{"id":"54d3aeee-89ea-4044-a0fc-260d35e8771f","arxiv_id":"2603.25878","paper_version":2,"verdict":"ACCEPT","confidence":"HIGH","novelty_score":6.0,"correctness_risk":"low","formal_verification":"none","parameter_count":4,"one_line_summary":"Bulk NaMnAs shows a doubly degenerate k=0 AFMR mode at 7 meV that softens but remains clear up to 295 K, yielding single-ion anisotropy D ≈ 0.1–0.2 meV.","lead":"THz spectroscopy detects a 7 meV antiferromagnetic resonance in bulk NaMnAs that stays visible to room temperature and confirms easy-axis order along the c-axis. The result supplies a concrete room-temperature AF semiconductor platform for magnonics and THz devices.","discovery_kind":"extension","skeptic_critique":{"model":"grok-4.5","headline":"No significant objection identified","rationale":"The paper’s primary result is the observation and field/temperature characterization of the AFMR mode itself. The data in Faraday and Voigt geometries match the classic easy-axis formulas without adjustable parameters beyond g and ω₀, the mode stays clear of phonons, and it is still resolved at 295 K. The anisotropy extraction is presented only as a rough estimate (explicitly “order-of-magnitude”) and is corroborated by an independent DFT route that yields a comparable D. Because the reader already isolates this secondary approximation and correctly judges that it does not threaten the spectroscopic claim, no further load-bearing concern arises. The recommended verdict therefore remains ACCEPT.","tokens_in":13321,"tokens_out":595,"duration_ms":6261,"concrete_test":"Re-fit the B∥c branch positions in Fig. 3c and the B⊥c branch in Fig. 4b with free g and ω₀; confirm that the zero-field intercept remains 7.0 ± 0.2 meV and that the two independent g values stay consistent with 2.0 within the stated errors. If either fails, the mode assignment would need re-examination.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim is spectroscopic: a single AFMR line at 7.0 ± 0.2 meV (B = 0) that splits linearly for B∥c (g≈ 1.99) and blueshifts as √(ω₀^{2} + (gμ B)²) for B⊥c, remaining visible to 295 K while softening to 5.4 meV. This pattern is textbook easy-axis AFMR (Kittel formulas 1–2) and is independent of the secondary D estimate. The reader correctly flags that D ≈ 0.1–0.2 meV rests on a mean-field J1 ≈ 4 meV from TN ≈ 350 K plus neglect of other J’s (Eqs. 4–5), but the paper itself labels this an order-of-magnitude estimate, cross-checks it against DFT (Table I, D = 0.1 meV), and does not rest the identification of the mode or the room-temperature visibility on the precise value of D. No internal inconsistency or data-quality issue undermines the strongest claim.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.5","summary":"The manuscript reports frequency-domain THz magneto-transmission experiments on bulk tetragonal NaMnAs crystals. At B = 0 a single resonance is observed at 7.0 ± 0.2 meV; it splits linearly with g≈ 1.99 when B is applied along the tetragonal axis and blueshifts as √(ω₀^{2} + (gμ_B B)^{2}) when B is perpendicular, remaining visible (while softening to 5.4 meV) up to 295 K. These field and temperature dependences are identified with the doubly degenerate k = 0 magnon of an easy-axis C-type antiferromagnet whose Néel vector lies along the c axis, thereby confirming earlier DFT predictions. A rough estimate of the single-ion anisotropy D ≈ 0.1–0.2 meV is extracted from the zero-field gap together with a mean-field J1 derived from TN ≈ 350 K; supporting phonon DFT and exchange calculations are also presented.","tokens_in":13616,"tokens_out":889,"duration_ms":21030,"significance":"If the spectroscopic identification holds, the work supplies a clean, textbook example of room-temperature easy-axis AFMR in an exfoliable layered semiconductor whose magnon gap lies in the technologically relevant THz window. The data sets (Faraday and Voigt geometries, absolute transmission, and a dense temperature series) are of high quality and match Kittel’s formulas without adjustable parameters beyond g ≈ 2. The phonon DFT (U = 5 eV) reproduces the observed IR bands, and the linear-spin-wave dispersion calculated from the extracted exchanges offers a concrete, falsifiable prediction for future inelastic neutron scattering. These strengths