{"id":"a672e53f-0e4c-4334-8593-a0e3e5536e7c","arxiv_id":"2608.10310","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":4,"one_line_summary":"Scanning NV magnetometry images the static and microwave stray fields of vortex wall and azimuthal modes in permalloy at about 50 nm resolution, with a 40x microwave enhancement near the core.","lead":"This paper shows that a scanning nitrogen-vacancy magnetometer can image both the static magnetic fields and the microwave fields of magnetic vortices in small permalloy structures with roughly 50 nanometer resolution. A generalist reader might care because it offers a tabletop, high-resolution way to characterize magnonic and quantum-hybrid devices that today usually requires synchrotron X-ray beamlines.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The disc vortex-mode identification and the disorder-dependent decay results rely on a tuned, unmeasured 1-µm grain disorder model; this is the load-bearing assumption for the quantitative disc claims.","rationale":"The reader's weakest assumption identifies exactly the load-bearing point: the disc vortex-mode identification and disorder-dependent decay conclusions rest on an unmeasured, tuned disorder model. The manuscript's own statements support this reading: the disc static field alone cannot identify a vortex, and the square height-decay maps are acknowledged to contain large errors. The square feature provides an independent demonstration of the SNVM technique, so the central imaging capability claim remains credible. However, the headline quantitative results attributed to the vortex azimuthal mode in the disc are conditional on the simulated disorder model matching the real microstructure. The proposed microstructure measurement and disorder-parameter sweep would settle whether the mode assignment and decay maps are robust or artifacts of the chosen model. Since the reader already assigned CONDITIONAL with moderate confidence, no verdict change is needed.","tokens_in":16665,"tokens_out":8279,"duration_ms":98965,"concrete_test":"Measure the actual grain structure of the same permalloy film by TEM or EBSD, build a micromagnetic model with the measured grain map, and recompute the 2.85 GHz stray-field maps and height-dependent decay constants. Then repeat with disorder parameters varied over a realistic range (0.1–2 µm grains, 1–10% M_s and anisotropy variation, 0–10% exchange reduction) and check whether the vortex-mode assignment, the 40x enhancement point, and the decay-constant map remain within the experimental uncertainties. If they do not, the disc-specific quantitative claims need to be re-qualified.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim that the disc's microwave maps image the vortex azimuthal mode and reveal disorder-dependent evanescent decay depends on micromagnetic simulations whose disorder model (1 µm Voronoi grains, ±5% M_s and anisotropy variations, 5% exchange reduction at boundaries) was chosen to reproduce the data, not measured on the actual film. The authors themselves state that no vortex can be definitively identified from the disc's static stray-field map; the core location and mode assignment come from matching the simulated dynamic map. Control simulations of alternative textures show different magnitudes, which is useful, but they are run for only one disorder parameter set. If the actual grain structure or disorder strength differs from the tuned model, the extracted core position, the 40x enhancement, and the decay-constant maps could all shift. This matters because the abstract and discussion elevate exactly these quantitative results. The square measurements provide independent support for the technique, so the core imaging claim is not overturned, but the disc-specific quantitative claims are conditional. A relevant self-reported limitation is the supplementary note that the height-dependent square decay maps contain large errors because the fly height is comparable to the decay constant; this reinforces that decay measurements near the resolution limit need validation.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript reports scanning nitrogen-vacancy (NV) magnetometry imaging of static and microwave-frequency magnetic fields emanating from permalloy microstructures hosting magnetic vortices: a 1 µm square and a 6 µm diameter disc. Using ODMR, the authors image static stray fields; using the ODMR linewidth (FWHM) and Rabi oscillation frequencies, they map microwave field amplitudes with ~50 nm resolution. They report a 40× enhancement of the microwave field near the vortex core in the disc, spatially varying evanescent decay constants (k = 17.20 µm⁻¹ and 12.56 µm⁻¹ for the square's wall modes; k = 3.09 µm⁻¹ for the disc's azimuthal mode), and qualitative agreement with micromagnetic simulations that include a disorder model based on 1 µm Voronoi grains with ±5% variations in saturation magnetization and anisotropy and a 5% exchange reduction at grain boundaries.","tokens_in":16825,"tokens_out":5629,"duration_ms":53565,"significance":"If the results hold, this work establishes SNVM as an accessible tabletop technique for nanoscale imaging of vortex magnon modes, with resolution demonstrably better than diffraction-limited optical methods