{"id":"08199b24-ad40-41ee-b1ea-0fd6cc95f20b","arxiv_id":"2412.02272","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":7.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"Co8Zn9Mn3 shows nonreciprocal resistivity from two coexisting mechanisms, spin-chirality scattering near the Curie temperature and conical-spin band asymmetry at low temperature.","lead":"A chiral magnet whose magnetic order survives to about 300 K shows electrical resistance that depends on the direction of current flow, and the authors split this nonreciprocal signal into two physically different pieces. The separation connects one piece to spin-chirality scattering and the other to asymmetry of the electronic bands in the conical magnetic state.","discovery_kind":"first_principles","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The separation into r2f_band and r2f_scat is enforced by anchoring r2f_band=0 at high field and by normalizing alpha to M(0.1 T), which is not a saturated state at low temperatures.","rationale":"I read the paper as a careful attempt to separate two nonreciprocal-resistivity mechanisms using a physically motivated but assumption-laden decomposition. The reader's weakest assumption correctly identifies the decomposition rule as the load-bearing point. My stress-test sharpens one specific unverified anchor in that rule: the extraction of alpha(B) from M(B)/M(0.1 T) presupposes that 0.1 T is a saturation field at 10 K, which is inconsistent with the reported low-temperature rise of Bc. This makes the theoretical prediction in Fig. 4(c) and the definition of r2f_band mutually dependent in a way that has not been checked. The concern is concrete and testable, but it does not overturn the paper's positive evidence: the linear-in-current bias dependence, the opposite signs of the two contributions, the qualitative T-dependence below and above Tc, and the independent magnon-chirality calculation all support a real two-component structure. The issue is that the quantitative decomposition is not yet robust. Therefore the existing conditional verdict is appropriate; I recommend keeping it unchanged while requiring the proposed normalization check, or an equivalent independent determination of M_sat and A_scat, for acceptance.","tokens_in":18609,"tokens_out":6069,"duration_ms":69768,"concrete_test":"Using the already-collected 10 K M(B) and rxx,2f(B) data, recompute the decomposition without anchoring r2f_band to zero at 0.1 T: obtain M_sat from the forced-FM plateau above Bc(10 K), set cos(alpha(B)) = M(B)/M_sat, and replot Eq. (7) together with the residual rxx,2f - A_scat(T) M(B). If the theoretical curve no longer vanishes above 0.1 T, or if the residual stays finite throughout the forced-ferromagnetic regime, the reconstruction in Eq. (1) is not self-consistent and the claimed separation into two distinct mechanisms loses support.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The load-bearing step is the extraction of r2f_band in Eq. (1) and its theoretical comparison in Fig. 4(c). A_scat(T) is fixed by requiring r2f_band to vanish in the large-field limit, so the statement that r2f_band appears only in the conical state and is absent in the forced-ferromagnetic state is built into the analysis rather than tested. The specific flaw is in Fig. S12: cos(alpha(B)) is defined as M(B)/M(0.1 T), 'by assuming the saturation of M as at B=0.1 T,' but the phase diagram in Figs. 1(b) and S3 shows Bc and BH-C rising steeply below 100 K; at 10 K, 0.1 T is very likely not in the forced-ferromagnetic state. Thus alpha(0.1 T) is not 0, and the theoretical r2f_band proportional to cos(alpha) sin^2(alpha) from Eq. (7) is not required to vanish above 0.1 T. The residual above 0.1 T that the authors attribute to the empirical form of r2f_scat could instead be the band term surviving because the assumed normalization is wrong; conversely, subtracting a component proportional to an unsaturated M(B) can manufacture a band-like contribution in the conical region. The central claim that the two mechanisms are separated in a single material therefore rests on an unverified normalization rather than on an independent measurement. A secondary concern is Eq. (2): at 295-300 K, i.e. below Tc=301 K, the entire signal is assigned to r2f_scat by sign without a quantitative test for a possible surviving band contribution.