{"id":"bf6969b5-e1a7-4d80-b2c4-293acb244a00","arxiv_id":"2501.13602","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"A temperature-independent anomalous in-plane Hall conductivity of about 0.8 S/cm is observed between 100 and 300 K in spin-canted epitaxial Fe3Sn films and attributed to Weyl-point Berry curvature.","lead":"Tilted iron moments in thin films of the kagome metal Fe3Sn produce a Hall voltage when the magnetic field lies in the sample plane, and the effect persists up to room temperature. A nearby magnetic layer can make the voltage about 38% larger.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Thickness-scaling evidence for bulk spin canting is internally inconsistent: Fig. 4(d) gives V60/V30 = 2.9/7.4 ≈ 0.39, not the quoted 2.5, and the scaling test cannot distinguish a fixed-interface source from a bulk source in parallel conduction.","rationale":"The reader identified the bulk-uniform nature of the out-of-plane canting Mz as the weakest load-bearing premise. My stress-test agrees with that identification, but the more concrete and checkable flaw is in the one experiment offered to support it: the thickness scaling argument in the section 'Origin of the in-plane Hall effect.' The quoted ratio contradicts the plotted fitted amplitudes, and the stated physical reasoning ('independence of thickness for an interfacial effect') is not the correct expectation for a fixed-thickness source in a parallel-conducting film stack. This matters because, without a reliable bulk-versus-interface discrimination, the symmetry-breaking step that turns a MztT-preserving state into one with finite in-plane Berry curvature is not established. The rest of the paper — the 2π-periodicity, the B-antisymmetrization, and the temperature-independent plateau — is coherent and not internally contradicted, but it inherits this premise. My recommendation is to keep the CONDITIONAL verdict: the concern does not prove the effect is absent, but it identifies a specific, correctable flaw in the evidence chain. I would not move to accept as is, nor reject outright, because the underlying data might survive a corrected analysis. The largest unresolved issue is whether the thickness test, once correctly posed, can distinguish the scenarios within experimental error; the current two-point dataset likely cannot.","tokens_in":15105,"tokens_out":15131,"duration_ms":148909,"concrete_test":"Correct the thickness analysis by re-deriving VIPHE(d1)/VIPHE(d2) for (i) uniform bulk canting, (ii) a fixed-thickness interface layer in parallel with the bulk, and (iii) an interface layer whose thickness scales with film thickness, using the actual circular Hall bar geometry and the Pt-shunt corrections already outlined in Sec. III of the Supplementary Materials. Then check the Fig. 4(d) amplitudes (2.9 ± 0.1 and 7.4 ± 0.2 µV) against the corrected ratio. If the quoted interfacial scenario is not expected to give a thickness-independent voltage, and if the measured ratio lies between the bulk prediction (2) and the fixed-interface prediction (4), the paper must provide a longer thickness series with error bars or retract the claim that the bulk-canting origin is experimentally established.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The claim that the anomalous IPHE arises from uniform bulk spin canting rests on the thickness test in Fig. 4(d) excluding interfacial Dzyaloshinskii-Moriya canting. As written, the argument contains a clear internal inconsistency: the text states “we find VIPHE(60 nm)/VIPHE(30 nm) ≈ 2.5,” but the fitted amplitudes are VIPHE(60 nm) = (2.9 ± 0.1) µV and VIPHE(30 nm) = (7.4 ± 0.2) µV, so the ratio is 2.9/7.4 ≈ 0.39, not 2.5. The accompanying statement that “VIPHE scales approximately with the thickness” is also opposite to the uniform-bulk expectation VIPHE ∝ 1/d for fixed bias current. More importantly, the test does not cleanly separate the alternatives: in a parallel-conduction stack, a fixed-thickness interface source gives VIPHE ∝ 1/d², predicting V30/V60 ≈ 4 for d60/d30 = 2, while uniform bulk gives V ∝ 1/d, predicting V30/V60 ≈ 2. The measured ratio 2.55 is intermediate between these predictions, and an interface layer whose thickness scales with total film thickness would reproduce the bulk ratio. Therefore, the thickness data, as reported, cannot establish that the measured Mz ≈ 0.11 µB/Fe corresponds to a bulk uniform canting that breaks the MztT magnetic glide symmetry, which is the central premise for the topological IPHE interpretation.