and with quantitative field mapping via Rabi measurements. The paper includes valuable internal consistency checks (FWHM versus Rabi correlation), calibration details, and control simulations of alternative magnetization textures that do not reproduce the data. However, the quantitative disc-specific claims (40× enhancement, decay constants, core localization) rely on a disorder model whose parameters were chosen to reproduce the measurements rather than independently measured, and some decay measurements are taken near the resolution limit of the technique. These caveats do not overturn the core imaging demonstration, but they currently limit the strength of the quantitative conclusions.","major_comments":[{"comment":"The assignment of the disc's microwave maps to the azimuthal vortex mode and the localization of the vortex core are not established by the static stray-field data alone, as the authors acknowledge in the text; they are inferred from agreement with micromagnetic simulations that include a disorder model (1 µm Voronoi grains, ±5% variations in M_s and anisotropy, 5% exchange reduction at grain boundaries) whose parameters were chosen to match the experiment. This creates a circularity for the quantitative disc claims: the 40× enhancement in Fig. 4(E), the decay constant k = 3.09 µm⁻¹ in Fig. 5(D), and the spatially varying decay maps in Fig. 5(A) all depend on this core/mode assignment. The authors should either characterize the actual microstructure (e.g., by transmission electron microscopy or magnetic force microscopy) or perform a sensitivity study over a plausible range of disorder parameters and grain sizes, showing that the core location, enhancement factor, and decay-length ranges are robust. Without such validation, the disc-specific quantitative results remain model-dependent.","section":"Results, disc measurements (Figs. 3–5)"},{"comment":"The square's decay constants (k = 17.20 µm⁻¹, decay length 58 nm; k = 12.56 µm⁻¹, decay length 80 nm) are quoted from single-point Rabi height scans, yet the supplementary text states that the height-dependent ODMR maps for the square 'contained large errors because of the very rapid measured decays and our tip's fly height, which was comparable to the decay constant.' Since the decay lengths are comparable to or smaller than the NV-sample separation used in the measurements, the single-point fits may not reliably constrain k; the paper should show the height-series data with the fitted exponentials, report confidence intervals, and discuss how the limited height range (relative to the decay length) affects the extracted values. This is important because the contrast between the square and disc decay lengths is used to motivate the qubit-transduction discussion.","section":"Supplementary Materials, 'Additional ODMR data - height dependence' and Fig. 2(F)"},{"comment":"The 40× enhancement is presented as a key quantitative result, but it is obtained from a single Rabi measurement at a point identified as 'near the vortex core' based on the simulated dynamic map rather than on the measured static stray field. Given the ~56 nm imaging resolution and the uncertainty in the core position (which the authors state cannot be definitively identified from the static map), the paper should provide an uncertainty estimate for this enhancement factor and, ideally, a map of the enhancement across the core region to demonstrate that the quoted value is representative rather than a fortuitous local maximum.","section":"Results, Fig. 4(E) and Discussion"}],"minor_comments":[{"comment":"The text refers to a '40× increase in MW power' in Fig. 4(E), but the measured quantity is the Rabi frequency, which is proportional to the microwave magnetic field amplitude, not the power. Please make the units consistent (e.g., amplitude or Rabi frequency).","section":"Abstract and Fig. 4(E)"},{"comment":"The polarization analysis in the supplementary shows that microwave power variations between the two ODMR transitions can produce false polarization signals of up to ~12°. Since polarization analysis is presented as a potential advantage in the main text, a brief note in the main text about this caveat would be appropriate.","section":"Supplementary Materials, Fig. S8"},{"comment":"The phrase 'the sample topopgraphy' contains a typo; it should read 'topography.'","section":"Materials and Methods"},{"comment":"The text says the central vortex core 'spanned only one pixel' and was filtered out during image processing; it would help to state whether the filtering could affect the apparent core size in the displayed field maps.","section":"Figure 1 caption"},{"comment":"The term 'disc' is used for what appears to be the square feature in the Fig. S4 caption; please unify the terminology to avoid confusion.","section":"Supplementary Materials, Fig. S4 caption"}],"recommendation":"major_revision","confidential_remarks":"The paper is a strong demonstration of a technique, and the square measurements plus the internal consistency checks provide a solid basis for the central imaging claim. The main concern is the dependence of the disc-specific quantitative results on a tuned disorder model; this is fixable with a sensitivity analysis or independent microstructure characterization. I would be willing to review a revised version. The paper is within the scope of the journal and likely to have significant impact if the quantitative claims are made robust."