{"id":"353d730b-2d60-43fc-9b25-517268f43628","arxiv_id":"1908.08860","paper_version":2,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"In Ni45Co5Mn38Sn12 the martensite ground state is antiferromagnetic rather than spin glass or superparamagnetic, and in Ni44Co6Mn40Sn10 it is a superspin glass; the nanoclusters detected by SANS are structural, not magnetic.","lead":"Experiments on two nickel-cobalt-manganese-tin alloys show their low-temperature magnetic states differ from earlier reports: one is antiferromagnetic, the other a spin glass, and the nanoscale clusters seen in neutron scattering are structural, not magnetic. The work combines several measurement techniques to settle conflicting classifications in a popular family of magnetic shape-memory alloys.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Long-range AF order in Ni45Co5Mn38Sn12 rests on indirect magnetometry; the 4 K neutron diffraction is not used to identify magnetic Bragg peaks, and the Arrott plot hints at spontaneous magnetization. Direct magnetic structure evidence is needed.","rationale":"The reader's verdict was already CONDITIONAL and explicitly noted that 'long-range AF order' is asserted without direct magnetic structure evidence. My concern coincides with that point, but the reader's stated weakest_assumption was the SANS structural-cluster interpretation, whereas I identify the missing magnetic Bragg analysis as the more load-bearing issue. If the AF claim fails, the abstract's primary conclusion collapses; if the SANS cluster interpretation were wrong, the paper could still argue for AF order from magnetometry. However, because the magnetometry and AC susceptibility are strongly suggestive and the paper's own neutron data may contain unreported magnetic scattering, the appropriate response is to keep the conditional verdict and require the concrete re-analysis before upgrading. The concern does not by itself force rejection, but it does mean the central claim is currently under-verified.","tokens_in":17283,"tokens_out":4784,"duration_ms":52396,"concrete_test":"Re-analyse the 4 K neutron diffraction pattern from Fig. 3(b) against the 300 K pattern: refine with a magnetic structure model (e.g., Mn moments on the 4a/4b sites, propagation vectors k=0 and k=1/2) and test whether magnetic Bragg peaks are required by the data. If the magnetic contribution is zero within error, the 'long-range AF' claim fails and the ground state should be reclassified (e.g., SSG or phase-separated). If magnetic peaks are present, the claim is supported and the paper's conditional status can be upgraded.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The most load-bearing step is the assertion of long-range antiferromagnetic order in Ni45Co5Mn38Sn12. The evidence is entirely indirect: M-H virgin curves show a metamagnetic-like S-shape below 180 K (Sec. 3.1.4, Fig. 5(d)), and AC susceptibility fits produce unphysical SG/SPM parameters (Table 3). But the neutron diffraction experiment performed at 4 K (Sec. 3.1.3, Fig. 3(b)) is used only for structural Le Bail refinement; no magnetic Bragg peaks are reported. For a collinear or non-collinear long-range AF structure, neutron diffraction should show additional magnetic reflections or intensity changes below TN. The positive intercept in the Arrott plot (Fig. 6 inset) indicates a spontaneous magnetization, which is not expected for a pure AF and is not reconciled with the AF assignment. A field-induced metamagnetic transition can also occur in cluster-glass or phase-separated systems, so the magnetometry alone does not uniquely establish long-range order. Without a magnetic structure determination, the central claim 'long-range AF order... rule out SPM and SG' is not proven.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper investigates the low-temperature magnetic ground state of two Co-substituted Ni-Mn-Sn ferromagnetic shape memory alloys, Ni45Co5Mn38Sn12 and Ni44Co6Mn40Sn10, using DC magnetization, AC susceptibility, and small-angle neutron scattering (SANS), with supporting structural characterization by neutron diffraction and TEM. The central claims are: (i) the martensite phase of Ni45Co5Mn38Sn12 exhibits long-range antiferromagnetic (AF) order, ruling out spin-glass (SG) and superparamagnetic (SPM) behavior; (ii) Ni44Co6Mn40Sn10 instead shows a superspin-glass (SSG) ground state, contrary to an earlier SPM interpretation; and (iii) the nanometre-sized clusters detected by SANS in Ni45Co5Mn38Sn12 are structural (likely untransformed austenite) rather than magnetic, because they grow with temperature and persist beyond the magnetic transitions. The evidence for (i) includes metamagnetic-like S-shaped virgin M-H curves below 180 K, non-collapse of M vs H/T curves, a very small Mydosh parameter, unphysical parameters from SG/SPM fits, and the absence of expected SG/SPM signatures.","tokens_in":17484,"tokens_out":2569,"duration_ms":27615,"significance":"If