturation magnetization
M = 3 × 105 A/m, Ku = 9 × 104 J/m3, the exchange constant A = 8 × 10−12 A/m, the DMI coefficient
D = 0.1 mJ/m2 for pristine FGaT and 2.0 mJ/m2 for FeTe /FGaT interface, and the damping constant
2
𝛼 = 0.2. An out-of-plane magnetic field of 300 Oe was applied during the FC procedure.

Laser patterning and localized phase engineering
For the deterministic creation of isolated skyrmions via optothermal writing, a continuous‑wave
laser (532 nm) was focused through a 100x objective lens (NA=0.9) onto the surface of the FGaT
flake (thickness > 25 nm). The laser power was set to 2.5 mW, selected within the determined
operating window of 0.5–4 mW (bounded by the phase transition threshold and ablation limit),
and the exposure time for each irradiation spot was fixed at 5 minutes. A pre‑designed 3 × 3 array
pattern was written with an inter‑spot distance of approximately 5 μm. During irradiation, the
sample was held under an out‑of‑plane magnetic field of about 200 Oe. The same optical path was
used for subsequent confocal Raman verification, with the laser power reduced below 0.2 mW to
avoid additional thermal modification during mapping.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "The article describes the origin and applications of skyrmions in the 2D ferromagnetic material Fe3GaTe2 at room temperature. The authors demonstrated a spontaneous formation of FeTe2/Fe3GaTe2 interface during field cooling, which had been overlooked in previous studies. This interface enhances the DMI which is crucial for skyrmion formation and resolves a longstanding issue of the DMI origin in Fe3GaTe2. They further demonstrated the precise generation of single skyrmions via laser-based field cooling. I believe this paper holds significant novelty and importance in both experimental mechanisms and application potential, making it worthy of publication in Nature Communications. However, there are some minor concerns.\n1. The experimental evidence linking the FeTe2/Fe3GaTe2 interface to skyrmions formation is convincing, while the theoretical explain seems a bit sparse. Can you explain more how the FeTe2/Fe3GaTe2 interface affect the DMI enhancement?\n2. SHG is important for studying symmetry. Have you tested angle-resolved polarized SHG? What should the polarization of the FeTe2/Fe3GaTe2 interface be?\n3. The article mentions the universality of FeTe2 precipitation, which might be crucial for surface structures and physics besides DMI and skyrmions. Does this phenomenon occur in other ternary tellurides?\n4. The localized single skyrmions are groundbreaking. The device concept is also intriguing and promising. However, some important articles in this field have not been cited, such as (1) Nature Nanotechnology 16, 1086-1091 (2021) (2) Nature Nanotechnology 12, 123-126 (2017).\n5. There are some grammatical and spelling errors. On page 2, line 21, ‘the discovery provide new insights’ should be ‘the discovery provides new insights’; On page 6, line 11, ‘valance states’ should be ‘valence states’.\nAfter addressing these concerns, I think this article can be published in Nature Communications.", "reviewer_2": "This study focuses on the mechanism of spontaneous enhancement of Dzyaloshinskii-Moriya interaction (DMI) in two-dimensional van der Waals ferromagnets Fe₃GaTe₂ (FGaT) and its analog Fe₃GeTe₂ (FGeT). Above-room-temperature chiral skyrmion lattice and Dzyaloshinskii Moriya interaction in a van der Waals ferromagnet Fe3−xGaTe2 has been reported [Nat. Commun. 15, 4472 (2024)], where the DMI arises from the off-centered FeΙΙ atoms which break the spatial inversion symmetry. It has been also reported that Néel-type skyrmion in WTe2/Fe3GeTe2 van der Waals heterostructure [Nat. Commun. 11, 3860 (2020)]. Here, the authors claim that the inversion asymmetry arising from the irreversible precipitation of FeTe2 at the surface causing the DMI in FGaT(FGeT) system. Obviously, the two reported DMIs are originating from different mechanism even though in the very similar system. The research features a clear logical framework and detailed arguments. Experimentally, multiple characterization methods are employed to verify the viewpoint. The data integrity and logical consistency are reasonable, and the study has high academic value and application potential.\nHowever, there is still room for improvement. It is recommended that the authors revise the manuscript according to the following suggestions, after which consideration may be given to accepting it for publication:\nComment-1: The article indicates that the Dzyaloshinskii-Moriya Interaction (DMI) strength D at the FeTe2/FGaT interface is 2.0 mJ/m2, yet it fails to provide relevant verification for this value. It is suggested to conduct additional experimental and theoretical work to further validate the DMI strength.\nComment-2: The authors have done first-principles calculations for the FGT to verify their experimental results. In page 9, the authors claim that “These computations confirm that FeTe2/FGaT interface induced DMI enhancement fundamentally reconfigures spin textures.” However, they did not give any DMI data from first-principles. I suggest the authors to do first-principles calculations for the DMI strength, following the method Phys. Rev. Lett.115, 267210 (2015); Nat. Rev. Phys. 5, 43 (2023).\nComment-3: It is suggested to add labels for temperature and magnetic field strength to Fig. 1b and Fig. 1c.\nComment-4: The article mentions that the characteristic Raman peaks of FeTe2 still exist under zero field condition, yet relevant data are lacking.", "reviewer_3": "The manuscript by Xia .et.al. deals with the determination of different phases during the annealing process of Fe3GaTe2 and Fe3GeTe2 crystals and its impact on the formation of magnetic textures. The authors provide an extensive characterization to support their claims. While the data clearly points to the formation of a secondary phase (FeTe2) that precipitates in a crystalline way towards the surface, the mechanism of skyrmion formation and claimed “enhancement of DMI interaction” is not well described and understood. In particular, the occurrence of symmetry breaking and induced skyrmion-like magnetic textures can have various origins besides the claimed FGaT/FeTe2 interface , such as self-intercalation, point defects, other magnetic phases, etc. Especially in systems that undergo precipitation, a plethora of changes may occur to the initial crystal phase. It is now well known in the community that TEM data (in which the authors base) is extremely local for a crystal that is macroscopic and not necessarily representative of the sample behaviour. Additional large-scale techniques to rule out the presence of point defects (e.g. Te-deficiency) and self-intercalation of surplus Fe -which can migrate not only to the top, but also to the bottom FGaT layer,- should be employed: for instance X-ray diffraction to resolve the FGaT structure before and after annealing (akin Phys. Rev. Materials 4, 074008 (2020) and Physical Review Letters 133 (25), 256702 (2024)). Additionally, the authors should discuss the influence of second Fe-Ga precipitate phase on the magnetic properties, in particular on the effect on MFM imaging as this phase is concentrated at the surface. This is necessary to unveil the origin of the observed SHG response and skyrmion-like bubble formation which is one of the most important aspects of the paper. The authors should address this main issue in a revised manuscript, as well as several other points:\n1) The Raman-signal in Figure 1 show a full transition from one phase to another, without overlap of the two phases (as it was detected by TEM, Figure 2). The authors should comment if the surface sensitivity of their Raman setup is in line with the observation of only the FeTe2 phase after annealing.\n2) SHG measurements. If the creation of a non-centrosymmetric structure happens only at the interface, it might reflect on a very weak signal. However, if it comes from a rather bulk phenomenon, it should scale with thickness. The authors should perform thickness dependent SHG measurements (samples shown in Figure 4c) to corroborate the origin of the signal.\n3) There is another surface layer which consists of Fe-Ga rich amorphous phase. What is the thickness and influence of this layer on the various measurements? Since it contains Fe, it is probably magnetic. Could you provide magnetization measurements of the crystals before and after annealing? Is this also possible affecting magnetic bubble formation? MFM is surface sensitive so it will actually get stronger signals from the topmost layer.\n4) How do you get the DMI constant of the FeTe2/FGaT interface as D = 2.0 mJ/m2? Can you provide calculation/estimation details?\n5) The title states: “enhancement of DMI”, but there is no direct experimental evidence of DMI enhancement. The magnetic bubble formation is a hint that DMI might be the reason behind, but is very qualitative and does not merit the claim in the title. Even though, it is not clear whether it is a bulk or an interface-driven DMI. Either the authors bring more quantitative evidence or they should tone down the DMI statements in the manuscript.\n6) In the laser-patterning experiment, is it possible to control laser parameters and define the boundaries of FeTe2 formation, similar to the heating study? That would serve as a practical guide for other scientists that may want to reproduce the results.