Lattice dynamics and phonon dispersion of van der Waals layered ferromagnet Fe3GaTe2

Deren Li; Dinghua Yang; Gang Xiang; Jiating Lu; Li Lei; Wenjie He; Xia Chen; Xi Zhang; Yong Peng; Yu Li

REVIEW 3 major objections 5 minor 3 references

Lattice dynamics and phonon dispersion of van der Waals layered ferromagnet Fe3GaTe2

T0 review · 3 major / 5 minor · reviewed 2026-08-12 · deepseek-v4-flash

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Pith's one-line read The paper reports a room-temperature spin-phonon coupling strength of about 0.81 cm-1 for the E2g^2 lattice mode of Fe3GaTe2.

desk verdict Useful Raman dataset and a plausible mode reassignment, but the room-temperature spin-phonon claim collapses on the paper's own numbers. read the letter →

arxiv 2411.16463 v2 pith:NEQ6UBOV submitted 2024-11-25 cond-mat.mtrl-sci cond-mat.mes-hall

Xia Chen , Xi Zhang , Wenjie He , Yu Li , Jiating Lu , Dinghua Yang , Deren Li , Li Lei

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Yong Peng Gang Xiang

This is my paper · ORCID

classification cond-mat.mtrl-scicond-mat.mes-hall PACS 63.20.-e78.30.-j

keywords Fe3GaTe2vanderWaalsferromagnetspin-phononcouplingRamanspectroscopyhighpressurephonondispersionlatticedynamicsanharmonicity

verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

Fe3GaTe2 is a van der Waals ferromagnet that orders above room temperature, and the paper asks whether its lattice vibrations feel the magnetic order. Combining Raman spectroscopy from 80 K to 690 K and from ambient pressure to 19.5 GPa with first-principles phonon calculations, the authors assign the two observed Raman modes, show that the lower-energy $E_{2g}^{2}$ mode is anharmonic while $A_{1g}^{1}$ is quasi-harmonic, and find that below the 360 K magnetic ordering temperature both the energy and the linewidth of $E_{2g}^{2}$ deviate from an anharmonic model. They interpret the 0.25 cm$^{-1}$ deviation at 300 K as spin-phonon coupling with strength ~0.81 cm$^{-1}$, which would be the first room-temperature spin-phonon coupling reported in a van der Waals ferromagnet. If correct, this shows magnetic order can reshape lattice dynamics at operating temperatures relevant to spintronics.

What carries the argument

The argument runs on three connected pieces. (1) Mode identification: space-group analysis of the $P6_3/mmc$ structure plus calculated phonon dispersion and displacement patterns assign the 126.0 and 143.5 cm$^{-1}$ Raman peaks to $E_{2g}^{2}$ and $A_{1g}^{1}$. (2) Anharmonic fitting: the temperature dependence of phonon energy and FWHM is fitted above $T_c$ with the two-phonon/three-phonon decay model, so any deviation below $T_c$ is defined as a non-anharmonic contribution. (3) The spin-phonon relation $\omega \approx \omega_0 + \lambda \langle S_i \cdot S_j \rangle$, together with a magnetization-derived $\langle S_i \cdot S_j \rangle$, converts the 0.25 cm$^{-1}$ deviation into a coupling strength. The pressure response (softening $E_{2g}^{2}$, stiffening $A_{1g}^{1}$, inflection at 7.6 GPa) is used to separate volume and strain effects from spin effects.

What would settle it

Measure the $E_{2g}^{2}$ peak on multiple Fe3GaTe2 flakes with a spectrometer calibrated to better than 0.1 cm$^{-1}$ and report run-to-run scatter: if the 300 K deviation from the anharmonic model is comparable to the scatter, the claimed 0.81 cm$^{-1}$ coupling is below the detection limit. A field-dependent Raman experiment through $T_c$ would settle the mechanism: if the anomaly does not move with applied magnetic field, it is not spin-phonon coupling.