the conclusions hold, the paper would resolve conflicting reports on the magnetic ordering in a technically important family of magnetic shape-memory alloys, with implications for understanding exchange bias, magnetocaloric effects, and the microscopic origin of SANS-observed nanoclusters. The study combines multiple complementary techniques and explicitly tests competing models (SG, SPM, AF) rather than assuming one. The systematic AC-susceptibility analysis, including Mydosh, critical slowing-down, Vogel-Fulcher, and Néel-Arrhenius fits, is a useful template for classifying low-temperature magnetic states in martensitic Heusler alloys. The SANS analysis with quantitative size distributions and volume-fraction evolution is also careful and reproducible. However, the strength of the claim of long-range AF order and the structural assignment of the SANS clusters exceed what the presented data can unambiguously support, as detailed below.","major_comments":[{"comment":"The Arrott plot shown in the inset of Fig. 6 exhibits a positive intercept of the extrapolated high-field M² vs H/M curves, which the authors interpret as evidence of spontaneous magnetization. This is difficult to reconcile with a purely antiferromagnetic ground state, and the paper does not explain how a spontaneous moment coexists with the claimed long-range AF order in Ni45Co5Mn38Sn12. The authors mention a weak ferromagnetic contribution at higher temperatures (§3.1.4, around 225 K), but the magnitude and temperature evolution of this FM component in the AF state are not quantified or separated from the AF response. This ambiguity weakens the unambiguous assignment of a pure AF ground state and should be addressed, for example by analyzing the field dependence of the metamagnetic transition and the high-field slope of the Arrott plot.","section":"§3.1.4, Fig. 6 inset"},{"comment":"The neutron diffraction experiment performed at 4 K is used only for structural Le-Bail refinement of the martensite phase; no magnetic Bragg peaks, magnetic symmetry analysis, or comparison of 4 K and 300 K patterns is reported. For a long-range antiferromagnet, additional magnetic reflections or distinct intensity changes should be visible in the neutron diffraction data. Without this direct evidence, the claim of 'long-range AF order' in Ni45Co5Mn38Sn12 is inferred solely from magnetometry and AC susceptibility, which can mimic AF behavior in phase-separated or cluster-glass systems. The authors should either analyze the existing 4 K neutron data for magnetic scattering or explicitly soften the conclusion to 'AF-like correlations' or 'a metamagnetic ground state consistent with short-range or clustered AF order.'","section":"§3.1.3"},{"comment":"The assignment of the SANS-detected nanoclusters to structural (untransformed austenite) rather than magnetic origin rests almost entirely on the observation that they grow with temperature and persist above Tf and TCA. However, the SANS data were collected in zero field and the total scattering cross-section was modeled without separating nuclear and magnetic contributions. The authors' premise, stated in §4 as 'If the clusters are of magnetic origin, they should have shown some significant changes across any of the magnetic transition,' is not a necessary consequence: magnetic clusters can persist and even grow if their size is governed by chemical or structural chemical ordering, or if inter-cluster interactions change with temperature. To robustly support the structural interpretation, the authors should perform polarized SANS or measure in a saturating magnetic field to isolate the magnetic scattering, or at least explicitly discuss why the temperature evolution alone is conclusive.","section":"§4, SANS discussion"},{"comment":"For Ni44Co6Mn40Sn10, the conclusion of an SSG ground state is based on AC-susceptibility parameters (Φ=0.027, zν=10.7, τ0=6.3×10⁻¹³ s) that fall in the expected SSG range. However, the low-field M-H data in Fig. 11(b) show weak S-shaped curves at 5, 20, and 40 K, which the authors describe as 'a weak AF order in this temperature range,' and the text states that above 40 K a FM behavior appears. The coexistence of weak AF order, a spontaneous magnetization (from the Arrott plot in Fig. 12 inset), and SSG dynamics in the same temperature range is not self-evidently consistent, and the paper does not explain how these observations coexist. Since the paper explicitly claims SSG as the ground state, the relationship between the weak AF-like features and the freezing transition should be clarified, or the claim should be qualified.","section":"§3.2, Table 3"}],"minor_comments":[{"comment":"The abstract says 'provide a clear evidence' and 'rule out SPM and SG orders' for Ni45Co5Mn38Sn12, but the evidence is indirect; rephrasing to 'consistent with AF order' or 'strong evidence against SPM and SG' would better match the experimental support.","section":"Abstract"},{"comment":"The