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript reports molecular-beam-epitaxial growth of Fe3Sn(001) films on Pt(111)/sapphire, fabrication of circular Hall bars, and measurements of the in-plane Hall response at 300 K. By antisymmetrizing the transverse resistivity in B∥, the authors isolate a 2π-periodic, B-antisymmetric in-plane Hall resistivity ρ_IPHE(ϕ,θ), separate it from the symmetric planar-Hall and STR contributions, and find the amplitude to be nearly field-independent below 100 mT, temperature-independent between 100 and 300 K with |σ0_IPHE| ≈ 0.8 S/cm, and roughly consistent with the film thickness. They interpret the effect as an anomalous IPHE driven by Weyl-point Berry curvature enabled by an out-of-plane canting Mz ≈ 0.11 μB/Fe that breaks the MztT magnetic-glide symmetry, and they report a ≈38% enhancement in a Fe3Sn/Al2O3/CoFeB heterostructure. DFT/Wannier calculations with a canted magnetization and a Zeeman term yield a 2π-periodic σ_IPHE(α) of order 1.5 S/cm.","tokens_in":15356,"tokens_out":9032,"duration_ms":81561,"significance":"If established, the result would be the first room-temperature, temperature-independent anomalous in-plane Hall effect from topological electronic states, with a plausible design paradigm for tuning it. The paper is commendable for its angle-resolved circular-Hall-bar methodology, the explicit separation of symmetric and antisymmetric responses, and the internal checks of field independence and thickness scaling. However, the theoretical calculation is not parameter-free, and the experimental identification of a uniform bulk canting rests on indirect evidence; these issues must be resolved before the central claim can be accepted.","major_comments":[{"comment":"The central theoretical claim is not parameter-free. In the effective Hamiltonian H = H0 + gB∥·σ, the authors insert a canting M = (1, 0, 0.1) and choose gB∥ = 0.001 eV; since this canting breaks MztT by construction, the resulting nonzero σ_IPHE is guaranteed by symmetry (the authors themselves state that σ_IPHE vanishes without canting). Therefore the statement in the 'Origin' section that |σ0_IPHE| ≈ 0.8 S/cm is in 'relatively good quantitative agreement' with |σcalc_IPHE| ≈ 1.5 S/cm is not a meaningful test unless the authors show the sensitivity to the canting angle, the effective g, and the chemical potential. I request a parameter-dependence study or a fully ab initio calculation with the experimental Mz as the only input, and a discussion of whether the calculated value is robust.","section":"Methods, 'Anomalous in-plane Hall effect calculated using the Wannier tight-binding model'"},{"comment":"The thickness-scaling argument as written is internally inconsistent and does not establish a bulk origin. The text states VIPHE(60 nm)/VIPHE(30 nm) ≈ 2.5 and that 'VIPHE scales approximately with the thickness of the film,' but the fitted amplitudes in the same paragraph and Fig. 4(d) are (2.9 ± 0.1) µV and (7.4 ± 0.2) µV, so the ratio is 2.9/7.4 ≈ 0.39, not 2.5. For a uniform bulk ρ_IPHE at fixed bias current, the transverse voltage scales as V ∝ 1/d, so the measured V30/V60 ≈ 2.55 is actually consistent with a bulk effect; however, the quoted ratio reverses this conclusion. Moreover, the test cannot cleanly exclude a fixed-thickness interface source in a parallel-conduction geometry, whose scaling prediction is separated from the bulk prediction by only a factor of two, and an interface layer whose thickness scales with the total film thickness would reproduce the bulk ratio. The authors should re-analyze the thickness data with a proper current-distribution model and state the actual fitted ratio.","section":"Fig. 4(d) and 'Origin of the in-plane Hall effect'"},{"comment":"The only direct evidence for the out-of-plane canting is the remanent Mz ≈ 0.11 μB/Fe in Fig. 2(c). The inference that this reflects a uniform bulk canting (rather than a near-interface Dzyaloshinskii-Moriya canting, a small population of misaligned domains, or an extrinsic surface moment) is based on the thickness scaling discussed above and on the bulk-like resistivity; it is not conclusive. Since the entire symmetry argument for the topological IPHE requires that MztT be broken by the bulk magnetic structure, the authors need either direct magnetic-structure determination (they themselves note that neutron scattering on bulk crystals is needed) or additional transport tests that distinguish bulk from interface canting, such as a Hall signal scaling with total magnetic moment versus interface area.","section":"Experimental detection of spin-canted ferromagnetism, Fig. 2(c)"},{"comment":"The temperature independence of σ_IPHE between 100 and 300 K is presented as the key evidence for an intrinsic Berry-curvature mechanism, but it is shown at a single field and angle (B∥ = 50 mT, ϕ = π, θ = π/2). The authors invoke a magnetic-field-misalignment orbital Hall contribution to explain the growth of the IPHE for B∥ ≥ 100 mT; because this same misalignment is present at lower fields, the analysis should demonstrate that the 50 mT data used for the temperature dependence lie in a regime where this orbital contribution is negligible at all temperatures, not only at 300 K. For example, measuring σ_IPHE(T) at several B∥ below 100 mT and confirming identical plateaus would make the intrinsic-origin claim more robust.","section":"Fig. 4(b) and 'Origin of