Watch

Extended reading notes

Core claim

The central claim is that spin ordering is load-bearing for the $E_{2g}^{2}$ phonon but not for $A_{1g}^{1}$: first-principles calculations put the nonmagnetic $E_{2g}^{2}$ frequency at 98.3 cm$^{-1}$ and the ferromagnetic one at 118.7 cm$^{-1}$, while the $A_{1g}^{1}$ frequency changes little with spin state. Experimentally, the $E_{2g}^{2}$ mode at 126.0 cm$^{-1}$ softens under pressure and hardens on cooling, opposite to what bond compression predicts, which the paper attributes to pressure weakening spin correlations. Below the 360 K magnetic ordering temperature, both the phonon energy and FWHM of $E_{2g}^{2}$ depart from the anharmonic phonon-decay model, while the FWHM of $A_{1g}^{1}$ does not; using $\omega \approx \omega_0 + \lambda \langle S_i \cdot S_j \rangle$ with $\langle S_i \cdot S_j \rangle \approx 0.31$ at 300 K and $\Delta\omega = 0.25$ cm$^{-1}$ gives $\lambda \approx 0.81$ cm$^{-1}$. The paper thereby positions the $E_{2g}^{2}$ mode as a sensitive Raman probe of magnetic order at room temperature.

Load-bearing premise

The room-temperature coupling strength stands on the assumption that the ~0.25 cm$^{-1}$ deviation of the $E_{2g}^{2}$ mode from the anharmonic fit below $T_c$ is caused by spin-phonon coupling and not by experimental scatter, fitting freedom, or magnetostriction; the paper gives no error bars on the Raman peak positions.

Editorial extensions

If this is right

The $E_{2g}^{2}$ Raman mode can act as a local, contactless probe of magnetic order in Fe3GaTe2 at room temperature.
Because the FWHM also deviates below $T_c$, phonon lifetimes shorten when spin order sets in, implying thermal conductivity and hot-carrier relaxation should change across the magnetic transition.
The mode reassignment changes how future Raman studies of Fe3GaTe2 interpret strain, pressure, and temperature shifts.
The 7.6 GPa inflection in both phonon frequencies and linewidths, if it marks an isostructural transition, gives a pressure window in which magnetic and lattice properties can be tuned together.
Spin-phonon coupling at 300 K means spintronic devices built on Fe3GaTe2 must treat lattice vibrations as a feedback channel for spins, not only as heat.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

A strict reading of the numbers leaves an open consistency check: the first-principles-derived 0 K coupling (about 21.7 cm$^{-1}$) and the 300 K Raman-derived value (about 0.81 cm$^{-1}$) use different magnetizations and different baselines; reconciling them would require a strongly temperature-dependent coupling or a nonlinear dependence on the spin-spin correlation, neither of which the paper ad
The same analysis could be applied to other van der Waals ferromagnets: those whose Raman-active modes show linewidth anomalies below their magnetic ordering temperatures would be candidates for detectable spin-phonon coupling.
If the deviation is truly spin-phonon coupling, sweeping a magnetic field through the transition should shift the $E_{2g}^{2}$ mode energy and linewidth continuously; this is a testable prediction independent of pressure.
Pressure data imply strain engineering can tune spin-phonon coupling in this material, which could be used to adjust spin-lattice relaxation in devices.

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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Desk Editor's Note

read the letter

Dear colleague,

What you should know: this is a solid, workmanlike Raman study of Fe3GaTe2 with a revised mode assignment, and a headline spin-phonon claim that does not hold up against the paper's own numbers. The experimental dataset is real and useful; the central interpretation is not.

The genuinely new parts are the pressure-dependent Raman up to 19.5 GPa and the temperature series from 80 to 690 K, combined with DFT phonon calculations. The reassignment of the 126.0 cm-1 peak to E2g^2 and 143.5 cm-1 to A1g^1 is well argued: the calculated frequencies, the pressure response (E2g^2 softens, A1g^1 stiffens), and the displacement patterns all line up. The distinction between anharmonic and quasi-harmonic behavior is reasonable, and the excitation-power stability check is a nice touch. The methodological detail is enough to reproduce the work.