displayed equation for the SANS intensity contains corrupted characters ('drrqSrVrNrqPnqI pt') and is difficult to read; the authors should typeset it properly and define all symbols consistently.","section":"Equation (6)"},{"comment":"The table is referred to as both 'Table 3' and 'Table III' in the text; please use a consistent numbering style throughout.","section":"Table 3 / text"},{"comment":"The caption of Fig. 7(b) uses both TP and Tf inconsistently; the variables should be defined clearly, especially because the text around equations (2)-(4) uses Tf for the zero-frequency freezing temperature while the fits use TP.","section":"§3.1.4, Fig. 7"},{"comment":"Some references are incomplete or inconsistent (e.g., Ref. [12] lists only an incomplete author list, and Refs. [44] and [60] appear with irregular formatting); the authors should proofread the reference list.","section":"References"}],"recommendation":"major_revision","confidential_remarks":null},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Here is my honest read. The most valuable thing in this paper is the SANS analysis: the nanocluster peak that Bhatti et al. took as magnetic spin clusters grows with temperature and persists above Tf and through the martensite transition. The authors are right that this is hard to square with a magnetic origin, and their structural interpretation (untransformed austenite) is credible. That alone is worth publishing, even if it is a correction to a prior SANS assignment.\n\nThe second useful piece is the magnetometry. For Ni45Co5Mn38Sn12, the non-collapse of M versus H/T, the tiny Mydosh parameter, and the physically absurd spin-glass fitting parameters together rule out SPM and ordinary SG quite convincingly. For Ni44Co6Mn40Sn10, the AC susceptibility parameters fall in the SSG range, so the claim that it is a superspin glass rather than SPM is reasonably supported. The paper does what a good experimental correction should do: it repeats the composition in question, checks transformation temperatures are similar, and directly addresses the contradiction.\n\nWhere it overreaches is the long-range AF claim. The evidence is all indirect. The metamagnetic S-shape in the virgin curves is real, but similar behavior can appear in cluster-glass or phase-separated systems. The Arrott plot apparently shows a positive intercept, which implies spontaneous magnetization—not what you expect for a pure antiferromagnet, and the paper never reconciles that. The neutron diffraction measured at 4 K was used only for structural Le Bail refinement; no magnetic Bragg peaks are reported. So 'long-range AF order, proven unambiguously' is not what the data show. It is a reasonable hypothesis, but the conclusion needs to be softened or backed by magnetic diffraction. The stress-test note is correct on this point.\n\nThe SANS structural conclusion is also not watertight, since the total cross-section was fitted and there is no nuclear/magnetic separation. But the thermal behavior is as argued; I would not call that a fatal flaw, just a limitation that should be stated more carefully. The fitted parameters lack error bars, which is a minor presentation issue given that the unphysical values are the point.\n\nWho gets value from this? Experimentalists working on Ni-Mn-Sn and related FSMAs, especially anyone using SANS to look for spin clusters. This is a within-subfield correction, not a breakthrough, but it deserves a serious referee. I would send it to review, asking to revise the AF claim and to address the Arrott inconsistency. If the authors can add a magnetic structure determination, it would be a strong paper; without it, the central claim should be presented as consistent with AF, not proof.","headline":"The SANS reinterpretation is the real contribution; the long-range AF claim is asserted beyond what the magnetometry can prove.","tokens_in":18101,"tokens_out":2474,"would_cite":true,"duration_ms":26417,"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":"For one Ni-Co-Mn-Sn alloy, the low-temperature martensite is a long-range antiferromagnet, and the nanoclusters seen by SANS are structural, not spin clusters.","keywords":["ferromagnetic shape memory alloys","Ni-Mn-Sn Heusler alloys","martensite","antiferromagnetism","spin glass","superparamagnetism","small-angle neutron scattering","AC susceptibility"],"falsifier":"Run small-angle neutron scattering with polarization analysis, or with an applied magnetic field, on Ni45Co5Mn38Sn12 across Tf and TCA: if the correlation peak near q about 0.05 inverse angstroms has no magnetic scattering component and survives into the paramagnetic austenite, the structural assignment is confirmed; if the magnetic scattering tracks the cluster peak or disappears at the magnetic transitions, the claim fails.","tokens_in":17039,"feed_emoji":"🧲","tokens_out":7827,"duration_ms":72688,"temperature":0.7,"pith_summary":"This paper addresses a long-standing