{"id":"2bd87558-09f1-4d2b-a4db-bf97d07aea5d","arxiv_id":"2506.05926","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":4,"one_line_summary":"Time-dependent Hall voltage measurements in Mn5Si3 Hall bars reveal magnetic-viscosity-like relaxation and step-like jumps attributed to Barkhausen reorientations of altermagnetic Hall vector domains.","lead":"Hall voltage measurements on thin films of the altermagnet candidate Mn5Si3 show slow logarithmic relaxation and abrupt step-like jumps at fixed magnetic field, which the authors interpret as magnetic viscosity and Barkhausen domain reorientations. The work extends domain-dynamics phenomena, previously known in ferromagnets, to altermagnetic materials.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The Barkhausen attribution is the load-bearing claim, but the paper provides no control to rule out non-magnetic step sources such as magnet field drift, contact instabilities, or charge-trapping; a step in V_AHE(t) is not yet shown to be magnetic.","rationale":"The reader's weakest assumption identifies the same load-bearing concern: the abrupt Hall voltage steps have not been shown to be magnetic rather than instrumental or electronic in origin. My reading of the full text strengthens this concern by noting a specific, quantifiable mechanism that the manuscript does not exclude: the ordinary Hall term is subtracted using a fixed field value, so magnet flux creep or a discrete field jump on the order of 0.04 mT would produce exactly the size of voltage step the analysis is built to detect. The absence of a control above the ordering temperature, on a nonmagnetic reference device, or with field monitoring is therefore not a minor omission but a direct threat to the central claim. The aftereffect portion of the paper is better supported: the log-time fits have high R² values and the extracted viscosities are comparable to ferromagnetic films, so the relaxation observation is plausible on its own. However, the 18 nm Barkhausen length is derived from the step amplitudes via Eq. (5), and if the steps are not magnetic, that derivation is meaningless. Since the reader's verdict is already conditional and explicitly requests magnetic-origin evidence, my stress-test does not move the verdict; it sharpens the specific control that would settle the issue. If the proposed high-temperature or reference-device run shows no steps, the Barkhausen claim gains real support. If steps persist in the non-magnetic regime, the central claim should be rejected or substantially revised.","tokens_in":9759,"tokens_out":7204,"duration_ms":80807,"concrete_test":"Run the identical 30-minute V_Δ-(t) protocol on the same 100-nm Hall bar at a temperature above the magnetic ordering transition (e.g., 300 K), using the same magnet sweep, current density, and the same rolling-median, fit-subtraction, differentiation, rolling-sum, and 3σ analysis pipeline. Count the number and amplitudes of identified steps. If unilateral steps above the ~100 nV sensitivity limit persist, the Barkhausen interpretation and the derived L_Bark value are not supported; if no such steps are detected, the magnetic-origin attribution is substantially strengthened.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central new claim is that the unilateral voltage steps in the Hall time traces are Barkhausen jumps of altermagnetic Hall-vector domains, and that their amplitudes imply a Barkhausen length of about 18 nm. This is the step that would make the paper significant. It would be secure only if all non-magnetic contributions to V_AHE(t) were absent or independently measured, and that is not demonstrated. In particular, the analysis uses V_AHE(t) = V_Δ-(t) - a·H_meas - b. The ordinary Hall coefficient a is subtracted with a constant field value, so any slow drift or discrete flux jump of the superconducting magnet translates directly into a voltage step of amplitude a·ΔH. For the 100-nm device, |a| ≈ 2.6 µV/T, so a step of roughly 100 nV, the stated sensitivity limit, corresponds to a field excursion of only about 0.04 mT. The paper reports no simultaneous field monitoring, no measurement above the magnetic ordering transition, no nonmagnetic reference device, and no reversal-symmetry check such as saturating at the opposite field and verifying that the step polarity reverses. The rolling-median, fit-subtraction, differentiation, rolling-sum, and 3σ-threshold pipeline would flag any step-like event of adequate amplitude, including contact or charge-trapping events. The smooth log-time relaxation fits support the magnetic aftereffect, but they do not validate the step attribution. Thus the Barkhausen interpretation and the derived 18 nm length rest on an unverified rejection of non-magnetic step sources.