The soft spot is the room-temperature spin-phonon coupling claim. The observed deviation from the anharmonic model is 0.25 cm-1, and no error bars are reported for the peak positions, so the effect is tiny relative to the scatter you would expect. More damning is the internal inconsistency in SI Note 1. Using the same linear model omega = omega0 + lambda , the authors get lambda ~ 21.7 cm-1 at 0 K from DFT and lambda ~ 0.81 cm-1 at 300 K from experiment. If lambda is a material constant, the predicted 300 K shift would be about 6.7 cm-1, not 0.25 cm-1. The paper never addresses this factor-of-27 discrepancy. That is not a minor issue; it means the headline claim is unsupported. The authors also cannot rule out magnetostriction as the cause of the E2g^2 deviation, especially since they invoke magnetostriction to explain the A1g^1 energy deviation while rejecting spin-phonon there because the FWHM does not deviate. That asymmetry is suggestive, but with the lambda inconsistency it is not convincing.

Who is this for? People working on Raman and lattice dynamics of vdW magnets. The pressure and temperature data are valuable, and the mode assignment is likely to be cited. The spin-phonon section should be rewritten or removed. A serious referee could force a more careful analysis. I would send it to review, not desk reject, but I would expect major revision. I would also be happy to discuss it in a reading group as an example of how internal consistency checks can sink a claim.

Referee Report

3 major / 5 minor

Summary. The manuscript reports a combined Raman spectroscopy and first-principles study of the van der Waals ferromagnet Fe3GaTe2. Pressure-dependent Raman measurements from ambient to 19.5 GPa and temperature-dependent measurements from 80 K to 690 K are used to assign the two observed Raman peaks at 126.0 cm-1 and 143.5 cm-1 to the E2g^2 and A1g^1 modes, respectively. The authors argue that the E2g^2 mode is anharmonic on the basis of its negative Grüneisen parameter, while the A1g^1 mode is quasi-harmonic. The central claim is the observation of room-temperature spin-phonon coupling with a strength of ~0.81 cm-1 at 300 K, inferred from deviations of the E2g^2 phonon energy and FWHM from an anharmonic model below the Curie temperature Tc ~ 360 K.

Significance. If substantiated, a room-temperature spin-phonon coupling in a van der Waals ferromagnet would be a notable result, and the broad pressure-temperature Raman dataset combined with DFT phonon dispersions would be a useful reference for Fe3GaTe2. The manuscript has clear strengths: the systematic experimental coverage, the explicit mode assignment supported by both calculations and pressure trends, and the transparent presentation of the extraction procedure in the Supporting Information. However, the central quantitative claim is not supported by the evidence as presented, because the extracted spin-phonon coupling strengths at 0 K and 300 K are mutually inconsistent under the model used, and the size of the claimed anomaly is not accompanied by any uncertainty estimate.

major comments (3)