\n7) “The bond-free vdW interfaces in FeTe2/FGaT enable seamless integration of dissimilar materials without lattice-matching constraints, preserving spin coherence for low-1 power spintronic devices.” This sentence is misleading. The preservation of spin coherence is not automatically given at a vdW interface of dissimilar materials."}, "author_response": "Point-to-point response (our responses are marked in blue):\nReviewer #1 (Remarks to the Author):\nThe article describes the origin and applications of skyrmions in the 2D ferromagnetic\nmaterial Fe3GaTe2 at room temperature. The authors demonstrated a spontaneous\nformation of FeTe2/Fe3GaTe2 interface during field cooling, which had been\noverlooked in previous studies. This interface enhances the DMI which is crucial for\nskyrmion formation and resolves a longstanding issue of the DMI origin in Fe3GaTe2.\nThey further demonstrated the precise generation of single skyrmions via laser-based\nfield cooling. I believe this paper holds significant novelty and importance in both\nexperimental mechanisms and application potential, making it worthy of publication in\nNature Communications. However, there are some minor concerns.\nResponse: We are encouraged by the reviewer’s assessment of the novelty and\nimportance of our work. Indeed, exploring interface-induced topological phenomena in\n2D van der Waals ferromagnets is a rapidly evolving and timely frontier. We believe\nour findings offer a critical pathway for engineering DMI in centrosymmetric systems,\naddressing a key challenge in the development of next-generation spintronic devices.\nComment-1: The experimental evidence linking the FeTe2/Fe3GaTe2 interface to\nskyrmions formation is convincing, while the theoretical explain seems a bit sparse.\nCan you explain more how the FeTe2/Fe3GaTe2 interface affect the DMI enhancement?\nResponse to Comment-1: It is gratifying that the reviewer considers our Raman results\nare convincing. We fully recognize the reviewer’s concern about the theoretical\nunderstanding of the interface and its link to DMI. We realize that although we have\npresented a lot of experiment data about the FeTe /Fe GaTe interface and skyrmions\n2 3 2\nformation, the emergence of DMI is not well described. Hnece, we add a discussion\nabout the DMI and skyrmion formation in the revised manuscript (Supplementary Note\n1):\nSupporting Note 1 | Discussion of symmtry breaking, DMI emergence and\nskyrmion formation\nThe Dzyaloshinskii-Moriya interaction (DMI) is an antisymmetric exchange\ncoupling that favours a chiral, non-collinear alignment between neighbouring spins1-4.\nIt is described by the Hamiltonian , where the\nDM\nvector reflects the interplay of spin-orbit coℋuplin=g a𝐃𝐃n𝑖𝑖d𝑖𝑖 ⋅lo(c𝐒𝐒a𝑖𝑖l× st𝐒𝐒ru𝑖𝑖)ctural asymmetry.\nIn a cry𝐃𝐃st𝑖𝑖a𝑖𝑖l with inversion symmetry, for every bond there exists an equivalent\nbond with , leading to complete cancellatio(n\n𝑖𝑖\n, a 𝑗𝑗)nd a vanishing net DMI. In\nour case, the𝐃𝐃 p𝑖𝑖𝑖𝑖ri=sti−ne𝐃𝐃 F𝑖𝑖𝑖𝑖GaT crystallizes in the centrosymmetric space group (P6\n3\n/mmc).\nConsequently, it exhibits no macroscopic DMI. Following FC, the formation of the\nFeTe /FGaT interface in the sample results in the disruption of the global structural\n2\ninversion symmetry, enabling the emergence of a finite, interfacial DMI.\nThe magnetic order and domain configuration in a ferromagnet are determined by\nthe competition between several fundamental energies. Within the continuum theory,\nwhich is appropriate for describing mesoscopic textures like domain walls and\nskyrmions3,5,6, the free energy density is given by:\nex ani dip dmi\nℱ = ℱ +ℱ +ℱ +ℱ\nHere, is the exchange energy density, where\nex\n2 2 2\nis th e eℱxch=an𝐴𝐴g[e( ∇st𝑚𝑚iff 𝑥𝑥 n)es+s. (T∇h𝑚𝑚is 𝑦𝑦 t)erm+ (p∇e𝑚𝑚na 𝑧𝑧 li)ze]s spatial variations in magnetization,\n𝐴𝐴favouring a uniform spin alignment.\nani\nis the uniaxial anisotropy energy\n2\nwhich aligns the magnetization alongℱ the =eas−y𝐾𝐾 (𝑢𝑢o𝑚𝑚ut𝑧𝑧-of-piane) axis, wiht being the\nuniaxial anisotropy constant. is the magnetosta𝐾𝐾ti 𝑢𝑢 c (dipole)\ndip\n1\nenergy density where is the mℱagne=tiz−ati2o𝜇𝜇n 0 v𝐌𝐌ec⋅to𝐇𝐇r 𝑑𝑑 and is the demagnetizing field\ngenerated by itself.𝐌𝐌 This energy drives the formation o𝐇𝐇f m𝑑𝑑agnetic domains to reduce\nstray fields. C𝐌𝐌ritically,\ndmi\nis the Dzyaloshinskii–Moriya interaction (DMI) energy\ndensity. For an interfaceℱ with broken inversion symmetry along the surface normal ( -\naxis), it takes the form7: 𝑧𝑧\ndmi\n∂𝑚𝑚𝑥𝑥 ∂𝑚𝑚𝑧𝑧 ∂𝑚𝑚𝑦𝑦 ∂𝑚𝑚𝑧𝑧\nℱ = 𝐷𝐷𝑚𝑚𝑧𝑧 −𝑚𝑚𝑥𝑥 +𝑚𝑚𝑧𝑧 −𝑚𝑚𝑦𝑦 \nwhere is the DMI consta∂n𝑥𝑥t. This te∂rm𝑥𝑥 is finit∂e 𝑦𝑦only in n∂o𝑦𝑦n-centrosymmetric\nstructures 𝐷𝐷and energetically favors a fixed, chiral rotation between neighbouring spins,\nwhich is the fundamental mechanism that stabilizes Néel-type domain walls and,\nultimately, magnetic skyrmions3,8.\nIn our case, the pristine FGaT with a centrosymmetric structure results in a negligible\nDMI ( ). Consequently, the magnetic state is governed by the competition\ndmi\namong ℱthe re≈m0aining three energy terms. The strong perpendicular magnetic anisotropy\n(PMA) aligns spins uniformly out-of-plane. The magnetostatic energy counteracts this\nby favoring the subdivision of the magnetization into domains of alternating polarity to\nminimize the stray field energy, while the exchange energy penalizes overly sharp\ndomain walls, promoting smooth variations. Crucially, none of these three interactions\nfavours a specific chiral rotation of spins. The balance achieved among them stabilizes\na non-chiral, maze-like (stripe) domain pattern as the magnetic ground state, consistent\nwith our experimental observations (Fig. 1b).\nFollowing FC, the FeTe /FGaT interface intrinsically breaks the global inversion\n2\nsymmetry of the system, giving rise to a finite DMI energy density . Consequently,\ndmi\nthe magnetic energy landscape is fundamentally augmented byℱ this fourth, non-\ncollinear term. While the perpendicular anisotropy continues to align spins out-of-plane\nand the magnetostatic energy still favors domain subdivision, the DMI acts as a chiral\nselector. It energetically favours Néel-type domain walls with a fixed rotational\nhandedness, introducing a macroscopic preference for non-collinear spin arrangements\nthat was absent in the pristine state. When the DMI strength exceeds a critical threshold,\nthe energy gain from forming an array of topological magnetic skyrmions can outweigh\nthe energy cost of their compact morphology compared to the non-chiral maze-like\ndomain phase9,10. The applied magnetic field during the FC process further assists in\nnucleating this ordered state. Therefore, the new ground state under these conditions\nbecomes stable skyrmions (Fig. 1c), directly manifesting the presence and action of the\nemergent interfacial DMI.\nThus, the observation of a transition from a maze-like domains to stable skyrmions\nformation after FC provides direct and intuitive experimental evidence that a significant\nDMI has emerged at the engineered interface. The skyrmions themselves are the\nmacroscopic manifestation of the underlying DMI, marking a transition in the magnetic\nground state driven by symmetry-breaking interfacial engineering.\nWe believe this discussion can clearly explain the relationship between symmetry\nbreaking, DMI, and skyrmion formation, which theoretically explains how DMI\nevolves from zero to finite values after the formation of FeTe /FGaT interface and then\n2\nemergence of skyrmions.\nSummary of revisions following Comment-1: We have added a comprehensive\ntheoretical discussion on the emergence of the interfacial DMI in Supplementary Note\n1 of the Supporting Information.\nComment-2: SHG is important for studying symmetry. Have you tested angle-resolved\npolarized SHG? What should the polarization of the FeTe2/Fe3GaTe2 interface be?\nResponse to Comment-2: We thank the reviewer for raising this insightful question\nregarding the symmetry of the interface, which prompted us to perform the crucial\nangle-resolved polarized SHG measurements. The figure below illustrates a typical\nangle-resolved polarized SHG. The pattern manifests isotropy. Notably, due to optical\ndiffraction limit, the test region is approximately several hundred nanometers in size.\nAs the FeTe precipitation referenced is polycrystalline (Fig. S13), it is conceivable that\n2\nmultiple directions of FeTe /FGaT may have been collected within a single test, thereby\n2\ngiving rise to macroscopically isotropic behavior.\nFig. R1 Angle-resolved polarized SHG in FeTe /FGaT\nbe crucial for surface structures and physics besides DMI and skyrmions. Does this\nphenomenon occur in other ternary tellurides?\nResponse to Comment-3: We thank the reviewer for raising this pertinent and forward-\nlooking question, which underscores the broader relevance of surface reconstruction in\nthe family of ternary tellurides. Indeed, the phenomenon of FeTe precipitation is\n2\nobserved in both FGaT and FGeT, as evidenced by our Raman, STEM, and XPS\nanalyses. As mentioned in the discussion part, its universality is likely rooted in the low\nbonding energy common to many ternary tellurides, which makes them prone to surface\ndecomposition under thermal treatment. In fact, similar two sharp Raman peaks have\nalso been reported in other ternary tellurides such as Cr Ge Te and SnBiTe 11,12, which\n2 2 6 4\nmay be indicative of binary telluride or elemental Te precipitation. This supports the\nnotion that surface precipitation could be a more general characteristic in this material\nfamily.\nComment-4: The localized single skyrmions are groundbreaking. The device concept\nis also intriguing and promising. However, some important articles in this field have\nnot been cited, such as (1) Nature Nanotechnology 16, 1086-1091 (2021) (2) Nature\nNanotechnology 12, 123-126 (2017).