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript reports time-dependent Hall voltage measurements on Mn5Si3 thin-film Hall bars with widths from 10 µm to 0.1 µm at 130 K. For the 10 µm bar, the anomalous Hall relaxation after field steps is fitted with a logarithmic law, yielding a magnetic viscosity S_n up to 6.4% and time constants of tens of seconds, comparable with ferromagnetic films. For narrower bars, the time traces contain abrupt unilateral voltage steps which the authors interpret as Barkhausen steps of altermagnetic Hall-vector domains. From the step amplitudes via Eq. (5) they estimate a Barkhausen length L_Bark of about 18 nm in the 100 nm wide device, with larger values for wider bars attributed to a detection sensitivity limit.","tokens_in":10176,"tokens_out":4349,"duration_ms":42467,"significance":"The magnetic aftereffect observation is a solid, quantitative addition to the phenomenology of altermagnetic candidates and is well supported by high-R^2 fits for the 10 µm device. If the Barkhausen interpretation survives additional controls, the paper would provide the first report of domain-like dynamics in an altermagnet and a rare length-scale estimate for Hall-vector textures. However, the central claim currently rests on the assumption that every detected step is magnetic in origin, and the manuscript does not yet rule out instrumental sources of step-like voltages. The 18 nm value is model-dependent and an upper bound rather than a directly measured domain size. Credit is due for the careful fitting procedure and for the explicit acknowledgment of the surprising width dependence of L_Bark, which the authors attempt to rationalize through a sensitivity limit.","major_comments":[{"comment":"The step detection pipeline selects all local maxima above 3σ in the differentiated residual, but no control experiment is presented to distinguish magnetic Barkhausen steps from non-magnetic voltage steps. The subtraction V_AHE(t) = V_Δ−(t) − a·μ0H_meas − b uses the nominal field H_meas; any drift or discrete flux jump of the superconducting magnet of amplitude ΔH enters as a·ΔH. For the w = 0.1 µm device, |a| = 2.6 µV/T (Table 1), so a step at the stated 100 nV detection limit corresponds to only about 0.04 mT. Without simultaneous field monitoring, measurements above the magnetic ordering temperature, a nonmagnetic reference device, or a reversal-symmetry check, the unilateral steps cannot be assigned to magnetic domain reorientation. This directly undermines the Barkhausen effect claim and the derived 18 nm length.","section":"Fig. 3 and the paragraph beginning 'For a quantitative evaluation of L_Bark'"},{"comment":"The conversion ΔV_Bark/ΔV_AHE = Y_Bark/Y_active assumes a volume-fraction linearity and a square Barkhausen volume spanning the full film thickness. The manuscript does not report the number of steps used for each average, the spread of individual L_Bark values, or error bars on the fit parameters in Eq. (2). The grey sensitivity line in Fig. 3c is based on an assumed 100 nV noise floor without a measured noise distribution. Consequently the headline value L_Bark = 18 nm is an upper bound under a specific geometrical and electrical model rather than a measured domain size. The authors should provide per-step statistics, detection thresholds, and a propagation of uncertainties.","section":"Eq. (5), Fig. 3c"},{"comment":"The Barkhausen step extraction for w ≤ 1 µm relies on subtracting a fit to Eq. (2) from data for which the same fit has R^2 as low as 0.5. The manuscript does not demonstrate that the residual-based detection is robust to this poor baseline model. A sensitivity analysis with a different baseline (e.g., a local median without the logarithmic fit) or a quantification of the fit residual's influence on the detected step amplitudes is needed to support the step amplitudes extracted from the narrower devices.","section":"Fig. 2 and the sentence beginning 'While our Mn5Si3 Hall bar devices with w < 10 µm'"}],"minor_comments":[{"comment":"The phrase 'micropatterned into M5Si3 films' should read 'Mn5Si3 films'.","section":"Introduction, 'M5Si3'"},{"comment":"The value j_x = 2.5 × 10^{−10} A/m^2 appears to be a typo; current densities of order 10^{10} A/m^2 are typical for such experiments.","section":"Experimental methods"},{"comment":"The average L_Bark values are placed inside the data panel; labeling outside the panel or in the caption would improve readability.","section":"Fig. 3c"},{"comment":"The sentence 'The time interval associated with the rolling sum and rolling median were chosen to be of the same size' has a subject-verb agreement error and should be revised.","section":"Barkhausen detection paragraph"}],"recommendation":"major_revision","confidential_remarks":"The paper is within scope for a condensed matter experimental journal, and the aftereffect part is solid. The Barkhausen claim is plausible but requires the controls described in the major comments; I would not reject because the missing checks are experimentally feasible and the authors have the relevant expertise. I encourage the editor to require the additional control measurements and a more cautious presentation of the 18 nm value as a model-dependent upper bound."