[SI Note 1] SI Note 1, Eqs. (S1)–(S3): Under the linear model ω ≈ ω0 + λ<S_i·S_j>, the 0 K DFT-derived value λ ≈ 21.7 cm-1 (from Δω = 20.4 cm-1 and <S_i·S_j> ≈ 0.94) and the 300 K experimental value λ ≈ 0.81 cm-1 (from Δω = 0.25 cm-1 and <S_i·S_j> ≈ 0.31) are inconsistent by a factor of about 27. The same model predicts a spin-phonon shift at 300 K of λ<S_i·S_j> ≈ 6.7 cm-1, not the observed 0.25 cm-1. The manuscript does not reconcile this discrepancy; unless λ is shown to be strongly temperature dependent, or the non-magnetic reference state is shown to be an inappropriate ω0, the numerical spin-phonon coupling strength quoted in the abstract is unsupported.
[Main text, 'Finally, we discuss the spin-phonon coupling effect' and Fig. 4] The claim that the E2g^2 phonon energy deviates by 0.25 cm-1 below Tc is made without reporting the uncertainties of the fitted peak positions or the residuals of the anharmonic fit. If the typical fitting error or the scatter in Fig. 4b is comparable to 0.25 cm-1, then the anomaly, and therefore the extracted coupling strength, is not statistically established. Error bars or at least a quantitative statement of the fitting precision are required before this deviation can be attributed to spin-phonon coupling.
[SI Note 1, Eq. (S3)] The approximation <S_i·S_j> ≈ (<μ>/2μB)^2 identifies the measured total magnetic moment with a spin-only nearest-neighbor spin correlator. This is an ad hoc assumption that has not been validated for Fe3GaTe2, and because λ is inversely proportional to this quantity in Eq. (S2), the numerical values 21.7 cm-1 and 0.81 cm-1 are directly conditional on this unvalidated approximation. The authors should either justify this approximation with independent evidence or present the extracted coupling as subject to a large systematic uncertainty.

minor comments (5)

[Throughout] There are several typographical and formatting issues, including 'V ASP' in the Methods section, 'Plank’s constant' in the main text, and the undefined fit function 'Gauss+Lor' in the pressure-dependent analysis; these should be corrected.
[Fig. 4] The fit parameters ω0, A, B, Γ₀, C, and D for the anharmonic model in Eqs. (1) and (2) are not reported; without them it is not possible to assess the quality of the anharmonic fit or the size of the claimed deviations.
[Abstract and Introduction] The phrase 'the first room-temperature spin-phonon coupling in vdW ferromagnet' is an overclaim unless the authors have verified that no prior work on any van der Waals ferromagnet has reported a room-temperature spin-phonon coupling; the wording should be qualified or supported by a literature search.
[Table I] The column headers 'D2 D2 D3 Optb86b Optb86b' are unclear; the reader cannot tell which computational settings correspond to each column without referring to Table S1, so the headers should be made explicit.
[Main text, mode assignment] The statement that the phonon energies 'originate from the anharmonic and harmonic vibration modes' is imprecise; the modes themselves are not anharmonic or harmonic, rather their pressure/temperature behavior is. This wording should be revised.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity; the spin-phonon coupling extraction is a standard residual analysis with independent DFT support.

full rationale

The central derivation chain is not circular. The anharmonic model (Eqs. 1-2) is fit to the high-temperature Raman data above Tc, and the low-temperature deviation of the E2g^2 phonon energy and FWHM from that extrapolated model is then interpreted as spin-phonon coupling. This is a standard null-hypothesis residual analysis: the model is constrained by the paramagnetic region, and the deviation below Tc is observed rather than constructed from the fit. The coupling strength lambda is obtained by dividing the measured deviation Δω = 0.25 cm^-1 at 300 K by the independently measured spin correlation <Si·Sj> ≈ 0.31 from SQUID magnetization; this is a parameter extraction, not a self-fulfilling prediction. The DFT comparison between the non-magnetic (98.3 cm^-1) and ferromagnetic (118.7 cm^-1) E2g^2 phonons is an independent first-principles calculation whose assumptions (choice of magnetic state) are stated and do not use the experimental residual as input. The self-citations (refs 4, 23, 41) provide a review, XRD data, and experimental setup details; none is load-bearing for the main claim. The large discrepancy between the 0 K DFT-derived lambda ≈ 21.7 cm^-1 and the 300 K experimental lambda ≈ 0.81 cm^-1 is an internal consistency and modeling concern, but it does not make the derivation circular. Accordingly, no load-bearing step reduces by construction to its own inputs, and the paper is not circular.