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Colleague,\n\nQuick take: this is a genuine step forward. The authors demonstrate scanning NV magnetometry of both static and microwave stray fields from vortex magnon modes at ~50 nm resolution, combining two capabilities that previously lived in separate papers (fixed-NV vortex dynamics, scanning-NV static vortex imaging). The square-feature results are the strongest part: the vortex is positively identified from the static stray field, the wall-mode dynamics match simulations, and the Rabi-frequency/FWHM correlation provides an internal consistency check. I believe the central claim—that this technique can image vortex dynamics at nanoscale resolution—holds up.\n\nThe soft spots are concentrated in the disc measurements. The vortex cannot be identified from the static stray-field map alone, and the azimuthal-mode assignment plus the extracted core location rest on matching simulations that use a 1-µm Voronoi grain disorder model with ±5% magnetization/anisotropy variation and 5% exchange reduction. Those parameters were chosen to reproduce the data, not measured on the actual film. So the headline 40× enhancement and the decay constants (3.09, 12.56, 17.20 µm⁻¹) should be treated as conditional, and none carry error bars. The control simulations of saturated and domain-wall textures are useful, but they use a single disorder parameter set. The supplementary also admits the square's height-dependent decay maps carry large errors because the fly height is comparable to the decay constant—so the decay measurements near the resolution limit need independent validation.\n\nWhat the paper does well beyond the central demo is honest self-assessment. The polarization analysis is carefully checked against spin-mixing and frequency-dependent power variations, and the authors concede that over a fifth of the measured polarization could be an artifact. That level of scrutiny is credible. The citation pattern also looks fair: prior fixed-NV vortex studies and scanning static imaging are both properly acknowledged.\n\nWho is this for? Anyone interested in magnonic device characterization or NV-based microwave imaging. It offers a tabletop route to nanoscale resolution without a synchrotron. The paper deserves a serious referee, not a desk reject. I would send it to peer review with a request to strengthen the disc section—ideally a sensitivity analysis of the disorder model and explicit error bars on the quoted numbers. The core imaging claim stands; the disc-specific quantitative claims are conditional, but addressable.","headline":"A real technical advance—scanning NV imaging of vortex magnon modes at ~50 nm resolution—with the disc-specific quantitative results resting on a tuned disorder model that needs scrutiny.","tokens_in":17441,"tokens_out":2507,"would_cite":true,"duration_ms":27051,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"Scanning NV magnetometry images both static and microwave magnetic fields of ferromagnetic vortices at roughly 50 nm resolution, revealing disorder-dependent evanescent decay and a 40-fold field enhancement near a vortex core.","keywords":["scanning NV magnetometry","ferromagnetic vortex","magnonics","spin waves","microwave field imaging","Rabi oscillation","micromagnetic simulation","permalloy"],"falsifier":"Measure the actual grain structure of the same 6 µm permalloy disc, for example with electron backscatter diffraction or transmission electron microscopy, and rerun the 2.85 GHz micromagnetic simulations using those measured grain sizes, orientations, and boundary exchange parameters instead of the assumed 1 µm Voronoi grains. If the simulated azimuthal-mode microwave maps and decay-length maps no longer reproduce the measured ODMR and Rabi images, the vortex-mode assignment and the disorder-dependent decay conclusions would be refuted.","tokens_in":16396,"feed_emoji":"🧲","tokens_out":12135,"duration_ms":103891,"temperature":0.7,"pith_summary":"Scanning nitrogen-vacancy (NV) magnetometry is normally used for static magnetic textures; this paper extends it to the GHz microwave fields emitted by ferromagnetic vortex modes. With a diamond tip containing a single NV center, the authors image the static stray field and the microwave response of vortex states in a 1 µm permalloy square and a 6 µm permalloy disc at roughly 50 nm resolution. The microwave maps match micromagnetic simulations and show one mode radiating along the square's magnetic domain walls and an azimuthal vortex mode concentrated near the disc's core. Near the core, the vortex amplifies the applied microwave field by a factor of 40, and the evanescent decay of these microwaves varies with position and with film disorder. If correct, this makes SNVM a tabletop, substrate-agnostic way to characterize magnonic and qubit-hybrid devices at resolutions diffraction-limited optics cannot reach.","feed_headline":"Vortex microwaves imaged at 50 nm by a tabletop diamond-tip magnetometer","feed_subtitle":"A single NV center maps vortex spin-wave fields, exposing