\nResponse to Comment-4: We fully recognize the importance of these papers and we\nhave referred them in our revision now (labeled ref. 47, 48 in revised manuscript).\nSummary of revisions following Comment-4: We have cited the important articles\nrecommended by the reviewer in the revised manuscript (Refs. 47 and 48).\nComment-5: There are some grammatical and spelling errors. On page 2, line 21, ‘the\ndiscovery provide new insights’ should be ‘the discovery provides new insights’; On\npage 6, line 11, ‘valance states’ should be ‘valence states’.\nResponse to Comment-5: We would like to express our sincere thanks to the reviewer\nfor their meticulous attention to detail. Both errors have now been rectified in the\nrevised manuscript (Page 2, Line 21 and Page 6, Line 11).\nSummary of revisions following Comment-5: We have corrected the specified\ngrammatical and spelling errors on Page 2, Line 21 and Page 6, Line 11 of the revised\nmanuscript.\nAfter addressing these concerns, I think this article can be published in Nature\nCommunications.\nReviewer #2 (Remarks to the Author):\nThis study focuses on the mechanism of spontaneous enhancement of Dzyaloshinskii-\nMoriya interaction (DMI) in two-dimensional van der Waals ferromagnets Fe₃GaTe₂\n(FGaT) and its analog Fe₃GeTe₂ (FGeT). Above-room-temperature chiral skyrmion\nlattice and Dzyaloshinskii Moriya interaction in a van der Waals ferromagnet\nFe3−xGaTe2 has been reported [Nat. Commun. 15, 4472 (2024)], where the DMI arises\nfrom the off-centered FeΙΙ atoms which break the spatial inversion symmetry. It has\nbeen also reported that Néel-type skyrmion in WTe2/Fe3GeTe2 van der Waals\nheterostructure [Nat. Commun. 11, 3860 (2020)]. Here, the authors claim that the\ninversion asymmetry arising from the irreversible precipitation of FeTe2 at the surface\ncausing the DMI in FGaT(FGeT) system. Obviously, the two reported DMIs are\noriginating from different mechanism even though in the very similar system. The\nresearch features a clear logical framework and detailed arguments. Experimentally,\nmultiple characterization methods are employed to verify the viewpoint. The data\nintegrity and logical consistency are reasonable, and the study has high academic value\nand application potential.\nResponse: We sincerely thank the reviewers for their thoughtful comments and overall\npositive evaluation of our manuscript. Indeed, the strategy of utilizing spontaneous\ninterface engineering to induce DMI in 2D van der Waals ferromagnets represents a\npromising avenue for spintronics. We believe our comprehensive experimental\nvalidation offers essential insights for developing next-generation devices based on\nthese centrosymmetric materials.\nHowever, there is still room for improvement. It is recommended that the authors revise\nthe manuscript according to the following suggestions, after which consideration may\nbe given to accepting it for publication:\nComment-1: The article indicates that the Dzyaloshinskii-Moriya Interaction (DMI)\nstrength D at the FeTe2/FGaT interface is 2.0 mJ/m2, yet it fails to provide relevant\nverification for this value. It is suggested to conduct additional experimental and\ntheoretical work to further validate the DMI strength.\nResponse to Comment-1: We thank the reviewer for this crucial comment regarding\nthe quantification of the DMI strength. The value of D = 2.0 mJ/m2 mentioned in the\noriginal manuscript was an estimated input parameter used in our preliminary\nmicromagnetic simulations to qualitatively demonstrate the feasibility of skyrmion\nformation. By systematically varying DMI strength while using independently\nmeasured material parameters, we found that only when the DMI strength reached\napproximately 2.0 mJ/m2 could the simulations consistently reproduce the experimental\noutcomes: specifically, the field-cooling-driven transition from mazed-like domains to\na stable skyrmion lattice (Fig. S14), as well as the emergence of diverse topological\nspin textures such as skyrmion bags under varying magnetic fields (Fig. S13).\nTo further rigorously validate the DMI strength, we have now performed a\nquantitative analysis of DMI strength based on experimental measurements by using a\nsemi-analytical model (Supplementary Note 2), incorporating the average skyrmion\ndiameter measured from MFM images (Fig. S27) alongside the exchange stiffness (A)\nand anisotropy constant (K ) of FGaT. The resulting DMI constant D ≈ 0.98 mJ/m2\neff\nindicates a strong interfacial interaction. While the simulation parameter implies a\nhigher value to stabilize specific textures in the idealized model, the experimental value\nis of the same order of magnitude and provides direct, quantitative support for our\nconclusion that the FeTe /FGaT interface generates significant DMI sufficient to induce\n2\nskyrmion formation. The detailed calculation procedure is described in Supplementary\nNote 2:\nSupporting Note 2 | Experimental estimation of magnetic parameters and DMI\nconstant\n1. Determ ination of Exchange Stiffness ( )\nTo quantify the exchange interaction, 𝑨𝑨we analyzed the thermal demagnetization\nbehavior of the sample. In the low-temperature regime, the reduction of saturation\nmagnetization M (T) due to spin-wave excitations can be described by the Bloch\nS\n3/2\nlaw13,14:\n𝑇𝑇\n.\n𝑀𝑀𝑠𝑠(𝑇𝑇)\n3/2\n𝑀𝑀𝑠𝑠(0) = 1−𝐵𝐵𝑇𝑇\nHere, M (0) represents the saturation magnetization at 0 K. The coefficient is\nS\nintrinsically linked to the spin-wave stiffness via the following relation𝐵𝐵13:\nspin\n𝐷𝐷 (0)\n3/2\n3 𝑔𝑔𝜇𝜇𝐵𝐵 𝑘𝑘 sp𝐵𝐵in\n𝐵𝐵 = 𝜁𝜁( )   ,\nwhere is the Boltzmann const2ant𝑀𝑀, 𝑠𝑠(0 )is 4th𝜋𝜋e𝐷𝐷 Boh(r0 m)agneton, is the Landé factor,\nand 𝑘𝑘𝐵𝐵 is the Riemann ze𝜇𝜇ta 𝐵𝐵 function. By fitting th𝑔𝑔e experimental M-T\n3\ncurve𝜁𝜁 ((F2)ig≈. S22.56)1, 2we extracted the coefficient , which yields a\n−5 −3/2\nzero-temperature spin stiffness constant 𝐵𝐵 = 4.61×10 𝐾𝐾 .\nspin\n−22 2\nSubsequently, the exchange stiffness c𝐷𝐷onst(a0n)t =at 20. 2K2,6 d×en1o0ted aJ/s nAm(0), is derived\nusing the relation13,15:\nspin\n𝐷𝐷 (0)𝑀𝑀𝑠𝑠(0) −12\nTo estimate the ex𝐴𝐴ch(a0n)g=e stiffness at finite= te2m.1p8er9at×ur1e0s (e.gJ./, m30.0 K), we applied the\n2𝑔𝑔𝜇𝜇𝐵𝐵\nscaling law with the exponent γ set to 1, consistent with mean-field theory\napproximation16:\n.\n1+𝛾𝛾\n𝑀𝑀𝑠𝑠(𝑇𝑇)\nHere 𝐴𝐴 (,𝑇𝑇 ) ≅ 𝐴𝐴(0)𝑀𝑀𝑠𝑠(0) and the density of\nFGaT17 i𝑀𝑀s 𝑠𝑠(0) = 52.27 emu /. g The 𝑀𝑀c𝑠𝑠a(l3cu0l0a)te=d 37 . 5v3a leume ua/tg 300 K is\n3\n𝜌𝜌 = 6 .981 g/cm 𝐴𝐴 𝐴𝐴(300) =\n−12\n21.. 1E3st×im1a0tionJ /omf Effective Anisotropy Constant (\neff\n)\nThe effective magnetic anisotropy energy density𝐾𝐾,\neff\n, was evaluated based on the\nin-plane saturation field (\nSIP\n) and saturation magne𝐾𝐾tization (\nS\n) obtained from the\nM-H measurements (Fig. S𝐵𝐵26-). Following the method described 𝑀𝑀in previous studies18,19,\neff\nis calculated as:\n𝐾𝐾 J/m\neff S-IP\n1 5 3\n3. Estimation of DMI C𝐾𝐾onst=ant 𝜇𝜇( 0𝑀𝑀) 𝑆𝑆 𝐵𝐵 = 5.2×10\ncorrelates the DMI constant with the geometric size of isolated skyrmions. For an\nultrathin ferromagnetic film, the skyrmion radius R is expressed as a function of\nintrinsic magnetic parameters20:\neff 𝐴𝐴 eff\n𝑅𝑅 = 𝜋𝜋𝐷𝐷 2 2 2 .\nThen 16𝐴𝐴𝐾𝐾 −𝜋𝜋 𝐷𝐷 𝐾𝐾\neff\neff\n4𝐾𝐾 𝑅𝑅 𝐴𝐴\n𝐷𝐷 =  2.\nUsing the average skyrmion radius𝜋𝜋 𝐴𝐴+𝐾𝐾 o𝑅𝑅bserved in our experiment (Fig.\nS27) and the aforementioned values 𝑅𝑅for= 97 nm and eff\n−12\nJ/m , we can estimate the DMI magnit𝐴𝐴ud=e. 1T.1h3e ×res1u0ltingJ /DmMI cons𝐾𝐾tant= is 5.2×\n5 3\n10 mJ/m . 𝐷𝐷 =\n0.98\n,\neff\nand skyrmion radius , and the theoretica𝐷𝐷l model assumes an isolated\n𝐴𝐴skyr𝐾𝐾mion profile, so it is only 𝑅𝑅an estimation of DMI constant by these magnetic\nparameters from the experiment. Nevertheless, the estimated value falls within a\nreasonable range for vdw ferromagnets and supports the stabilization of skyrmions\nobserved in our experiments.\nWe have also incorporated a specific discussion of this experimental DMI estimation\ninto the Discussion section of the revised Main Text (Page 15, Lines 15-20):\nAdditionally, quantitative analysis confirms that the symmetry breaking at the\nFeTe /FGaT interface induces a substantial DMI. By correlating the measured skyrmion\n2\nsize with the material’s exchange stiffness and anisotropy, we extracted a DMI constant\nof D ≈ 0.98 mJ/m2 (see Supplementary Note 2). This value provides direct evidence\nthat the field-cooling-induced interface generates a DMI strong enough to modify the\nmagnetic ground state from trivial stripe domains to topological skyrmion textures.\nSummary of revisions following Comment-1: We have provided a direct quantitative\nexperimental estimation of the DMI constant in Supplementary Note 2, supplemented\nby new Supplementary Figures (S25-S27) detailing the measurement of exchange\nstiffness (A) and anisotropy (K ). Concurrently, we have incorporated a discussion of\neff\nthis experimental DMI quantification into the Discussion section (Page 15, Lines 15-\n20) of the revised Main Text to fully substantiate the physical model.\nComment-2: The authors have done first-principles calculations for the FGT to verify\ntheir experimental results. In page 9, the authors claim that “These computations\nconfirm that FeTe2/FGaT interface induced DMI enhancement fundamentally\nreconfigures spin textures.” However, they did not give any DMI data from first-\nprinciples. I suggest the authors to do first-principles calculations for the DMI strength,\nfollowing the method Phys. Rev. Lett.115, 267210 (2015); Nat. Rev. Phys. 5, 43 (2023).