the in-plane Hall effect'"}],"minor_comments":[{"comment":"The data availability statement contains the placeholder 'link XXX'; the actual deposition link should be provided before publication.","section":"Data availability statement"},{"comment":"The cross-reference 'c.f. Fig. 1(c)' should refer to Fig. 2(c), where the magnetization measurements are shown.","section":"Experimental detection section"},{"comment":"The phrase 'hysteresis in both the orbital Hall and magnetization measurements' is confusing; the out-of-plane Hall resistivity is the conventional Hall effect, not the orbital Hall effect, which is introduced later as a distinct mechanism.","section":"Experimental detection section"},{"comment":"The caption reads 'Shown is a the θ dependence'; it should read 'Shown is the θ dependence.'","section":"Fig. 5(e) caption"},{"comment":"The phrase 'topological heterostructure structure' should read 'topological heterostructure.'","section":"Heterostructure section"}],"recommendation":"major_revision","confidential_remarks":"To the editor: The paper addresses a timely and potentially high-impact observation. My main concern is that the two load-bearing pillars—the parameter-free nature of the calculation and the bulk-canting identification—are not yet solid. The thickness-scaling error in the text is the most concrete fixable problem; the actual data may even support the bulk interpretation if analyzed correctly. I recommend major revision rather than rejection, provided the authors can supply a corrected scaling analysis and a parameter-dependence study of σ_IPHE, and ideally additional magnetic characterization."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Dear —,\n\nThis paper reports the first room-temperature, temperature-independent anomalous in-plane Hall effect attributed to topological Weyl points, in epitaxial Fe3Sn films, with a 38% enhancement when a CoFeB layer is added. The observation itself looks credible: the circular Hall bar geometry cleanly separates the B-antisymmetric IPHE from the planar Hall and symmetric transverse resistivity contributions, and the 2π periodicity plus field-independence below 100 mT are good internal consistency checks. The symmetry argument that out-of-plane canting breaks the MztT glide symmetry and permits a finite σxy is coherent.\n\nThe soft spots are real and one of them is load-bearing. The thickness-scaling test in Fig. 4(d) is internally inconsistent: the text claims VIPHE(60)/VIPHE(30) ≈ 2.5, but the reported fitted amplitudes are 2.9 and 7.4 µV, which gives 0.39. And the expected scaling for a bulk source at fixed current is VIPHE ∝ 1/d, so a thicker film should show a smaller voltage, not a larger one. The test also cannot separate a bulk source from a fixed interface source in a parallel-conduction stack, because the two scenarios predict ratios of 2 and 4, and the measured ratio sits between. So the thickness data do not establish bulk canting—the central premise for the topological interpretation. The authors concede that neutron scattering is needed, which is honest but undercuts the claim. The DFT/Wannier calculation is also not parameter-free: it inserts the canting ratio and the Zeeman scale, so the factor-of-two agreement with experiment is a demonstration of the symmetry principle, not a quantitative prediction. Finally, there are no error bars on the temperature dependence of σIPHE, no supplementary file, and the data availability link is a placeholder.\n\nI agree with the reader's conditional verdict, and I'd put the thickness problem at the top of the referee list. None of this kills the observation, but the bulk topological origin is not yet established. The paper deserves a serious referee—an editor should send it out—but it will need substantial revision. I would not yet cite it as evidence for a topological IPHE in my own work.","headline":"A credible room-temperature in-plane Hall effect in Fe3Sn, but the bulk topological origin is undercut by an internal inconsistency in the thickness-scaling argument.","tokens_in":16024,"tokens_out":3775,"would_cite":false,"duration_ms":30391,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":["75.47.-m","72.15.Gd","75.70.-i"],"model":"deepseek-v4-flash","headline":"A spin-canted kagome Weyl ferromagnet, Fe3Sn, exhibits an anomalous in-plane Hall effect at room temperature whose temperature-independent magnitude across 100–300 K identifies it as an intrinsic Berry-curvature response.","keywords":["anomalous in-plane Hall effect","Weyl ferromagnet","Fe3Sn","kagome lattice","Berry curvature","spin canting","molecular beam epitaxy","topological heterostructure"],"falsifier":"A neutron diffraction experiment on bulk Fe3Sn crystals or on a sufficiently thick film that finds no out-of-plane component of the ordered magnetic moment below the ordering temperature would directly falsify the symmetry-breaking premise; alternatively, measuring the same in-plane Hall protocol on a sample