disorder effects and a 40-fold field boost.","key_machinery":"The working mechanism is a rastered diamond tip whose single nitrogen-vacancy (NV) center acts as a local magnetic-field sensor. In the power-broadened regime, the width of the NV's optically detected magnetic resonance (ODMR) line is proportional to the local microwave field amplitude, so mapping the linewidth maps the GHz field; Rabi oscillations at each point make that field quantitative because the Rabi frequency equals $\\gamma_{\\mathrm{NV}} B_{\\mathrm{MW}}/(2\\pi\\sqrt{2})$. Lifting the tip and fitting the height dependence to $A e^{-kd} + f_{R0}$ extracts the evanescent decay constant $k$. The companion machinery is micromagnetic simulation of the Landau-Lifshitz-Gilbert dynamics, with film disorder represented as 1 µm grains carrying ±5% variations in magnetization and anisotropy and a 5% exchange reduction at the grain boundaries; the predicted stray fields at NV height are compared pixel-by-pixel with the measurements.","core_discovery":"The central claim is that a scanning NV magnetometer can quantitatively map the GHz microwave magnetic fields produced by vortex spin-wave modes, not just the static vortex texture. In the 1 µm square, the power-broadened ODMR linewidth and the Rabi oscillation frequency trace microwave emission that spreads from the core along the Néel domain walls, identifying the vortex's wall mode. In the 6 µm disc, the static stray field alone cannot unambiguously reveal a vortex, but the microwave map shows a lobed, anisotropic field concentrated near the core that matches simulations of the azimuthal magnon mode in a disordered polycrystalline film. Quantitative Rabi scans measure a 5.5-fold enhancement near the square's core and an 11-fold enhancement at its corner relative to the retracted tip, and a 40-fold enhancement near the disc's core; height-dependent scans give evanescent decay lengths of 58-80 nm for the square's wall mode and roughly 323 nm for the disc's azimuthal mode. The paper concludes that SNVM can image vortex magnon modes at approximately 50 nm resolution, about five times finer than diffraction-limited optical techniques, and can reveal how disorder alters the spatial decay of these microwaves.","pith_inferences":["A testable extension: because the measured decay lengths differ sharply between the wall mode (~58-80 nm) and the azimuthal mode (~323 nm), fitting the height dependence at each pixel could serve as a local identifier of which vortex mode is active; the paper reports both decay lengths but does not propose this use.","The strong dependence of the decay maps on grain structure suggests SNVM evanescent-field imaging could become a non-destructive probe of microstructure: annealing a film to change grain size should measurably shift the fitted $k$ values, a prediction not tested in the paper.","The 40-fold enhancement was measured at a relatively large NV-sample separation, so combining this technique with recently demonstrated methods for reducing that separation would plausibly yield even larger enhancements; the paper notes the resolution gains possible but does not demonstrate this combination.","The paper's polarization analysis is partly confounded by frequency-dependent microwave amplitudes from the disc, so in my reading circular-polarization imaging of vortex modes needs heterodyne or frequency-mixing detection, which the authors list as future work, before it becomes a standalone claim."],"forward_implications":["A single tabletop instrument can map GHz-scale vortex magnon fields at roughly 50 nm resolution, about five times better than diffraction-limited optical imaging, without requiring a synchrotron.","Quantitative Rabi oscillation maps give local microwave field amplitudes, so the same measurement can quantify field enhancement and evanescent decay in operating magnonic devices.","The spatially varying evanescent decay constants, which differ between a wall mode and an azimuthal mode, can be imaged directly, providing a map of where a nearby qubit would couple most strongly.","Vortex-supported wall modes in a 1 µm square and azimuthal modes in a 6 µm disc can both be driven at NV-resonant frequencies near 2.85 GHz and identified by their microwave stray-field patterns.","Because the technique is substrate-agnostic and operates in ambient conditions, it can characterize samples that cannot be measured in X-ray beamlines."],"supporting_citations":[{"why":"It supplies the prior fixed-NV measurement of coupling to a dynamic ferromagnetic vortex and the comparison baseline for the field-enhancement factors reported here.","marker":"[38]"},{"why":"It establishes quantitative stray-field imaging of a vortex core, the static imaging capability this paper extends into the microwave domain.","marker":"[35]"},{"why":"It demonstrates SNVM static imaging of vortices with a single diamond spin and underpins the chirality and polarity identification used for the square.","marker":"[36]"},{"why":"It provides the nanopositioned single-spin-sensor approach to imaging spin waves that this paper adapts to power-broadened ODMR and evanescent-decay mapping.","marker":"[46]"},{"why":"It gives the analytical formulas used to convert ODMR transition frequencies into on- and