Assumptions & free parameters 3 free parameters · 4 assumptions · 0 invented entities

The central spin-phonon claim rests on a semi-empirical extraction with a crude spin-correlation approximation and an unresolved factor-27 discrepancy with the 0 K DFT value. The anharmonic fit parameters are not reported, and the DFT method is selected post hoc to match experiment.

free parameters (3)

Anharmonic model parameters (omega0, A, B for Eq. 1; Gamma0, C, D for Eq. 2) = not given in text
Fitted to temperature-dependent Raman data to separate anharmonic baseline from spin-phonon deviation; the values are not reported, making it impossible to assess the fit quality or the extrapolation error.
DFT parameter selection (PBE+DFT-D2 finite displacement) = chosen among alternatives
Table S1 shows several calculation settings; the authors chose the one yielding phonon energies closest to experiment, introducing a mild selection bias.
Spin-phonon coupling strength lambda at 300 K = 0.81 cm^-1
Derived as Delta_omega / <Si.Sj> = 0.25 / 0.31; depends on the assumed spin correlation factor and the measured deviation.

assumptions (4)

domain assumption PBE+DFT-D2 approximation gives accurate phonons in Fe3GaTe2
The calculations use GGA-PBE with DFT-D2 vdW correction, selected because it gives the closest match to measured Raman shifts (Table S1); this is a posteriori method selection.
domain assumption The linear model omega = omega0 + lambda * <Si.Sj> applies to E2g^2
Taken from literature (Rudolf et al.), assumes the phonon shift is proportional to the spin correlation function.
ad hoc to paper Spin correlation can be approximated as <Si.Sj> = (<mu>/2*mu_B)^2
This factorized approximation ignores spin fluctuations and is used to convert the average magnetization to a two-spin correlation; it is not derived in the paper.
domain assumption The deviation from the anharmonic model below Tc is due to spin-phonon coupling, not magnetostriction or other effects
For the A1g mode, the energy deviation without FWHM deviation is attributed to magnetostriction, while for E2g both deviations are attributed to spin-phonon coupling; this asymmetry is asserted rather than proven.

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Cite this review

Pith. "Pith review of Lattice dynamics and phonon dispersion of van der Waals layered ferromagnet Fe3GaTe2." pith.science (2026). https://pith.science/paper/NEQ6UBOV

@misc{pith2026241116463,
  author       = {Pith},
  title        = {Pith review of: Lattice dynamics and phonon dispersion of van der Waals layered ferromagnet Fe3GaTe2},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/NEQ6UBOV}},
  note         = {Machine review of arXiv:2411.16463}
}

read the original abstract

Despite the tremendous progress in spintronic studies of van der Waals (vdW) room-temperature ferromagnet Fe3GaTe2, much less effort has been spent on its lattice dynamics and possible interaction with spintronic degrees of freedom. In this work, by combining Raman spectroscopy in a wide range of pressure (atmospheric pressure~19.5 GPa) and temperature (80~690 K) with first-principles calculation, we systematically studied the lattice dynamics and phonon dispersion of Fe3GaTe2. Our results show that the phonon energies of Fe3GaTe2 located at 126.0 cm-1 and 143.5 cm-1 originate from the anharmonic and harmonic vibration modes, respectively. Furthermore, the first room-temperature spin-phonon coupling in vdW ferromagnet is observed with strength of ~0.81 cm-1 at 300 K, by identifying Raman anomalies in both phonon energy and full width at half maximum (FWHM) of below Curie temperature of Fe3GaTe2. Our findings are valuable for fundamental and applied studies of vdW materials under variable conditions.

Figures

Figures reproduced from arXiv: 2411.16463 by the authors.