with a verified strictly in-plane magnetization and zero remanent out-of-plane moment should show no 2π-periodic field-antisymmetric signal if the proposed mechanism is the only source.","tokens_in":14810,"feed_emoji":"🧲","tokens_out":8569,"duration_ms":70829,"temperature":0.7,"pith_summary":"The paper tries to establish that the kagome-lattice Weyl ferromagnet Fe3Sn, grown as epitaxial thin films, shows a genuine anomalous in-plane Hall effect at room temperature: a transverse voltage that is odd under reversal of the in-plane magnetic field and that does not require a magnetic field along the sample normal. The effect is attributed to a small out-of-plane canting of the iron magnetic moments, about 0.11 Bohr magneton per Fe atom, which breaks a magnetic glide-mirror symmetry and lets Weyl-point Berry curvature produce a nonzero in-plane Hall conductivity. The signature is a temperature-independent conductivity plateau between 100 and 300 K with magnitude around 0.8 S/cm, close to the calculated value of about 1.5 S/cm, and the amplitude grows by roughly 38% when a CoFeB layer is placed nearby. If true, this is the first room-temperature, temperature-independent anomalous in-plane Hall effect from topological electronic states, opening a route to magnetic sensors and spintronic devices that operate without cryogenic cooling. The paper supports the claim with symmetry analysis, ab initio calculations, angle-resolved Hall measurements on circular devices, thickness scaling, and a heterostructure control experiment.","feed_headline":"Anomalous in-plane Hall effect observed at 300 K in a Weyl ferromagnet","feed_subtitle":"Temperature-independent signal from 100 to 300 K points to Berry curvature of Weyl points in Fe3Sn films.","key_machinery":"The load-bearing symmetry is the magnetic glide-mirror operation combining an out-of-plane mirror, a fractional translation, and time reversal; when the magnetization lies strictly in the plane, this symmetry forces the Berry curvature to integrate to zero, while an out-of-plane canting Mz breaks it and permits a finite Berry curvature and thus a finite anomalous in-plane Hall effect. The experimental machinery is a circular Hall bar that allows the full 2π angle dependence of the transverse resistivity to be decomposed into a field-antisymmetric in-plane Hall effect, a symmetric planar Hall effect, and a symmetric transverse resistivity, isolating the true Hall signal from artefacts. The temperature independence of the extracted conductivity serves as the fingerprint that the signal is intrinsic (Berry-curvature) rather than extrinsic (skew scattering or side jumps).","core_discovery":"The central claim is that Fe3Sn thin films with in-plane ferromagnetism and a finite out-of-plane spin canting exhibit an anomalous in-plane Hall effect whose magnitude is independent of temperature between 100 and 300 K, which the authors identify as the hallmark of an intrinsic Berry-curvature contribution from Weyl points near the Fermi energy. In an uncanted ferromagnet with magnetization along the x direction, the magnetic space group contains a glide-mirror operation that enforces cancellation of the Berry curvature, so the in-plane Hall conductivity vanishes. A canting along z breaks this operation and makes the total Berry curvature finite, producing an in-plane Hall conductivity of about 0.8 S/cm, in reasonable agreement with the calculated value. A circular 12-terminal Hall bar that rotates the current direction relative to the in-plane field reveals the predicted 2π-periodic modulation, a π shift between opposite current directions, and a negligible ordinary anomalous Hall offset; thickness scaling indicates the effect comes from the bulk of the film rather than the interface. Adding a CoFeB layer with a stray-field component along z increases the measured amplitude by roughly 38%, demonstrating external control of the effect.","pith_inferences":["The same symmetry-breaking logic likely applies to other magnetic Weyl systems with easy-plane anisotropy and a tunable canted moment, making Fe3Sn a first member of a broader family rather than an isolated case.","If neutron scattering confirms the bulk canting, the temperature-independent in-plane Hall plateau could serve as a sensitive probe of the canting angle, because the conductivity should scale with Mz in the small-canting limit.","The heterostructure demonstration is only a proof of concept; optimizing the spacer thickness and the stray-field geometry could push the enhancement well beyond 38%, and the same mechanism might also tune the nonlinear Hall effect in these films.","One caution follows from the authors' own note: the magnetic structure is not yet measured directly, so the precise quantitative link between the canting moment and the measured conductivity remains to be established by a microscopic probe rather than inferred from transport alone."],"forward_implications":["If the claim is correct, topological