make the paper a useful addition to the still-small catalogue of ambient-temperature antiferromagnetic semiconductors.","major_comments":[],"minor_comments":[{"comment":"Abstract and first paragraph of Sec. III: the word “antiferromanetic” is misspelled (missing “g”).","section":null},{"comment":"Section headings contain spurious spaces (“EXPERIMENT AL DET AILS”, “EXPERIMENT AL RESUL TS AND DISCUSSION”, “THEORETICAL MODELLING”). These should be corrected for production.","section":null},{"comment":"Fig. 2 caption and main text: the multi-phonon feature is labeled “P” while the symmetry labels Eu/A2u follow space group 129; a brief note that DFT finds a weakly lowered symmetry (No. 115) would avoid reader confusion.","section":null},{"comment":"Eqs. (4)–(5) and the subsequent D estimate: the text already calls the result an order-of-magnitude figure, yet the abstract quotes a numerical range 0.1–0.2 meV. Adding a one-sentence caveat that the range reflects both the mean-field J1 uncertainty and the DFT cross-check would make the claim more precise.","section":null},{"comment":"Fig. 9 and surrounding text: the ad-hoc 3/4 temperature rescaling of the mean-field ω_Γ curve is stated but not motivated. A short remark that the factor compensates for the well-known mean-field overestimate of TN would improve transparency.","section":null},{"comment":"Reference [39] (data availability) is incomplete; a DOI or repository link should be supplied.","section":null}],"recommendation":"minor_revision","confidential_remarks":"The experimental core is solid and the paper is essentially ready; the only reason I chose minor_revision rather than accept is the accumulation of easily fixed typos and the slightly over-precise wording of the D range in the abstract. No novelty or citation concerns."},"author_rebuttal":null,"desk_editor":{"model":"grok-4.5","letter":"This is the first THz magneto-transmission study of bulk NaMnAs. They see a single zero-field line at 7.0 ± 0.2 meV that splits linearly for B parallel to c (g ≈ 1.99) and blueshifts as the square-root form for B perpendicular, remaining visible to 295 K while softening to 5.4 meV. That pattern is textbook easy-axis AFMR and confirms the DFT prediction that the Néel vector lies along the tetragonal axis. The data themselves—Faraday and Voigt geometries, absolute transmission, temperature series—are clean and match Kittel’s formulas without forcing.\n\nWhat is new is therefore the spectroscopic observation itself plus the experimental bound on single-ion anisotropy. Prior work had magnetization, neutron diffraction and DFT; none of the AFMR numbers or the room-temperature visibility of the k = 0 mode were measured. Phonon DFT (U = 5 eV chosen to match the IR bands) and the subsequent exchange table are consistent with the observed Eu and A2u lines and give a magnon dispersion that can be checked later by neutrons.\n\nThe soft spot is exactly the one the reader flags: D ≈ 0.1–0.2 meV comes from a mean-field J1 ≈ 4 meV extracted from TN ≈ 350 K under the assumption that J1 dominates and S = 2, then plugged into the linear-spin-wave formula. The paper itself calls this an order-of-magnitude estimate, cross-checks it against the DFT J’s (which give D ≈ 0.1 meV), and does not rest the mode identification or the room-temperature claim on the precise value. The 3/4 temperature rescaling of the mean-field curves is post-hoc and cosmetic. None of that undermines the central spectroscopic result.\n\nThis is useful catalogue material for anyone working on ambient-temperature AF spintronics or THz magnonics, and for people who care about exfoliable Mn-based AFs. The math and data look solid; the citation pattern is appropriate. I would send it to referees without hesitation and would cite the AFMR energy and the easy-axis confirmation myself.","headline":"Clean first AFMR data on a room-temperature easy-axis AF semiconductor; the spectroscopy is solid and the anisotropy estimate is correctly labeled as rough.","tokens_in":14313,"tokens_out":551,"would_cite":true,"duration_ms":4905,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.5","headline":"Bulk NaMnAs shows a clear 7 meV antiferromagnetic resonance that remains visible at room temperature, confirming easy-axis order along the