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Gist: the aftereffect half of this paper is solid; the Barkhausen half is a plausible interpretation that the paper doesn't yet make load-bearing.\n\nThe genuinely new thing is the first time-dependent Hall relaxation and step-like features in an altermagnet candidate, and the aftereffect measurement is well done. The logarithmic fits to the 10 µm bar are clean—R^2 above 0.98—and the extracted S_n and t0 sit in the same range as PMA ferromagnet films. That part earns its place.\n\nThe soft spot is exactly where the reader put it: the Barkhausen attribution. The unilateral steps are flagged by a rolling-median/fit-subtraction/differentiation/threshold pipeline that will catch any step of adequate amplitude, and there is no control that the steps are magnetic. No measurement above T_N, no nonmagnetic reference device, no simultaneous field monitoring, no polarity-reversal check. Given that the OHE coefficient is subtracted with a constant field value, a small field drift or flux jump of the superconducting magnet would produce a voltage step of the right size: for the 100 nm device, |a| ≈ 2.6 µV/T, so a 100 nV step is a 0.04 mT field jump. That's not a straw objection.\n\nThe 18 nm number comes from Eq. (5), which assumes a square domain spanning the film thickness, and the strong width dependence is reconciled by a sensitivity-limit argument that is internally consistent but post hoc. The authors are candid about the surprise—they flag the width dependence themselves—which helps, but candor is not evidence. The absence of error bars on step statistics is a minor issue by comparison.\n\nI don't think this is a flawed paper or a misleading one. The aftereffect is real, and the Barkhausen reading is reasonable. It just needs one decisive control. A referee should push for a temperature sweep above the ordering transition, or a reference device, or a demonstration that the step polarity reverses when the saturation direction is reversed. That would settle it.\n\nThis paper is for the altermagnet and transport subfield, and it should get refereed. The claim is central enough that the referee time is justified even if the final outcome is heavy revision.","headline":"The aftereffect measurement is solid; the Barkhausen attribution is plausible but unproven until a non-magnetic control is shown.","tokens_in":10635,"tokens_out":2609,"would_cite":true,"duration_ms":26753,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"Hall-voltage steps point to magnetic domains in an altermagnet.","keywords":["altermagnetism","anomalous Hall effect","Mn5Si3","Barkhausen effect","magnetic aftereffect","magnetic viscosity","magnetic domains","Hall bar"],"falsifier":"Run the identical relaxation protocol, 30 minutes at fixed field after saturation, on a Mn5Si3 film heated above its magnetic ordering temperature or on an identically patterned nonmagnetic metal film; if step-like jumps and logarithmic relaxation persist there, the Barkhausen and aftereffect interpretation collapses. A confirming observation would be direct real-space imaging of Hall-vector domains of the order of 10 to 20 nm in the same films.","tokens_in":1862,"feed_emoji":"🧲","tokens_out":6201,"duration_ms":141953,"temperature":0.7,"pith_summary":"This paper reports time-dependent Hall-effect measurements on micron-scale Hall bars patterned from thin films of Mn5Si3, a candidate altermagnet. At a fixed magnetic field, the anomalous Hall voltage relaxes over tens of minutes in a way that matches the magnetic-viscosity response of ferromagnetic films. Superimposed on that relaxation, the voltage traces show abrupt, unilateral steps that the authors interpret as Barkhausen steps, i.e., sudden reorientations of magnetic Hall-vector domains. If the interpretation holds, it establishes that altermagnets, like ferromagnets, exhibit magnetic aftereffect and Barkhausen-type domain dynamics, and it places an upper bound of about 18 nm on the size of the reversing domain in the narrowest devices.","feed_headline":"Altermagnet Mn5Si3 shows Barkhausen steps in Hall voltage","feed_subtitle":"Time-resolved Hall data suggest altermagnets relax like ferromagnets, with domain flips