Hall effects no longer need cryogenic temperatures: kagome magnets with large exchange interactions can deliver Berry-curvature Hall signals at and above 300 K.","The circular Hall bar with full angle decomposition provides a template for separating true in-plane Hall effects from planar-Hall and misalignment artefacts, which can be applied to other candidate materials.","The 38% enhancement by a CoFeB stray field demonstrates a practical route to tune the in-plane Hall amplitude in a topological heterostructure, suggesting that magnetic stray fields from adjacent layers can serve as a control knob.","A temperature-independent in-plane Hall conductivity between 100 and 300 K can be used as a fast diagnostic for intrinsic topological contributions in future materials.","The symmetry rule, to break the out-of-plane glide-mirror operation via canting, becomes a design criterion: canted kagome ferromagnets with strong exchange are candidate room-temperature in-plane Hall materials."],"supporting_citations":[{"why":"Reports the Weyl points near the Fermi energy in Fe3Sn that the measured in-plane Hall effect is attributed to.","marker":"[20]"},{"why":"Supplies the large exchange interaction J ≈ 40 meV that keeps Berry-curvature effects observable at room temperature.","marker":"[19]"},{"why":"Predicted the anomalous in-plane Hall effect and its symmetry requirements, which the experiment directly targets.","marker":"[14]"},{"why":"Provides the theoretical framework connecting in-plane Hall conductivity to Berry curvature under broken magnetic symmetries.","marker":"[15]"},{"why":"Defines the intrinsic Berry-curvature contribution to the anomalous Hall effect and its temperature-independence signature, used to classify the observed plateau.","marker":"[1]"},{"why":"Describes the interface-induced spin-canting mechanism that the thickness-scaling test is used to exclude.","marker":"[36]"},{"why":"Provides magnetization behavior of Fe3Sn used to benchmark the thin-film moments and identify the out-of-plane canting component.","marker":"[28]"}],"fun_headline_variants":["Weyl ferromagnet yields room-temp in-plane Hall effect","In-plane Hall effect from Weyl points at 300 K","Fe3Sn films show Weyl-driven Hall effect at room temp","Room-temp anomalous Hall effect in Weyl ferromagnet","Weyl points trigger in-plane Hall effect in Fe3Sn"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The argument stands on the premise that the tiny out-of-plane remanent moment measured in the films, about 0.11 Bohr magneton per iron atom, is a uniform tilt of the magnetic moments through the bulk of the film, rather than an interface-only effect or a measurement artefact, because only a bulk tilt breaks the symmetry that the transport claim requires.","fun_headline_variants_meta":{"raw":{"variants":["Weyl ferromagnet yields room-temp in-plane Hall effect","In-plane Hall effect from Weyl points at 300 K","Fe3Sn films show Weyl-driven Hall effect at room temp","Room-temp anomalous Hall effect in Weyl ferromagnet","Weyl points trigger in-plane Hall effect in Fe3Sn"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000503,"raw_usage":{"total_tokens":2500,"prompt_tokens":1034,"completion_tokens":1466,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":650,"completion_tokens_details":{"reasoning_tokens":1376}},"tokens_in":650,"tokens_out":1466,"duration_ms":9719,"temperature":1.0,"reasoning_tokens":1376,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-10T15:47:20.603773+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A neutron diffraction experiment on bulk Fe3Sn crystals or on a sufficiently thick film that finds no out-of-plane component of the ordered magnetic moment below the ordering temperature would directly falsify the symmetry-breaking premise; alternatively, measuring the same in-plane Hall protocol on a sample with a verified strictly in-plane magnetization and zero remanent out-of-plane moment should show no 2π-periodic field-antisymmetric signal if the proposed mechanism is the only source.","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Reports the Weyl points near the Fermi energy in Fe3Sn that the measured in-plane Hall effect is attributed to."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Supplies the large exchange interaction J ≈ 40 meV that keeps Berry-curvature effects observable at room temperature."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Provides the theoretical framework connecting in-plane Hall conductivity to Berry curvature under broken magnetic symmetries."},{"cited_title":"Hellman, A","cited_arxiv_id":null,"evidence_quote":"Describes the interface-induced spin-canting mechanism that the thickness-scaling test is used to exclude."},{"cited_title":"Prodan, D","cited_arxiv_id":null,"evidence_quote":"Provides magnetization behavior of Fe3Sn used to benchmark the thin-film moments and identify the out-of-plane canting component."}],"review_version":1}