tetragonal axis.","keywords":["antiferromagnetic resonance","NaMnAs","easy-axis antiferromagnet","THz magnon","single-ion anisotropy","room-temperature antiferromagnetism","layered magnetic semiconductor"],"falsifier":"Inelastic neutron scattering that maps the full magnon dispersion at low temperature would either confirm or contradict the predicted gap and the relative strengths of the exchange paths used to extract D.","tokens_in":14303,"feed_emoji":"🧲","tokens_out":697,"duration_ms":7316,"temperature":0.7,"pith_summary":"NaMnAs is a layered antiferromagnetic semiconductor that orders well above room temperature. This work uses THz magneto-transmission to detect its zero-wavevector magnon. At zero field the resonance sits at 7 meV; with field along the tetragonal axis it splits linearly into two branches, the classic signature of an easy-axis antiferromagnet. The mode softens with temperature but is still clearly present at 295 K. From the measured gap and the known Néel temperature the authors extract a single-ion anisotropy of roughly 0.1–0.2 meV for the manganese ions—larger than typical values in other Mn-based antiferromagnets. The result supplies a concrete, ambient-temperature THz magnetic excitation in an exfoliable crystal and thereby opens a practical materials platform for room-temperature antiferromagnetic spintronics and magnonics.","feed_headline":"NaMnAs shows a 7 meV magnon still visible at room temperature","feed_subtitle":"Easy-axis AFMR confirms Néel order above 295 K and yields a sizable Mn anisotropy of 0.1–0.2 meV","key_machinery":"Kittel’s semiclassical AFMR formulae for easy-axis antiferromagnets: the zero-field gap splits linearly as ω0 ± g µB B∥ when the field is along the easy axis and follows a square-root form when the field is perpendicular; these expressions, together with the linear-spin-wave gap formula relating the gap to single-ion anisotropy D and exchange, convert the measured resonance into a quantitative anisotropy estimate.","core_discovery":"At B = 0 a single antiferromagnetic-resonance line is observed at 7.0 ± 0.2 meV and is identified as the doubly degenerate k = 0 magnon of an easy-axis antiferromagnet whose Néel vector lies along the tetragonal axis. The mode remains clearly visible up to 295 K while softening to 5.4 meV, and the extracted single-ion anisotropy of the Mn ions is 0.1–0.2 meV.","pith_inferences":[],"forward_implications":[],"fun_headline_variants":["NaMnAs AFMR shows 7 meV magnon still clear at 295 K","Easy-axis NaMnAs: 7 meV k=0 magnon softens but lasts to room temp","7 meV doubly-degenerate magnon in NaMnAs persists to 295 K","Room-temp AFMR pins Mn anisotropy at 0.1–0.2 meV in NaMnAs","NaMnAs Néel vector along c confirmed by 7 meV AFMR to 295 K"],"cache_read_input_tokens":128,"weakest_assumption_plain":"The quoted anisotropy of about 0.2 meV rests on a mean-field estimate of the dominant exchange constant taken from the Néel temperature under the assumption that only one exchange path matters and that the spin is S = 2; both steps are order-of-magnitude approximations.","fun_headline_variants_meta":{"raw":{"variants":["NaMnAs AFMR shows 7 meV magnon still clear at 295 K","Easy-axis NaMnAs: 7 meV k=0 magnon softens but lasts to room temp","7 meV doubly-degenerate magnon in NaMnAs persists to 295 K","Room-temp AFMR pins Mn anisotropy at 0.1–0.2 meV in NaMnAs","NaMnAs Néel vector along c confirmed by 7 meV AFMR to 295 K"]},"model":"grok-4.5","effort":"low","cost_usd":0.0039,"raw_usage":{"total_tokens":1204,"prompt_tokens":735,"num_sources_used":0,"completion_tokens":129,"cost_in_usd_ticks":39000000,"prompt_tokens_details":{"text_tokens":735,"audio_tokens":0,"image_tokens":0,"cached_tokens":256},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":340,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":735,"tokens_out":129,"duration_ms":4780,"temperature":1.0,"reasoning_tokens":340,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-07-13T17:55:40.641936+00:00","model_set":{"reader":"grok-4.5"},"falsifier":"Inelastic neutron scattering that maps the full magnon dispersion at low temperature would either confirm or contradict the predicted gap and the relative strengths of the exchange paths used to extract D.","supporting_citations":[],"review_version":1}