\nResponse to Comment-2: We genuinely appreciate the reviewer’s critical assessment\nand the constructive suggestion regarding the verification of DMI strength. We\napologize for the confusion caused by the imprecise terminology used in our original\nmanuscript. When we stated that ‘these computations confirm’ the reconfiguration of\nspin textures, we were strictly referring to the micromagnetic simulations we performed\nbased on the experimental parameters, rather than first-principles density functional\ntheory (DFT) calculations. We acknowledge that the term ‘computation’ was\nmisleading in this specific context, and we have corrected all such instances to\n‘simulation’ in the revised manuscript (Page 9, Line 8) to accurately reflect our\nmethodology.\nRegarding the reviewer’s suggestion to perform first-principles calculations for the\nDMI strength, we have carefully studied the recommended references, specifically\nYang et al. [Phys. Rev. Lett. 115, 267210 (2015)] and the technical review [Nat. Rev.\nPhys. 5, 43 (2023)]. We fully agree that the DFT calculation based on the constrained\nmoment method or spin-spiral calculations, as detailed in these seminal works,\nrepresents the gold standard for theoretically and quantitatively determining interfacial\nDMI. However, in the context of the present work, our primary focus lies in the\nexperimental realization and manipulation of spin textures. To strictly validate our\nconclusions, we have now experimentally quantified the DMI strength as D ≈ 0.98\nmJ/m2 in our system (See details in Response to Comment-1). We believe that this\nquantitative experimental value serves as a solid basis for our micromagnetic\nsimulations and the subsequent analysis of spin texture reconfiguration.\nAdditionally, although we did not perform DFT calculations, we fully recognize the\nsignificance of the theoretical framework provided in the recommended references.\nWe have cited these two seminal works (labeled as ref. 52, 53) and incorporated the Fert-\nLevy model to mechanistically support our conclusions regarding the origin of the\ninterfacial DMI.\nSummary of revisions following Comment-2: We have corrected ‘computations’ to\n‘simulations’ to ensure terminological accuracy (Page 9, Line 8). Furthermore, we cited\nthe suggested references (labeled as ref. 52, 53) to support the origin of the interfacial\nDMI (Page 15, Lines 12).\nComment-3: It is suggested to add labels for temperature and magnetic field strength\nto Fig. 1b and Fig. 1c.\nResponse to Comment-3: We thank the reviewer for the suggestion to improve the\nclarity of the figures. We have now explicitly added the labels indicating the magnetic\nfield conditions (Pristine and 200 Oe FC) and the measurement temperature (T=300 K)\ndirectly onto Fig. 1b and 1c in the revised manuscript.\nSummary of revisions following Comment-3: Labels specifying the measurement\ntemperature (T = 300 K) and the magnetic states (Pristine vs. 200 Oe FC) have been\nadded to Fig. 1b and 1c to ensure the experimental conditions are immediately apparent\nto readers.\nComment-4: The article mentions that the characteristic Raman peaks of FeTe2 still\nexist under zero field condition, yet relevant data are lacking.\nResponse to Comment-4: We appreciate the reviewer’s rigorous attention to\nexperimental conditions. We would like to clarify that the formation of the FeTe phase\n2\nis an irreversible precipitation process induced during the FC treatment. Once the FeTe\n2\ncrystals are formed, they are structurally stable and do not disappear upon the removal\nof the external magnetic field. In fact, all Raman spectra presented in the original\nmanuscript were ex-situ acquired under zero magnetic field after the FC process was\ncompleted and the external magnet was removed. To explicitly clarify this, we have\nupdated the caption of Fig. 1d to state that the spectrum was collected at zero field (Page\n25).\nSummary of revisions following Comment-4: We have updated the caption of Fig.\n1d to explicitly include the ‘at zero field’ condition (Page 25).\nReviewer #3 (Remarks to the Author):\nThe manuscript by Xia .et.al. deals with the determination of different phases during\nthe annealing process of Fe3GaTe2 and Fe3GeTe2 crystals and its impact on the\nformation of magnetic textures. The authors provide an extensive characterization to\nsupport their claims. While the data clearly points to the formation of a secondary phase\n(FeTe2) that precipitates in a crystalline way towards the surface, the mechanism of\nskyrmion formation and claimed “enhancement of DMI interaction” is not well\ndescribed and understood.\nResponse: We are sincerely grateful to the reviewers for raising critical questions\nregarding the nature of the DMI evidence, which prompted us to undertake crucial\nclarifications and reinforcements of our core conclusions. We recognized that our\ndiscussion of DMI and skyrmion formation is somewhat inadequate, which is also\nmentioned by reviewer #1. We have substantially revised the paper in three key areas\nto directly address and resolve this concern.\nFirstly, we acknowledge that the term ‘enhancement’ may imply a misunderstanding\nof the intrinsic DMI. The core finding of our work is that in the originally center-\nsymmetric FGaT, the DMI is engineered ‘from nothing to something’ at the FeTe /FGaT\n2\ninterface through field cooling. We have therefore amended the title from ‘enhancement’\nto ‘emergence’ and made similar revisions elsewhere in the article to more accurately\ndescribe this physical process.\nSecondly, we have added a detailed theoretical discussion in Supplementary Note 1,\nclearly elucidating how interface symmetry breaking induces the DMI and how the\nstrength of the DMI determines the physical chain of events stabilizing the skyrmions.\nThis aims to provide a more robust theoretical foundation for the observed phenomena.\nIt reads:\nSupporting Note 1 | Discussion of symmtry breaking, DMI emergence and\nskyrmion formation\nThe Dzyaloshinskii-Moriya interaction (DMI) is an antisymmetric exchange\ncoupling that favours a chiral, non-collinear alignment between neighbouring spins1-4.\nIt is described by the Hamiltonian , where the\nDM\nvector reflects the interplay of spin-orbit coℋuplin=g a𝐃𝐃n𝑖𝑖d𝑖𝑖 ⋅lo(c𝐒𝐒a𝑖𝑖l× st𝐒𝐒ru𝑖𝑖)ctural asymmetry.\nIn a cry𝐃𝐃st𝑖𝑖a𝑖𝑖l with inversion symmetry, for every bond there exists an equivalent\nbond with , leading to complete cancellatio(n\n𝑖𝑖\n, a 𝑗𝑗)nd a vanishing net DMI. In\nour case, the𝐃𝐃 p𝑖𝑖𝑖𝑖ri=sti−ne𝐃𝐃 F𝑖𝑖𝑖𝑖GaT crystallizes in the centrosymmetric space group (P6\n3\n/mmc).\nConsequently, it exhibits no macroscopic DMI. Following FC, the formation of the\nFeTe /FGaT interface in the sample results in the disruption of the global structural\n2\ninversion symmetry, enabling the emergence of a finite, interfacial DMI.\nThe magnetic order and domain configuration in a ferromagnet are determined by\nthe competition between several fundamental energies. Within the continuum theory,\nwhich is appropriate for describing mesoscopic textures like domain walls and\nskyrmions3,5,6, the free energy density is given by:\nex ani dip dmi\nℱ = ℱ +ℱ +ℱ +ℱ\nHere, is the exchange energy density, where\nex\n2 2 2\nis th e eℱxch=an𝐴𝐴g[e( ∇st𝑚𝑚iff 𝑥𝑥 n)es+s. (T∇h𝑚𝑚is 𝑦𝑦 t)erm+ (p∇e𝑚𝑚na 𝑧𝑧 li)ze]s spatial variations in magnetization,\n𝐴𝐴favouring a uniform spin alignment.\nani\nis the uniaxial anisotropy energy\n2\nwhich aligns the magnetization alongℱ the =eas−y𝐾𝐾 (𝑢𝑢o𝑚𝑚ut𝑧𝑧-of-piane) axis, wiht being the\nuniaxial anisotropy constant. is the magnetosta𝐾𝐾ti 𝑢𝑢 c (dipole)\ndip\n1\nenergy density where is the mℱagne=tiz−ati2o𝜇𝜇n 0 v𝐌𝐌ec⋅to𝐇𝐇r 𝑑𝑑 and is the demagnetizing field\ngenerated by itself.𝐌𝐌 This energy drives the formation o𝐇𝐇f m𝑑𝑑agnetic domains to reduce\nstray fields. C𝐌𝐌ritically,\ndmi\nis the Dzyaloshinskii–Moriya interaction (DMI) energy\ndensity. For an interfaceℱ with broken inversion symmetry along the surface normal ( -\naxis), it takes the form7: 𝑧𝑧\ndmi\n∂𝑚𝑚𝑥𝑥 ∂𝑚𝑚𝑧𝑧 ∂𝑚𝑚𝑦𝑦 ∂𝑚𝑚𝑧𝑧\nℱ = 𝐷𝐷𝑚𝑚𝑧𝑧 −𝑚𝑚𝑥𝑥 +𝑚𝑚𝑧𝑧 −𝑚𝑚𝑦𝑦 \nwhere is the DMI consta∂n𝑥𝑥t. This te∂rm𝑥𝑥 is finit∂e 𝑦𝑦only in n∂o𝑦𝑦n-centrosymmetric\nstructures 𝐷𝐷and energetically favors a fixed, chiral rotation between neighbouring spins,\nwhich is the fundamental mechanism that stabilizes Néel-type domain walls and,\nultimately, magnetic skyrmions3,8.\nIn our case, the pristine FGaT with a centrosymmetric structure results in a negligible\nDMI ( ). Consequently, the magnetic state is governed by the competition\ndmi\namong ℱthe re≈m0aining three energy terms. The strong perpendicular magnetic anisotropy\n(PMA) aligns spins uniformly out-of-plane. The magnetostatic energy counteracts this\nby favoring the subdivision of the magnetization into domains of alternating polarity to\nminimize the stray field energy, while the exchange energy penalizes overly sharp\ndomain walls, promoting smooth variations. Crucially, none of these three interactions\nfavours a specific chiral rotation of spins. The balance achieved among them stabilizes\na non-chiral, maze-like (stripe) domain pattern as the magnetic ground state, consistent\nwith our experimental observations (Fig. 1b).