as small as 18 nm.","key_machinery":"The load-bearing object is the altermagnetic Hall vector $h_{Hall}$, which plays the role that magnetization plays in ferromagnets within the anomalous Hall response $V_{xy} = j_x w \\mu_0 (R_O H_0 + R_A h_{Hall})$; it is what the Hall voltage measures and what supposedly reorients in the observed steps. The conversion of a measured voltage step into a physical domain size runs through the identity $Y_{Bark}/Y_{active} = \\Delta V_{Bark}/\\Delta V_{AHE} = L_{Bark}^2/w^2$, which assumes a square Barkhausen volume spanning the full 19.3 nm film thickness. The step-detection pipeline, consisting of a rolling median of 30 points, subtraction of a $\\ln(1+t/t_0)$ relaxation fit, numerical differentiation, a rolling sum, and a three-$\\sigma$ threshold on local maxima, is the mechanism by which the paper turns noisy relaxation traces into discrete Barkhausen events.","core_discovery":"The central claim is that the altermagnetic candidate Mn5Si3 exhibits both the magnetic aftereffect and the Barkhausen effect, two hallmarks of domain-mediated magnetization dynamics previously studied mainly in ferromagnets. Recording the anomalous Hall voltage $V_{AHE}(t)$ at fixed field after saturating the sample, the authors find a logarithmic relaxation quantitatively similar to ferromagnets with perpendicular anisotropy (normalized viscosity $S_n$ up to 6.4%, time constants of tens of seconds). On top of this relaxation, the time traces contain step-like jumps, which the authors attribute to abrupt reorientations of the altermagnetic Hall vector $h_{Hall}$ in a portion of the sample volume. From the step amplitudes and the relation $Y_{Bark}/Y_{active} = \\Delta V_{Bark}/\\Delta V_{AHE} = L_{Bark}^2/w^2$, they extract a Barkhausen length $L_{Bark} \\approx 18\\,\\mathrm{nm}$ in 100 nm wide Hall bars, which they interpret as an upper bound on the size of Hall-vector domains. They further argue that the observation of multiple Barkhausen steps in devices known to contain only a single altermagnetic variant implies that more than one type of magnetic texture must be considered in altermagnetic thin films.","pith_inferences":["The paper does not report control measurements above the magnetic ordering temperature or on nonmagnetic reference devices; a natural extension is to run the identical 30-minute protocol on such controls and check that no step-like jumps appear.","If the 18 nm scale is confirmed, the elementary switching volume in Mn5Si3 is far smaller than device dimensions, which would matter for any memory or logic application that relies on deterministic reversal of altermagnetic domains.","The unilateral character of the steps and their distribution in time carry information about domain-wall pinning statistics; analyzing waiting times versus field could connect the discrete jumps to the same thermally activated barrier landscape that produces the logarithmic aftereffect.","Measuring the same films in unpatterned form with a spatially resolving probe could separate intrinsic Hall-vector domain size from patterning-induced effects, testing the paper's width-dependence explanation."],"forward_implications":["The magnetic aftereffect in Mn5Si3 is quantitatively comparable to ferromagnetic films with perpendicular anisotropy, with normalized viscosity up to 6.4%, so altermagnetic relaxation can be studied with the same Hall-probe toolbox used for ferromagnets.","Barkhausen steps in 100 nm wide Hall bars bound the reversing volume by a Barkhausen length of about 18 nm, a scale consistent with the strain-relief structural domains reported in Mn5Si3 growth studies.","The Barkhausen length grows with Hall bar width, from 18 nm at 0.1 µm to 455 nm at 10 µm, which the authors attribute to micropatterning altering the magnetic texture, an effect that must be accounted for when patterning altermagnetic devices.","Observing multiple Barkhausen steps in devices that host a single altermagnetic variant implies that several distinct Hall-vector textures coexist, so altermagnetic domain discussions should not be restricted to the known variants.","The narrowest devices offer the best sensitivity to Barkhausen events because the voltage-step resolution limit of about 100 nV scales favorably with width."],"supporting_citations":[{"why":"Defines altermagnetism as a distinct collinear magnetic order and establishes that it supports the anomalous Hall effect; supplies the concept the paper extends.","marker":"[1]"},{"why":"Establishes the altermagnetic Hall vector in Mn5Si3 and the anomalous Hall response used as the measurement probe.","marker":"[12]"},{"why":"The original Barkhausen effect reference; the phenomenon whose observation in Mn5Si3 is the paper's headline