dispute about the magnetic ground state of the low-temperature martensite phase in Co-substituted Ni-Mn-Sn shape-memory alloys. Using DC magnetization, frequency-dependent AC susceptibility, and small-angle neutron scattering, it concludes that Ni45Co5Mn38Sn12 is a long-range antiferromagnet below about 180 K, not a spin glass or superparamagnet. For the neighboring composition Ni44Co6Mn40Sn10, the same analysis gives a superspin-glass state at low temperature, contradicting an earlier superparamagnetism assignment. The paper also argues that the nanometre-scale clusters visible in SANS are structural leftovers of untransformed austenite, not magnetic spin clusters, since they grow with temperature and persist across the magnetic transitions. If correct, this would settle how similar magnetization and SANS data should be interpreted across the Ni-Mn-Sn family.","feed_headline":"Martensite in Ni-Co-Mn-Sn alloy is antiferromagnetic, not spin glass","feed_subtitle":"Magnetometry and neutron scattering rule out spin-glass order; the SANS nanoclusters are structural, not magnetic.","key_machinery":"The load-bearing evidence is the frequency-dependent AC-susceptibility peak combined with the low-field virgin magnetization isotherms. The AC peak is analysed through four standard dynamical models, the Mydosh frequency shift, critical slowing down, Vogel-Fulcher, and Neel-Arrhenius, whose fitted parameters are compared with canonical ranges for spin glass, cluster glass, and superparamagnetism; the unphysical fitted values in the first alloy and the canonical superspin-glass values in the second decide the classification. In parallel, the metamagnetic jump in the virgin M-H loops below 180 K identifies the antiferromagnetic ground state directly. The SANS analysis uses a spherical form-factor model with a log-normal size distribution under the local monodisperse approximation, with the correlation peak and its temperature evolution used to characterise the nanoclusters; the distinction between magnetic and structural origin rests on the temperature dependence of cluster size and volume fraction rather than on separating nuclear and magnetic scattering.","core_discovery":"The central claim is that the low-temperature martensite in Ni45Co5Mn38Sn12 carries long-range antiferromagnetic order, established by a metamagnetic transition in the virgin magnetization isotherms below 180 K and by AC-susceptibility dynamics whose fitted parameters (Mydosh shift of 0.0017, critical-slowing-down exponent of 249.7, and microscopic attempt times near $10^{-43}$ to $10^{-99}$ s) fall far outside the canonical ranges for spin glasses and superparamagnets. On this basis the paper rules out both spin-glass and superparamagnetic ground states for this composition. For Ni44Co6Mn40Sn10, the same battery of tests yields parameters consistent with a canonical superspin glass, so the earlier superparamagnetism interpretation is replaced by superspin-glass freezing. The SANS correlation peak near q about 0.05 inverse angstroms is assigned to nanometre-scale structural clusters, most plausibly untransformed austenite, rather than to magnetic spin clusters, because the clusters grow from about 3 nm at 30 K to 11 nm at 300 K and survive above the freezing and Curie temperatures.","pith_inferences":["If the structural-cluster interpretation holds generally, earlier SANS-only spin-cluster assignments in other Ni-Mn-based shape-memory alloys would need re-examination with AC-susceptibility or polarized-neutron checks before being accepted.","A direct test would be field-dependent or polarized SANS: if the correlation peak survives with unchanged intensity in the non-magnetic nuclear channel and disappears from the magnetic channel, the structural origin is confirmed; this is an extension the paper did not perform.","The observed coarsening of the nanoclusters with temperature, with large clusters growing at the expense of small ones, resembles Ostwald ripening and could be used as a probe of local martensitic-transformation kinetics through thermal cycling.","Compositional tuning of e/a may offer a practical route to select between antiferromagnetic and superspin-glass ground states in this alloy family, a consequence only implicit in the paper's comparison."],"forward_implications":["In Ni45Co5Mn38Sn12, the martensite phase is antiferromagnetic at low temperature; the ZFC/FC bifurcation and the 165 K peak in the ZFC curve are not evidence for spin-glass or superparamagnetic freezing.","The nanometre-sized clusters detected by SANS in these alloys should not automatically be taken as magnetic spin clusters; their growth from about 3 nm to about 11 nm with rising temperature and their persistence above Tf and TCA point to untransformed austenite.","Ni44Co6Mn40Sn10 has a superspin-glass ground state at low temperature rather than the superparamagnetic state assigned in an earlier SANS-based study.","The antiferromagnetic-versus-superspin-glass