\nFollowing FC, the FeTe /FGaT interface intrinsically breaks the global inversion\n2\nsymmetry of the system, giving rise to a finite DMI energy density . Consequently,\ndmi\nthe magnetic energy landscape is fundamentally augmented byℱ this fourth, non-\ncollinear term. While the perpendicular anisotropy continues to align spins out-of-plane\nand the magnetostatic energy still favors domain subdivision, the DMI acts as a chiral\nselector. It energetically favours Néel-type domain walls with a fixed rotational\nhandedness, introducing a macroscopic preference for non-collinear spin arrangements\nthat was absent in the pristine state. When the DMI strength exceeds a critical threshold,\nthe energy gain from forming an array of topological magnetic skyrmions can outweigh\nthe energy cost of their compact morphology compared to the non-chiral maze-like\ndomain phase9,10. The applied magnetic field during the FC process further assists in\nnucleating this ordered state. Therefore, the new ground state under these conditions\nbecomes stable skyrmions (Fig. 1c), directly manifesting the presence and action of the\nemergent interfacial DMI.\nThus, the observation of a transition from a maze-like domains to stable skyrmions\nformation after FC provides direct and intuitive experimental evidence that a significant\nDMI has emerged at the engineered interface. The skyrmions themselves are the\nmacroscopic manifestation of the underlying DMI, marking a transition in the magnetic\nground state driven by symmetry-breaking interfacial engineering.\nWe believe this explanation can effectively clarifies the relationship among\nsymmetry breaking, DMI, skyrmion formation. Specifically, it theoretically accounts\nfor emergence of non-zero DMI induced by the FeTe /FGaT interface and highlights\n2\nthat the observed transition from maze-like domains to skyrmions is also direct\nqualitative experimental evidence of DMI generation.\nMore importantly, we provide a direct experimental estimation of the DMI constant,\nconstituting the most central new evidence in this revision. We performed independent\ncalculations of DMI constant by using a semi-analytical model (Supplementary Note\n2), incorporating the average skyrmion diameter measured from MFM images (Fig.\nS27) alongside the exchange stiffness (A) and anisotropy constant (K ) of FGaT.\neff\nThe resulting DMI constant D ≈ 0.98 mJ/m2 indicates a strong interfacial interaction.\nThis experimentally derived value provides direct, quantitative support for our conclusion\nthat the FeTe /FGaT interface generates significant DMI sufficient to induce skyrmion\n2\nformation. The detailed calculation procedure is described in Supplementary Note 2:\nSupporting Note 2 | Experimental estimation of magnetic parameters and DMI\nconstant\n1. Determination of Exchange Stiffness ( )\nTo quantify the exchange interaction, 𝑨𝑨we analyzed the thermal demagnetization\nbehavior of the sample. In the low-temperature regime, the reduction of saturation\nmagnetization M (T) due to spin-wave excitations can be described by the Bloch\nS\n3/2\nlaw13,14:\n𝑇𝑇\n.\n𝑀𝑀𝑠𝑠(𝑇𝑇)\n3/2\nHere, M (0) represents the satur𝑀𝑀a𝑠𝑠t(io0)n= m1ag−ne𝐵𝐵ti𝑇𝑇zation at 0 K. The coefficient is\nS\nintrinsically linked to the spin-wave stiffness via the following relation𝐵𝐵13:\nspin\n𝐷𝐷 (0)\n3/2\n3 𝑔𝑔𝜇𝜇𝐵𝐵 𝑘𝑘 sp𝐵𝐵in\n𝐵𝐵 = 𝜁𝜁( )   ,\n2 𝑀𝑀𝑠𝑠(0) 4𝜋𝜋𝐷𝐷 (0)\nwhere is the Boltzmann constant, is the Bohr magneton, is the Landé factor,\nand 𝑘𝑘𝐵𝐵 is the Riemann ze𝜇𝜇ta 𝐵𝐵 function. By fitting th𝑔𝑔e experimental M-T\n3\ncurve𝜁𝜁 ((F2)ig≈. S22.56)1, 2we extracted the coefficient , which yields a\n−5 −3/2\nzero-temperature spin stiffness constant 𝐵𝐵 = 4.61×10 𝐾𝐾 .\nspin\n−22 2\nSubsequently, the exchange stiffness c𝐷𝐷onst(a0n)t =at 20. 2K2,6 d×en1o0ted aJ/s nAm(0), is derived\nusing the relation13,15:\nspin\n𝐷𝐷 (0)𝑀𝑀𝑠𝑠(0) −12\nTo estimate the ex𝐴𝐴ch(a0n)g=e stiffness at finite= te2m.1p8er9at×ur1e0s (e.gJ./, m30.0 K), we applied the\n2𝑔𝑔𝜇𝜇𝐵𝐵\nscaling law with the exponent γ set to 1, consistent with mean-field theory\napproximation16:\n.\n1+𝛾𝛾\n𝑀𝑀𝑠𝑠(𝑇𝑇)\nHere 𝐴𝐴 (,𝑇𝑇 ) ≅ 𝐴𝐴(0)𝑀𝑀𝑠𝑠(0) and the density of\nFGaT17 i𝑀𝑀s 𝑠𝑠(0) = 52.27 emu /. g The 𝑀𝑀c𝑠𝑠a(l3cu0l0a)te=d 37 . 5v3a leume ua/tg 300 K is\n3\n𝜌𝜌 = 6 .981 g/cm 𝐴𝐴 𝐴𝐴(300) =\n−12\n21.. 1E3st×im1a0tionJ /omf Effective Anisotropy Constant (\neff\n)\nThe effective magnetic anisotropy energy density𝐾𝐾,\neff\n, was evaluated based on the\nin-plane saturation field (\nSIP\n) and saturation magne𝐾𝐾tization (\nS\n) obtained from the\nM-H measurements (Fig. S𝐵𝐵26-). Following the method described 𝑀𝑀in previous studies18,19,\neff\nis calculated as:\n𝐾𝐾 J/m\neff S-IP\n1 5 3\n3. Estimation of DMI C𝐾𝐾onst=ant 𝜇𝜇( 0𝑀𝑀) 𝑆𝑆 𝐵𝐵 = 5.2×10\ncorrelates the DMI constant with the geometric size of isolated skyrmions. For an\nultrathin ferromagnetic film, the skyrmion radius R is expressed as a function of\nintrinsic magnetic parameters20:\neff 𝐴𝐴 eff\n𝑅𝑅 = 𝜋𝜋𝐷𝐷 2 2 2 .\nThen 16𝐴𝐴𝐾𝐾 −𝜋𝜋 𝐷𝐷 𝐾𝐾\neff\neff\n4𝐾𝐾 𝑅𝑅 𝐴𝐴\n𝐷𝐷 =  2.\nUsing the average skyrmion radius𝜋𝜋 𝐴𝐴+𝐾𝐾 o𝑅𝑅bserved in our experiment (Fig.\nS27) and the aforementioned values 𝑅𝑅for= 97 nm and eff\n−12\nJ/m , we can estimate the DMI magnit𝐴𝐴ud=e. 1T.1h3e ×res1u0ltingJ /DmMI cons𝐾𝐾tant= is 5.2×\n5 3\n10 mJ/m . 𝐷𝐷 =\n0.98\n,\neff\nand skyrmion radius , and the theoretica𝐷𝐷l model assumes an isolated\n𝐴𝐴skyr𝐾𝐾mion profile, so it is only 𝑅𝑅an estimation of DMI constant by these magnetic\nparameters from the experiment. Nevertheless, the estimated value falls within a\nreasonable range for vdw ferromagnets and supports the stabilization of skyrmions\nobserved in our experiments.\nGiven the significance of this quantitative validation, we have incorporated a specific\ndiscussion of this experimental DMI estimation into the Discussion section of the\nrevised Main Text (Page 15, Lines 15-20):\nAdditionally, quantitative analysis confirms that the symmetry breaking at the\nFeTe /FGaT interface induces a substantial DMI. By correlating the measured skyrmion\n2\nsize with the material’s exchange stiffness and anisotropy, we extracted a DMI constant\nof D ≈ 0.98 mJ/m2 (see Supplementary Note 2). This value provides direct evidence\nthat the field-cooling-induced interface generates a DMI strong enough to modify the\nmagnetic ground state from trivial stripe domains to topological skyrmion textures.\nIn summary, through these revisions—ranging from terminological precision and\ntheoretical clarification to the quantitative estimation of DMI—we believe we have\neffectively resolved the issues raised. We thank the reviewer for these constructive\ncomments, which have significantly improved the rigor and quality of our manuscript.\nSummary of revisions following the Reviewer’s General Comment on DMI\nMechanism: We have revised the Title and terminology from ‘enhancement’ to\n‘emergence’ throughout the manuscript to accurately reflect the symmetry-breaking\norigin. Furthermore, we have provided a comprehensive theoretical framework in\nSupplementary Note 1 and a direct quantitative experimental estimation of the DMI\nconstant in Supplementary Note 2, supplemented by new Supplementary Figures\n(S25-S27) detailing the measurement of exchange stiffness (A) and anisotropy (K ).\neff\nConcurrently, we have incorporated a discussion of this experimental DMI\nquantification into the Discussion section (Page 15, Lines 15-20) of the revised Main\nText to fully substantiate the physical model.\nIn particular, the occurrence of symmetry breaking and induced skyrmion-like magnetic\ntextures can have various origins besides the claimed FGaT/FeTe2 interface , such as\nself-intercalation, point defects, other magnetic phases, etc. Especially in systems that\nundergo precipitation, a plethora of changes may occur to the initial crystal phase. It is\nnow well known in the community that TEM data (in which the authors base) is\nextremely local for a crystal that is macroscopic and not necessarily representative of\nthe sample behaviour. Additional large-scale techniques to rule out the presence of point\ndefects (e.g. Te-deficiency) and self-intercalation of surplus Fe -which can migrate not\nonly to the top, but also to the bottom FGaT layer,- should be employed: for instance\nX-ray diffraction to resolve the FGaT structure before and after annealing (akin Phys.\nRev. Materials 4, 074008 (2020) and Physical Review Letters 133 (25), 256702 (2024)).\nResponse: We are grateful to the reviewer for highlighting these critical considerations\nregarding the potential origins of symmetry breaking and the representativeness of local\nprobes. We fully agree that phenomena such as point defects, self-intercalation, or other\nphase changes could, in principle, contribute to the DMI and observed magnetic\ntextures, and that conclusions drawn solely from local TEM characterization require\nsupport from larger-scale analyses.\nTo address these points, we have undertaken comprehensive characterization\ndesigned to assess the sample behavior on macroscopic scales. While we acknowledge\nthe highly local nature of conventional TEM, our study deliberately incorporated large-\narea, multi-region STEM/EDS analyses across both pristine and annealed samples (Fig.\nS6-S12). These extensive scans consistently revealed the precipitation of FeTe , while\n2\nshowing no evidence of widespread Te deficiency or Fe intercalation within the probed\nregions. This indicates that FeTe precipitation is a dominant and reproducible structural\n2\nchange. Crucially, to further substantiate the widespread nature of this phase\ntransformation, we have added a large-field-of-view image in Supplementary Figure\nS23, which clearly reveals the formation of FeTe across the entire observation window.\n2\nfield-of-view STEM image of the annealed FGaT sample. The image reveals the\nuniform formation of the FeTe surface layer across the entire observation window,\n2\nconfirming that the phase transformation is a macroscopic and widespread phenomenon\nrather than a localized defect.