claim.","marker":"[19]"},{"why":"Provides the Barkhausen-effect model linking abrupt magnetization changes to voltage steps, the interpretive basis for the step attribution.","marker":"[20]"},{"why":"Supplies the magnetic-viscosity analysis method and the ferromagnetic comparison values used to benchmark Mn5Si3 relaxation.","marker":"[21]"},{"why":"Provides the logarithmic relaxation form used to fit the aftereffect data.","marker":"[22]"},{"why":"Reports the growth of Mn5Si3 films and the strain-stabilized altermagnetic phase; the material basis of the experiment.","marker":"[23]"},{"why":"Documents the patterning of Mn5Si3 into Hall bars and the identification of a single altermagnetic variant in 100 nm devices, the comparison that motivates the multi-texture conclusion.","marker":"[24]"},{"why":"Reports the anomalous Hall hysteresis and topological-Hall shoulder in Mn5Si3, the loop features that the relaxation and step analysis build on.","marker":"[25]"}],"fun_headline_variants":["Barkhausen steps in altermagnet Mn5Si3 films","Altermagnet Mn5Si3 mimics ferromagnet relaxation","18-nm domain flips seen in altermagnet candidate","Mn5Si3 shows magnetic aftereffect and Barkhausen jumps","Altermagnet Hall data reveal Barkhausen-like steps"],"cache_read_input_tokens":12672,"weakest_assumption_plain":"The abrupt steps in the Hall voltage are assumed to be magnetic domain reorientations rather than electrical noise, contact instabilities, charge trapping, or other artifacts; the paper's detection pipeline selects every local maximum above three standard deviations, and no control measurements on nonmagnetic samples or above the magnetic ordering temperature are presented.","fun_headline_variants_meta":{"raw":{"variants":["Barkhausen steps in altermagnet Mn5Si3 films","Altermagnet Mn5Si3 mimics ferromagnet relaxation","18-nm domain flips seen in altermagnet candidate","Mn5Si3 shows magnetic aftereffect and Barkhausen jumps","Altermagnet Hall data reveal Barkhausen-like steps"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000178,"raw_usage":{"total_tokens":1307,"prompt_tokens":964,"completion_tokens":343,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":580,"completion_tokens_details":{"reasoning_tokens":258}},"tokens_in":580,"tokens_out":343,"duration_ms":3621,"temperature":1.0,"reasoning_tokens":258,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-07T10:12:47.134751+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Run the identical relaxation protocol, 30 minutes at fixed field after saturation, on a Mn5Si3 film heated above its magnetic ordering temperature or on an identically patterned nonmagnetic metal film; if step-like jumps and logarithmic relaxation persist there, the Barkhausen and aftereffect interpretation collapses. A confirming observation would be direct real-space imaging of Hall-vector domains of the order of 10 to 20 nm in the same films.","supporting_citations":[{"cited_title":"Šmejkal, J","cited_arxiv_id":null,"evidence_quote":"Defines altermagnetism as a distinct collinear magnetic order and establishes that it supports the anomalous Hall effect; supplies the concept the paper extends."},{"cited_title":"Leiviskä, J","cited_arxiv_id":null,"evidence_quote":"Establishes the altermagnetic Hall vector in Mn5Si3 and the anomalous Hall response used as the measurement probe."},{"cited_title":"Barkhausen","cited_arxiv_id":null,"evidence_quote":"The original Barkhausen effect reference; the phenomenon whose observation in Mn5Si3 is the paper's headline claim."},{"cited_title":"Alessandro, C","cited_arxiv_id":null,"evidence_quote":"Provides the Barkhausen-effect model linking abrupt magnetization changes to voltage steps, the interpretive basis for the step attribution."},{"cited_title":"Beckert, R","cited_arxiv_id":null,"evidence_quote":"Supplies the magnetic-viscosity analysis method and the ferromagnetic comparison values used to benchmark Mn5Si3 relaxation."},{"cited_title":"Xi, K.-Z","cited_arxiv_id":null,"evidence_quote":"Provides the logarithmic relaxation form used to fit the aftereffect data."},{"cited_title":"Kounta, H","cited_arxiv_id":null,"evidence_quote":"Reports the growth of Mn5Si3 films and the strain-stabilized altermagnetic phase; the material basis of the experiment."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Documents the patterning of Mn5Si3 into Hall bars and the identification of a single altermagnetic variant in 100 nm devices, the comparison that motivates the multi-texture conclusion."},{"cited_title":"Reichlova, R","cited_arxiv_id":null,"evidence_quote":"Reports the anomalous Hall hysteresis and topological-Hall shoulder in Mn5Si3, the loop features that the relaxation and step analysis build on."}],"review_version":1}