difference between the two compositions tracks the electron-per-atom ratio e/a, connecting magnetic ground state to composition in the Co-doped Ni-Mn-Sn system.","Combining AC susceptibility with SANS resolves ambiguous low-temperature magnetism in ferromagnetic shape-memory alloys where magnetization alone cannot distinguish antiferromagnetic order from cluster freezing."],"supporting_citations":[{"why":"Earlier SANS and magnetization study of Ni44Co6Mn40Sn10 and Ni42Co8Mn40Sn10 reporting superparamagnetic spin clusters; the paper's main experimental baseline to contradict.","marker":"[29]"},{"why":"Report of long-range antiferromagnetic ordering in ternary Ni50Mn37Sn13, used as the precedent for antiferromagnetic martensite in Ni-Mn-Sn.","marker":"[16]"},{"why":"Companion report of antiferromagnetic ordering in Ni50Mn40Sb10, supporting the antiferromagnetic interpretation for related martensites.","marker":"[17]"},{"why":"Review providing canonical spin-glass relaxation ranges used to judge whether the fitted dynamics parameters are physical.","marker":"[31]"},{"why":"Monograph defining spin-glass and superparamagnetic frequency-shift and relaxation criteria used throughout the analysis.","marker":"[32]"},{"why":"Earlier study reporting superspin-glass freezing below Tf in a closely related Co-doped Ni-Mn-Sn alloy, used as a comparison for Ni44Co6Mn40Sn10.","marker":"[27]"},{"why":"Source of the local monodisperse approximation used to fit the SANS data with spherical particles and a log-normal size distribution.","marker":"[57]"}],"fun_headline_variants":["AF order in Ni-Co-Mn-Sn martensite, not spin glass","SANS nanoclusters structural, not magnetic, in Ni-Co-Mn-Sn","Ni44Co6Mn40Sn10 freezes as superspin glass, not SPM","Two Ni-Co-Mn-Sn alloys: one AF, one superspin glass","Martensite AF order confirmed; SPM ruled out in Ni-Co-Mn-Sn"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The conclusion that the SANS-detected nanoclusters are structural rather than magnetic rests on the premise that their growth with temperature and persistence across the magnetic transitions are enough to prove they are not magnetic; the experiment did not separately measure nuclear and magnetic scattering, so a hypothetical magnetic cluster population that also grew and persisted would not be ruled out.","fun_headline_variants_meta":{"raw":{"variants":["AF order in Ni-Co-Mn-Sn martensite, not spin glass","SANS nanoclusters structural, not magnetic, in Ni-Co-Mn-Sn","Ni44Co6Mn40Sn10 freezes as superspin glass, not SPM","Two Ni-Co-Mn-Sn alloys: one AF, one superspin glass","Martensite AF order confirmed; SPM ruled out in Ni-Co-Mn-Sn"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000227,"raw_usage":{"total_tokens":1485,"prompt_tokens":974,"completion_tokens":511,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":590,"completion_tokens_details":{"reasoning_tokens":400}},"tokens_in":590,"tokens_out":511,"duration_ms":5334,"temperature":1.0,"reasoning_tokens":400,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-14T11:27:53.678492+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Run small-angle neutron scattering with polarization analysis, or with an applied magnetic field, on Ni45Co5Mn38Sn12 across Tf and TCA: if the correlation peak near q about 0.05 inverse angstroms has no magnetic scattering component and survives into the paramagnetic austenite, the structural assignment is confirmed; if the magnetic scattering tracks the cluster peak or disappears at the magnetic transitions, the claim fails.","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Earlier SANS and magnetization study of Ni44Co6Mn40Sn10 and Ni42Co8Mn40Sn10 reporting superparamagnetic spin clusters; the paper's main experimental baseline to contradict."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Report of long-range antiferromagnetic ordering in ternary Ni50Mn37Sn13, used as the precedent for antiferromagnetic martensite in Ni-Mn-Sn."},{"cited_title":"Phys.: Condens","cited_arxiv_id":null,"evidence_quote":"Companion report of antiferromagnetic ordering in Ni50Mn40Sb10, supporting the antiferromagnetic interpretation for related martensites."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Review providing canonical spin-glass relaxation ranges used to judge whether the fitted dynamics parameters are physical."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Monograph defining spin-glass and superparamagnetic frequency-shift and relaxation criteria used throughout the analysis."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Earlier study reporting superspin-glass freezing below Tf in a closely related Co-doped Ni-Mn-Sn alloy, used as a comparison for Ni44Co6Mn40Sn10."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Source of the local monodisperse approximation used to fit the SANS data with spherical particles and a log-normal size distribution."}],"review_version":1}