\nWe also appreciate the reviewer’s suggestion regarding XRD. In response, we have\nincluded a comparative XRD analysis of pristine and annealed FGaT in the new\nSupplementary Figure S24. The diffraction peaks remain sharp with no observable\nsplitting or significant shifting after heating. Through quantitative fitting, we\ndetermined the interplanar spacing (d) to be 0.848 Å for the pristine sample and 0.855\nÅ after annealing, representing a negligible difference of only 0.007 Å. This stability\nstands in stark contrast to these reported cases of Co doping or Fe self-intercalation,\nwhich typically induce much larger lattice variations (ranging from ~0.04 Å to ~0.25\nÅ). Moreover, Fe self-intercalation is known to cause lattice compression (reduction in\nd), whereas our data shows a minute expansion. Consequently, we conclude that the\nannealing process does not induce large-scale bulk defects or Fe self-intercalation, and\nthe marginal lattice change is likely attributable to minor lattice relaxation after\nannealing. Regarding the FeTe signal, we note that it remains indistinguishable in our\n2\nmeasurements due to the exceptionally thin (~10 nm), polycrystalline nature of the\nsurface layer and the obscuring effect of the topmost amorphous Fe-Ga complex.\nFurthermore, to explicitly address the concern regarding bulk defects, we have\nincorporated a discussion of these XRD results into the revised Main Text (Page 9,\nLines 10-20) and referenced these important literatures (labeled ref. 43, 44 in revised\nmanuscript):\nFigure S24 | X-ray diffraction (XRD) analysis of bulk structural integrity.\nComparative XRD patterns of pristine (black) and annealed (red) FGaT single crystals.\nThe (0 0 l) diffraction peaks remain sharp and well-defined after annealing, with no\nemergence of split peaks or impurity phases. The calculated interplanar spacing (d)\nshows a negligible change from 0.848 Å (pristine) to 0.855 Å (annealed). The absence\nof significant peak shifting or broadening rules out massive Fe self-intercalation or bulk\ndecomposition.\nMoreover, to directly demonstrate the macroscopic prevalence of FeTe from a\n2\nmesoscopic perspective, we performed Raman mapping as complementary large-scale\nevidence. Fig. R2 presents the Raman mapping over a 70 × 65 μm2 area on an annealed\nFGaT flake. This map shows that the characteristic FeTe Raman signature appears\n2\nubiquitously across the scanned region, unambiguously confirming that its precipitation\nis not a random or localized event, but a deterministic and sample-wide outcome of the\nannealing process.\nFig. R2 Large‑scale FeTe precipitation revealed by Raman mapping. (a) Optical\n2\nimage of an annealed FGaT flake. (b) Two‑dimensional contour map of the FeTe A\n2 g\npeak intensity (121 cm-1) obtained from Raman mapping over the region in (a),\nindicating that FeTe precipitation occurs universally across the sample, confirming it\n2\nas a macroscopic‑scale phenomenon. The scale bar is 20\nTaken together, the combination of large-scale STEM μ imm.aging, bulk XRD stability\nanalysis, and wide-area Raman mapping provides a consistent and robust confirmation:\nthe annealing process triggers a widespread surface phase transformation into FeTe\n2\nwithout compromising the bulk structural integrity of FGaT.\nSummary of revisions following the Reviewer’s General Comment on macroscopic\nuniversality of FeTe precipitation: We have added a discussion on Page 9, Lines 10-\n2\n20 of the revised Main Text to rule out bulk Fe self-intercalation based on the negligible\nlattice change observed in XRD. We have cited the important in the revised manuscript\n(Refs. 43 and 44). Correspondingly, Supplementary Figure S22 (large-scale STEM) and\nSupplementary Figure S23 (comparative XRD) have been included in the Supporting\nInformation to demonstrate macroscopic structural integrity.\nAdditionally, This is necessary to unveil the origin of the observed SHG response and\nskyrmion-like bubble formation which is one of the most important aspects of the paper.\nResponse: We fully agree with the reviewer that clarifying the origins of both the SHG\nresponse and skyrmion formation is pivotal to this work. For a detailed discussion\nregarding the SHG response, please refer to our specific response to Question 2 below.\nRegarding the mechanism of skyrmion formation, we have provided a comprehensive\ntheoretical analysis in Supplementary Note 1, as mentioned in our previous responses.\nThe authors should address this main issue in a revised manuscript, as well as several\nother points:\nComment-1: The Raman-signal in Figure 1 show a full transition from one phase to\nanother, without overlap of the two phases (as it was detected by TEM, Figure 2). The\nauthors should comment if the surface sensitivity of their Raman setup is in line with\nthe observation of only the FeTe2 phase after annealing.\nResponse to Comment-1: We sincerely thank the reviewer for this thoughtful\nobservation regarding our Raman data. The point raised is well taken, and it allows us\nto clarify an important nuance in our spectral presentation.\nWe wish to clarify that the Raman spectrum collected after annealing implies a\ncoexistence of signals rather than a complete replacement. The apparent dominance of\nthe FeTe peaks in Fig. 1d stems primarily from the much larger Raman scattering\n2\ncross-section of the precipitated FeTe phase compared to the pristine FGaT. Since the\n2\nspectra are normalized to the most intense peak for visualization, the relatively weak\nFGaT signature becomes visually suppressed on the given scale.\nRegarding the reviewer’s query on surface sensitivity: Our Raman measurements\nwere performed using a 532 nm laser, which typically has a penetration depth on the\norder of hundreds of nanometers in such materials—far exceeding the thickness of the\nsurface FeTe layer (~10 nm). Therefore, our setup probes well into the underlying\nIndeed, the underlying FGaT signal has not vanished. As we demonstrate through\ndetailed spectral fitting in the Fig. S20a, the broad feature near 150 cm-1 can be\nsuccessfully resolved, confirming the continued presence of FGaT lattice vibrations\nalongside the sharp FeTe peaks. This fitting analysis provides direct evidence that the\n2\nsample retains a composite structure (FeTe shell/FGaT core), consistent with the cross-\n2\nsectional STEM images shown in Fig. 2.\nFig.S20a\nComment-2: SHG measurements. If the creation of a non-centrosymmetric structure\nhappens only at the interface, it might reflect on a very weak signal. However, if it\ncomes from a rather bulk phenomenon, it should scale with thickness. The authors\nshould perform thickness dependent SHG measurements (samples shown in Figure 4c)\nto corroborate the origin of the signal.\nResponse to Comment-2: We thank the reviewer for raising this important point,\nwhich provides a valuable opportunity to rigorously corroborate the origin of the\nsymmetry breaking.\nFirst, we note that the absolute SHG signal from the interface is very weak. For\nreference, Fig. R3a compares the SHG spectrum of the FeTe /FGaT interface with that\n2\nof monolayer WS , a known strong SHG emitter. The interface signal is orders of\n2\nmagnitude weaker and is comparable only to the two‑photon photoluminescence (2PPL)\nbackground of monolayer WS . This low intensity further aligns with an interfacial\n2\norigin.\nNext, we performed SHG measurements on a new batch of FGaT flakes (prepared to\nensure surface freshness) with thicknesses spanning from ~27 nm to ~305 nm. As\nshown in Fig. R3b, the measured SHG intensity exhibits no correlation with sample\nthickness. This absence of scaling strongly indicates that the signal does not originate\nfrom a bulk property of the material but is instead generated at a fixed source that are\nconsistent with the FeTe /FGaT interface. Furthermore, we observed noticeable\n2\nvariation in SHG intensity even among samples of similar thickness. This is likely\nattributable to the polycrystalline nature of the precipitated FeTe , where differences in\n2\nthe local crystallographic orientation of the FeTe domains relative to the FGaT\n2\nsubstrate modulate the effective nonlinear susceptibility of the formed heterostructure.\nCollectively, the thickness-independent behavior and the inherently low signal level\nprovide compelling evidence that the detected SHG originates from the symmetry-\nbroken FeTe /FGaT interface.\nWS (reference) and the FeTe /FGaT interface. The interface signal is very weak,\n2 2\ncomparable to the two-photon photoluminescence (2PPL) background of WS . (b) SHG\n2\nintensity measured on FGaT flakes of different thicknesses after field cooling. The lack\nof systematic dependence on thickness demonstrates that the SHG arises from the\nFeTe /FGaT interface, not from a bulk effect.\nphase. What is the thickness and influence of this layer on the various measurements?\nSince it contains Fe, it is probably magnetic. Could you provide magnetization\nmeasurements of the crystals before and after annealing? Is this also possible affecting\nmagnetic bubble formation? MFM is surface sensitive so it will actually get stronger\nsignals from the topmost layer.\nResponse to Comment-3: We sincerely thank the reviewer for raising this important\npoint, which has prompted us to thoroughly examine the potential influence of the\namorphous Fe-Ga surface layer identified in our study.