off-axis static field components.","marker":"[43]"},{"why":"It supplies the power-broadening and ODMR contrast model that relates the measured linewidth to the local microwave amplitude.","marker":"[49]"},{"why":"It provides the micromagnetic solver used for all vortex dynamics and stray-field simulations in the paper.","marker":"[60]"},{"why":"It provides the Fourier-space method used to compute the simulated stray fields at arbitrary tip heights.","marker":"[31]"},{"why":"It is the prior strong-driving NV-vortex experiment whose reported enhancement at a 20 nm separation is the comparison point for the 40-fold result.","marker":"[41]"},{"why":"It reports methods for minimizing NV-sample separation that the paper cites for the technique's resolution limits and projected improvements.","marker":"[30]"}],"fun_headline_variants":["NV magnetometer images vortex microwaves at 50 nm","Tabletop NV probe maps vortex spin-wave fields at 50 nm","40-fold field boost near vortex core imaged by NV tip","Disorder-dependent vortex microwaves revealed by NV imaging","Scanning NV reveals vortex magnon modes at 50 nm"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The claim that the disc's microwave maps come from a vortex azimuthal mode, and the disorder-dependent decay conclusions, rely on a simulated disorder model whose grain size and strength were chosen to reproduce the data rather than measured on the actual sample.","fun_headline_variants_meta":{"raw":{"variants":["NV magnetometer images vortex microwaves at 50 nm","Tabletop NV probe maps vortex spin-wave fields at 50 nm","40-fold field boost near vortex core imaged by NV tip","Disorder-dependent vortex microwaves revealed by NV imaging","Scanning NV reveals vortex magnon modes at 50 nm"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000989,"raw_usage":{"total_tokens":4208,"prompt_tokens":973,"completion_tokens":3235,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":589,"completion_tokens_details":{"reasoning_tokens":3151}},"tokens_in":589,"tokens_out":3235,"duration_ms":22714,"temperature":1.0,"reasoning_tokens":3151,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-14T04:10:26.955228+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure the actual grain structure of the same 6 µm permalloy disc, for example with electron backscatter diffraction or transmission electron microscopy, and rerun the 2.85 GHz micromagnetic simulations using those measured grain sizes, orientations, and boundary exchange parameters instead of the assumed 1 µm Voronoi grains. If the simulated azimuthal-mode microwave maps and decay-length maps no longer reproduce the measured ODMR and Rabi images, the vortex-mode assignment and the disorder-dependent decay conclusions would be refuted.","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"It supplies the prior fixed-NV measurement of coupling to a dynamic ferromagnetic vortex and the comparison baseline for the field-enhancement factors reported here."},{"cited_title":"Tetienne,et al., Quantitative stray field imaging of a magnetic vortex core.Phys","cited_arxiv_id":null,"evidence_quote":"It establishes quantitative stray-field imaging of a vortex core, the static imaging capability this paper extends into the microwave domain."},{"cited_title":"Rondin,et al., Stray-field imaging of magnetic vortices with a single diamond spin.Nat","cited_arxiv_id":null,"evidence_quote":"It demonstrates SNVM static imaging of vortices with a single diamond spin and underpins the chirality and polarity identification used for the square."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"It provides the nanopositioned single-spin-sensor approach to imaging spin waves that this paper adapts to power-broadened ODMR and evanescent-decay mapping."},{"cited_title":"van der Sar, F","cited_arxiv_id":null,"evidence_quote":"It gives the analytical formulas used to convert ODMR transition frequencies into on- and off-axis static field components."},{"cited_title":"Dr ´eau,et al., Avoiding power broadening in optically detected magnetic resonance of single NV defects for enhanced dc magnetic field sensitivity.Phys","cited_arxiv_id":null,"evidence_quote":"It supplies the power-broadening and ODMR contrast model that relates the measured linewidth to the local microwave amplitude."},{"cited_title":"Vansteenkiste,et al., The design and verification of MuMax3.AIP Adv.4(10), 107133 (2014)","cited_arxiv_id":null,"evidence_quote":"It provides the micromagnetic solver used for all vortex dynamics and stray-field simulations in the paper."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"It provides the Fourier-space method used to compute the simulated stray fields at arbitrary tip heights."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"It is the prior strong-driving NV-vortex experiment whose reported enhancement at a 20 nm separation is the comparison point for the 40-fold result."},{"cited_title":"Xu,et al., Minimizing Sensor-Sample Distances in Scanning Nitrogen-Vacancy Magnetom- etry.ACS Nano19(8), 8255–8265 (2025)","cited_arxiv_id":null,"evidence_quote":"It reports methods for minimizing NV-sample separation that the paper cites for the technique's resolution limits and projected improvements."}],"review_version":1}