**Figure 3.** (a) Atomic displacement patterns of the bulk Fe3GaTe2 with ferromagnetic interlayer interaction, where the bright pink, blue, and purple (or pale pink) atoms represent the Te, Ga and Fe atoms, respectively, and the arrows (arrows lengths) represent the vibrational direction (vibrational strength) (left panel). Schematic diagram of changeable atomic structure involving the 𝐸2𝑔 2 and 𝐴1𝑔 1 modes under high pressure (r… view at source ↗

**Figure 4.** (a) Raman spectroscopies of the Fe3GaTe2 at temperatures varying from 80 K to 690 K. Temperature-dependent phonon energies for the (b) 𝐸2𝑔 2 and (c) 𝐴1𝑔 1 modes. Temperature-dependent FWHMs for the (d) 𝐸2𝑔 2 and (e) 𝐴1𝑔 1 modes. The red and blue lines are fitted results using phonon anharmonic processes. value of ~0.31 at 300 K. Derived from the experimental data (Figures 4b and 4c), the value of △ω=ω-ω0 of the 𝐸2𝑔 … view at source ↗

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Works this paper leans on

3 extracted references · 3 canonical work pages

[1]

Spin-phonon coupling in antiferromagnetic chromium spinels

(1) Rudolf, T.; Kant, C.; Mayr, F.; Hemberger, J.; Tsurkan, V .; Loidl, A. Spin-phonon coupling in antiferromagnetic chromium spinels. New J. Phys. 2007, 9,

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Tremendous tunneling magnetoresistance effects based on van der Waals room -temperature ferromagnet Fe3GaTe2 with highly spin-polarized Fermi surfaces

(4) Li, X.; Zhu, M.; Wang, Y .; Zheng, F.; Dong, J.; Zhou, Y .; You, L.; Zhang, J. Tremendous tunneling magnetoresistance effects based on van der Waals room -temperature ferromagnet Fe3GaTe2 with highly spin-polarized Fermi surfaces. Appl. Phys. Lett. 2023, 122, 082404

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Strong spin-phonon coupling in two-dimensional magnetic semiconductor CrSBr

(2) Xu, X.; Wang, X.; Chang, P.; Chen, X.; Guan, L.; Tao, J. Strong spin-phonon coupling in two-dimensional magnetic semiconductor CrSBr. J. Phys. Chem. C 2022, 126, 10574. (3) Kozlenko, D. P.; Lis, O. N.; Kichanov, S. E.; Lukin, E. V .; Belozerova, N. M.; Savenko, B. N. Spin -induced negative thermal expansion and spin -phonon coupling in van der Waals m...

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Pith tools

Reviewed August 12, 2026 · model on record in the stance chip above.

[1] [1]

Spin-phonon coupling in antiferromagnetic chromium spinels

(1) Rudolf, T.; Kant, C.; Mayr, F.; Hemberger, J.; Tsurkan, V .; Loidl, A. Spin-phonon coupling in antiferromagnetic chromium spinels. New J. Phys. 2007, 9,

work page 2007

[2] [19]

Tremendous tunneling magnetoresistance effects based on van der Waals room -temperature ferromagnet Fe3GaTe2 with highly spin-polarized Fermi surfaces

(4) Li, X.; Zhu, M.; Wang, Y .; Zheng, F.; Dong, J.; Zhou, Y .; You, L.; Zhang, J. Tremendous tunneling magnetoresistance effects based on van der Waals room -temperature ferromagnet Fe3GaTe2 with highly spin-polarized Fermi surfaces. Appl. Phys. Lett. 2023, 122, 082404

work page 2023

[3] [76]

Strong spin-phonon coupling in two-dimensional magnetic semiconductor CrSBr

(2) Xu, X.; Wang, X.; Chang, P.; Chen, X.; Guan, L.; Tao, J. Strong spin-phonon coupling in two-dimensional magnetic semiconductor CrSBr. J. Phys. Chem. C 2022, 126, 10574. (3) Kozlenko, D. P.; Lis, O. N.; Kichanov, S. E.; Lukin, E. V .; Belozerova, N. M.; Savenko, B. N. Spin -induced negative thermal expansion and spin -phonon coupling in van der Waals m...

work page 2022