\nOur cross-sectional STEM analysis indicates that this Fe-Ga-rich amorphous layer is\napproximately 7 nm thick (Fig. R4). Given its nanoscale thickness and disordered\nnature, its impact on probing the underlying crystalline interface is minimal across our\ncharacterization techniques. In Raman spectroscopy, the laser penetration depth is\nseveral hundred nanometers, and the amorphous layer, lacking long-range order,\ncontributes no distinct phonon signals. The observed spectra are thus dominated by the\nunderlying FGaT and crystalline FeTe phases. Similarly, the signal of electrical dipole\nlayer cannot generate a significant SHG signal, confirming that the signal we detect\noriginates from the well-defined FeTe /FGaT interface.\nEDS mapping. The Fe-Ga rich amorphous layer is approximately 7 nm thick.\nRegarding the MFM testing, the reviewer’s concerns are entirely valid. MFM is\nindeed sensitive to surface magnetic signals. However, the critical factor determining\nMFM contrast is the local out-of-plane magnetic gradient. Although the amorphous Fe-\nGa layer contains Fe, its magnetic structure is highly disordered and lacks distinct\nperpendicular anisotropy (PMA) required to support stable domain walls or skyrmions.\nIn contrast, the sharp magnetization reversal induced by the strong PMA of FGaT\nconstitutes the primary source of the clear contrast (mazed-domains or skyrmions)\nobserved in MFM (Fig. 1b and c). The amorphous overlayer may slightly attenuate but\ndoes not fundamentally alter or generate this signal.\nMoreover, to directly assess the magnetic contribution of this layer, we performed\nmagnetization measurements of the crystals before and after annealing (Fig. R5). The\ntemperature‑dependent magnetization (M-T) and derivative (dM/dT) results in Fig.\nS23a and b indicate that the bulk FGaT crystal exhibits no change in T before and after\nC\nannealing, both remaining at 354 K. Concurrently, the Magnetization hysteresis loop\n(M-H) patterns in Fig. R5c and d remained unchanged, with only a minor variation in\nabsolute saturation magnetization intensity of less than 10%. This confirms that the\nformation of the amorphous layer did not introduce a substantial new ferromagnetic\nphase, and its contribution to the magnetic moment is negligible relative to the bulk\nFGaT, consistent with our interpretation of the MFM data.\nFig.R5 Bulk magnetic characterization of FGaT before and after annealing. (a, b)\nTemperature‑dependent magnetization (M‑T) curves and their derivatives (dM/dT)\nmeasured under 1000 Oe out-of-plane magnetic field. The Curie temperature (T )\nC\nremains at 354 K after annealing. (c, d) Magnetization hysteresis loops (M‑H) measured\nat 300 K. The saturation magnetization shows only a minor change (<10%), indicating\nthe amorphous surface layer contributes negligibly to the total magnetic moment.\nComment-4: How do you get the DMI constant of the FeTe2/FGaT interface as D =\n2.0 mJ/m2? Can you provide calculation/estimation details?\nResponse to Comment-4: We thank the reviewer for this pertinent question regarding\nthe determination of the DMI constant. The value D=2.0 mJ/m2 was derived from\nparameterized micromagnetic simulations designed to quantitatively match our key\nexperimental observations.\nBy systematically varying DMI constant while using independently measured\nmaterial parameters, we found that only when the DMI constant reached approximately\n2.0 mJ/m2 could the simulations consistently reproduce the experimental outcomes:\nspecifically, the field-cooling-driven transition from mazed-like domains to a stable\nskyrmion lattice (Fig. S14), as well as the emergence of diverse topological spin\ntextures such as skyrmion bags under varying magnetic fields (Fig. S13). This\nmagnitude is also consistent with D value reported in other interface-engineered van\nder Waals heterostructures21, lending further support to our parameter choice.\nAdditionally, as detailed in the response to the previous question, we have performed\nan independent experimental estimation of the DMI constant that\nmJ/m (Supplementary Note 2). The close agreement between the simula𝐷𝐷tio≈n\n2\n0va.9lu8e ( mJ/m ) and the experimentally derived estimate ( mJ/m ) strongly\n2 2\nreinforces the reliability of our DMI quantification. While there is a numerical deviation\n2.0 0.98\nbetween the simulation parameter ( mJ/m ) and the analytical estimate ( mJ/m )\n2 2\ndue to the idealized assumptions in the analytical model versus the complex spin\n2.0 0.98\ntextures in simulations, both values are of the same order of magnitude ( mJ/m ).\n~1−2\nparameters, confirming that the FeTe /FGaT interface generates a significant DMI\n2\nsufficient to stabilize the observed room‑temperature skyrmions.\nComment-5: The title states: “enhancement of DMI”, but there is no direct\nexperimental evidence of DMI enhancement. The magnetic bubble formation is a hint\nthat DMI might be the reason behind, but is very qualitative and does not merit the\nclaim in the title. Even though, it is not clear whether it is a bulk or an interface-driven\nDMI. Either the authors bring more quantitative evidence or they should tone down the\nDMI statements in the manuscript.\nResponse to Comment-5: We sincerely thank the reviewer for this critical comment,\nwhich has helped us clarify and strengthen the central claim of our work. We apologize\nagain that the term ‘enhancement’ in the original title could be misinterpreted and might\nimply the amplification of a pre-existing DMI, which was not our intended message.\nAs the reviewer astutely points out, our core discovery is the origin of the DMI in a\npreviously centrosymmetric system, which is a transition from zero to a finite value\ndriven by interface engineering. Therefore, in the revised manuscript, we have changed\nthe title to use the term ‘emergence’ to more accurately reflect this ‘creation’ mechanism.\nThe title now is ‘Spontaneous Emergence of Dzyaloshinskii-Moriya Interaction via\nField-Cooling-Induced Interface Engineering in 2D Ferromagnetic ternary Tellurides’.\nConsistent with this clarification, we have also updated the terminology in the revised\nmanuscript. We replaced previous descriptions like ‘enhanced’ or ‘enhancing’ with\n‘emergent’, ‘induced’, or ‘interfacial’. Similarly, verbs such as ‘gives rise to’ and\n‘triggers the onset of’ are now used to describe the DMI origin, ensuring the text\naccurately reflects the generation of DMI from the symmetry-breaking interface, rather\nthan the amplification.\nMore importantly, to address the request for more direct and quantitative evidence,\nwe have significantly strengthened the manuscript in two key respects. First, we have\nexpanded the theoretical discussion to explicitly articulate the relationship between\ninterfacial symmetry breaking, the emergence of finite DMI, and skyrmion stabilization\n(see Supplementary Note 1). Second, and most critically, we now provide\nan experimentally derived, quantitative estimate of the DMI constant. By applying an\nestablished analytical model to the measured skyrmion diameter from our MFM images,\nwe obtain a DMI strength of D = 0.98 mJ/m2 (See Supplementary Note 2). This value\nis of the same order of magnitude as the parameter used in our micromagnetic\nsimulations to replicate the experimental observations. We believe this independent\nquantification moves our evidence beyond qualitative correlation and substantiates our\nclaim regarding the interface-driven emergence of DMI.\nSummary of revisions following Comment-5: We have revised the Title to\n‘Spontaneous Emergence of...’ on Page 1, Line 1 and updated related terminology\nthroughout the manuscript (e.g., Page 2, Line 10, Page 4, Line 1…) to accurately reflect\nthe ‘creation’ mechanism. Corresponding theoretical clarifications and quantitative\nevidence are now detailed in Supplementary Note 1 and Supplementary Note 2,\nrespectively.\nComment-6: In the laser-patterning experiment, is it possible to control laser\nparameters and define the boundaries of FeTe2 formation, similar to the heating study?\nThat would serve as a practical guide for other scientists that may want to reproduce\nthe results.\nResponse to Comment-6: We thank the reviewer for highlighting the importance of\ncontrollability and reproducibility in the laser-patterning process.\nRegarding the definition of boundaries, the spatial resolution of the FeTe formation\n2\nis fundamentally governed by the laser spot size and the thermal diffusion profile. Based\non Raman mapping data (Fig. 5b), the boundaries of FeTe formation are approximately\n2\nbetween 800 nm-1 μm. This scale is consistent with the optical diffraction limit of our\nsetup. While higher resolution (sub-diffraction limit) would require near-field optical\ntechniques, the current micrometer-scale precision is sufficient to define distinct\nmagnetic patterns for skyrmion confinement.\nMost importantly, to serve as a practical guide for reproduction, we have\nmeticulously updated the Methods section (Page 19, Lines 3-11). We now detailed our\nlaser irradiation parameters including wavelength, numerical aperture (NA), laser\npower density, and exposure time. This ensures that other researchers can accurately\nreproduce the reported laser-patterning results.\nSummary of revisions following Comment-6: We have updated the Methods section\non Page 19, Lines 3-11 with detailed laser-patterning parameters.\nComment-7: “The bond-free vdW interfaces in FeTe2/FGaT enable seamless\nintegration of dissimilar materials without lattice-matching constraints, preserving spin\ncoherence for low-1 power spintronic devices.” This sentence is misleading. The\npreservation of spin coherence is not automatically given at a vdW interface of\ndissimilar materials.\nResponse to Comment-7: We sincerely thank the reviewer for this insightful comment.\nWe fully agree that the preservation of spin coherence is not an automatic consequence\nof vdW interfaces and that our original statement was overly broad and potentially\nmisleading. We apologize for this lack of precision.\nOur intended meaning was to highlight the potential structural advantage of the vdW\ninterface in mitigating spin scattering compared to traditional, covalently bonded\nheterointerfaces. The absence of strong chemical bonds and the associated lattice-\nmatching constraints at the vdW interface are known to reduce interfacial defects,\ndisorder, and intermixing, which are major sources of spin decoherence22-24. Therefore,\nwhile not ‘automatically’, a clean vdW interface provides a more favorable platform\nfor preserving spin coherence.\nTo substantiate this point and address the reviewer’s concern, we have now modified\nthe sentence in the manuscript (Page 15, Lines 13-14) to more accurately reflect this\nnuanced perspective. The revised text now reads:\nThe bond-free vdW interfaces in FeTe /FGaT enable seamless integration of dissimilar\n2\nmaterials without lattice-matching constraints, effectively minimizing interfacial\nscattering sources and thereby offering a promising platform for preserving spin\ncoherence in low-power spintronic devices.\nSummary of revisions following Comment-7: We have refined the statement\nregarding spin coherence on Page 15, Lines 13-14 of the revised Main Text."}, {"round": 2, "reviewer_comments": {"reviewer_1": "All of my concerns have been adequately addressed, and I recommend that the manuscript should be accepted for publication.", "reviewer_2": "The authors have addressed all my concerns. I recommend its publication.", "reviewer_3": "The authors have adequately addressed most of my concerns. In particular, the explanation of the DMI emergence and the experimentally inferred estimation of the DMI constant adds value and strengthens the main claim of the manuscript. In that respect, I appreciate that the authors followed my suggestion to look and quantify the magnetization data which helped in the derivation of various magnetic parameters such as exchange stifness and anisotropy constant. The title has also been adapted to match the experimental scenario more realistically. Although the structure of the FGaT after annealing has not been resolved via XRD to rule out competing origins for the DMI, the additional characterization (e.g, large-scale Raman and TEM) helped to assess that FeTe2 is the dominant additional structural feature across the crystal, clarifying most of the doubts.\nHowever, my two last points need a minor round of revision:\n- Regarding laser patterning, what I meant was not necessarily the spatial boundaries of the phase change, but the boundary conditions in terms of power/flux to attain the FeTe2 phase. There must be a threshold power value for the onset of the phase change (it would be interesting though, whether this threshold is also thickness dependent like the thermal treatment) as well as a critical value on the high power side which leads to beam damage. To mention this kind of operating window in the methods section would be beneficial for the reader.\n- The implication on reduced spin scattering at vdW interfaces and spin coherence for eventual devices is too far fetched. The experimental scenario is much more complicated and unless experiments for this particular system are carried out, the authors should refrain from giving such statements."}, "author_response": "Response: We sincerely thank the reviewer for recommending our manuscript to be\npublished in Nature Communications. The valuable suggestions and comments\nfurnished by the referee have significantly contributed to enhancing the quality of our\nmanuscript.\nResponse: We are deeply grateful to the reviewer for confirming that their concerns\nhave been adequately addressed and for endorsing the publication of our work. We\nthank them for their time and valuable insights, which have been instrumental in\nrefining our manuscript for Nature Communications.\nResponse: We sincerely thank the reviewer for their valuable suggestions and\ncomments, and for acknowledging the value of our supplementary analysis, which have\nsignificantly contributed to enhancing the quality of our manuscript.\nResponse to Comment-1: We appreciate the reviewer’s helpful suggestion regarding\nthe definition of the operating boundary conditions. We agree that establishing a clear\npower window is essential for reproducibility. To address this, we performed detailed\npower-dependent Raman measurements to identify the phase change threshold and the\ndamage limit.\nAs shown in Fig. R1a, we selected a representative thick FGaT flake (~70 nm) and\nmonitored the Raman evolution with increasing laser power. We identified an operating\nwindow between 0.5 mW and 4 mW. The onset of FeTe precipitation—indicated by\n2\nthe emergence of characteristic Raman peaks—occurs at approximately 0.5 mW, while\nlaser-induced surface structure damage is observed when the power reaches 5 mW.\nTherefore, our chosen parameter of 2.5 mW sits safely within this window to ensure\nrobust phase transformation without degradation. We determined the sample damage\nbased on two criteria: the appearance of distinct ablation marks in the optical\nmicrographs (Fig. R1e, obtained after 5 mW irradiation) and a significant reduction in\nthe overall Raman signal intensity (Fig. R1a, red line at 5.0 and 6.0 mW).\nTo further verify the universality of this window and its relation to sample thickness,\nwe performed identical power-dependent measurements on 28 nm (Fig. R1b) and 15\nnm (Fig. R1c) flakes. The results confirm that the thickness threshold observed in\nthermal annealing (Fig.4) also applies to laser patterning due to the photothermal nature\nof the process. For samples thicker than the threshold (e.g., 28 nm and 70 nm), an\noperating window (0.5–4 mW) exists where FeTe forms stably. In contrast, for the 15\n2\nnm flake (below the ~25 nm threshold), physical damage occurs at a lower power of ~1\nmW (Fig. R1i), and notably, no FeTe signal is detected prior to this destruction\n2\n(Fig.R1c).\nBased on these findings, we have updated the Methods section (‘Laser patterning and\nlocalized phase engineering’) to provide specific guidelines for readers: one must select\nFGaT flakes with a thickness greater than 25 nm, and the laser power should be\nmaintained within the 0.5 mW to 4 mW range to successfully induce the phase transition\nwithout damaging the sample. Accordingly, we have also revised the main text to\nexplicitly mention that the experimental laser power was optimized within this\ndetermined safe operating window. The specific modifications in the manuscript are\nshown below.\nMain Text Revisions (Page 13, Lines 7-9): The laser power was set to 2.5 mW, which\nwas optimized to be within the safe operating window for FeTe precipitation (see\nMethods Revisions (Page 19, Lines 6-8): For the deterministic creation of isolated\nskyrmions via optothermal writing, a continuous‑wave laser (532 nm) was focused\nthrough a 100x objective lens (NA=0.9) onto the surface of the FGaT flake (thickness >\n25 nm). The laser power was set to 2.5 mW, selected within the determined operating\nwindow of 0.5–4 mW (bounded by the phase transition threshold and ablation limit),\nand the exposure time for each irradiation spot was fixed at 5 minutes.\nFigure R1 | Power-dependent Raman spectra and optical characterization of\nFGaT flakes with different thicknesses. (a–c) Evolution of Raman spectra with\nincreasing laser power for FGaT flakes with thicknesses of (a) 70 nm, (b) 28 nm, and\n(c) 15 nm. For flakes >25 nm (a and b), FeTe peaks emerge around 0.5 mW. For the\n2\n15 nm flake (c), no FeTe signal appears before damage. (d–i) Corresponding optical\nimages of the laser irradiation spots. (d, f, h) Optical images of the 70 nm, 28 nm, and\n15 nm flakes, respectively, showing the spots after irradiation at safe powers (within\nthe operating window for thick samples). (e, g, i) Optical images of the same spots after\nirradiation exceeding the damage threshold, clearly showing the formation of laser-\ninduced ablation marks (highlighted by dashed circles and arrows), which correspond\nto the irreversible sample damage.\nSummary of revisions following Comment-1: We have updated the ‘Laser patterning\nand localized phase engineering’ section in the Methods (Page 19, Lines 6-8) and\ncorresponding main text (Page 13, Lines 7-9) to explicitly define the operating power\nwindow (0.5 mW–4 mW) and the thickness-dependent behavior.\nResponse to Comment-2: We sincerely thank the reviewer for pointing out the issue\nof overinterpretation in our manuscript. Indeed, the claim regarding spin coherence and\nreduced scattering is speculative without specific transport measurements on the\ninterface. To ensure the scientific rigor of our manuscript, we have removed this\nstatement from the Discussion section (Page 14, Lines 12-13). The revised text now\nfocuses solely on the structural advantage of the vdW interface (seamless integration)\nwithout extending the claim to spin coherence properties. It now reads:\nThe bond-free vdW interfaces in FeTe /FGaT enable seamless integration of\n2\ndissimilar materials without lattice-matching constraints. [The subsequent sentence\nregarding spin coherence has been removed]\nSummary of revisions following Comment-2: We have removed the sentence\ndiscussing ‘spin coherence’ and ‘interfacial scattering’ from the Discussion section to\navoid over-interpretation (Page 14 Line 12)."}]

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