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript reports measurements of nonreciprocal (second-harmonic) resistivity in the chiral magnet Co8Zn9Mn3 over a wide temperature range, including above room temperature. The authors observe a field- and temperature-dependent signal and decompose it into two components: a scattering contribution r2f_scat that is assumed proportional to the magnetization for T<290 K and dominant near Tc, and a band-asymmetry contribution r2f_band that appears in the conical state and persists to low temperature. A Kondo-lattice model with a conical spin structure yields a theoretical r2f_band proportional to cos(alpha) sin^2(alpha), and a magnon calculation yields r2f_scat ~ T^(3/2) at low temperatures. The central claim is that these two microscopic mechanisms are separated and identified in a single room-temperature chiral magnet.","tokens_in":18996,"tokens_out":4276,"duration_ms":40769,"significance":"If the decomposition were independently validated, this paper would be a significant contribution: it would demonstrate the coexistence and separation of scattering-based and band-based nonreciprocal transport in a single material with a quantitative theoretical framework. The experimental dataset is extensive, the exclusion of the spurious I x B component via polar-angle measurements is careful, and the Boltzmann-theory derivation of the band-asymmetry term, including the exact diagonalization of the Kondo-lattice Hamiltonian, is a useful theoretical contribution. However, the central decomposition rests on an assumption that is not directly measured, and the theoretical comparisons involve fitted or assumed normalizations, so the mechanism identification is less secure than the text suggests.","major_comments":[{"comment":"The decomposition rxx,2f = r2f_scat + r2f_band is imposed rather than measured. The text states that the sign and normalization of r2f_scat is determined with the assumption that r2f_band vanishes in the large-field limit; with that anchor, r2f_band is defined as the residual. Consequently, the statement that r2f_band appears only in the conical state and is absent in the forced-ferromagnetic state is built into the analysis, not tested. An independent determination of r2f_scat (for example, from a measurement in a clearly saturated forced-ferromagnetic state at fields well above Bc, or from a microscopic calculation of the scattering term without the M-proportionality ansatz) is needed to support the central claim.","section":"Main text, Eq. (1) and following paragraph"},{"comment":"The theoretical comparison uses alpha(B) extracted from cos alpha(B) = M(B)/M(0.1 T), with the assumption that M is saturated at 0.1 T. Figs. 1(b) and S3 show that Bc and BH-C rise steeply below 100 K; at 10 K, 0.1 T is very likely inside the conical or helical state, so alpha(0.1 T) is not zero. The theoretical r2f_band proportional to cos(alpha) sin^2(alpha) is then not required to vanish for B > 0.1 T. The residual signal above 0.1 T, which the authors attribute to the empirical form of r2f_scat, could instead be a band term that persists because of an incorrect normalization. Conversely, subtracting an M-proportional term using an unsaturated M(B) can generate an artificial band-like contribution in the conical region. This normalization is load-bearing for the mechanism identification.","section":"Fig. S12 and Eq. (7)"},{"comment":"The magnon comparison is not parameter-free: the blue dotted curve in Fig. 4(d) is obtained by a least-squares fit of rho_scat = c T^(3/2) to the experimental data, with c chosen to match the data. The statement that the T^(3/2) curve agrees with experiment therefore does not constitute an independent quantitative test of the scattering mechanism; it shows only that the data are consistent with a T^(3/2) law after choosing the overall scale. A prediction of the absolute magnitude, or an independent determination of c from known material parameters, would strengthen the identification.","section":"Fig. 4(d) and SI D-4.4"},{"comment":"For T > 290 K (that is, below Tc = 301 K), the entire measured rxx,2f is assigned to r2f_scat based on the sign of the signal, with no quantitative test for a possible surviving band contribution. Since the band-asymmetry term is argued to exist in the conical state for all T < Tc, a coexistence of the two components in the 295-300 K range is plausible and should be ruled out by a fit or a bound rather than by inspection of sign alone.","section":"Main text, Eq. (2)"}],"minor_comments":[{"comment":"Reference [4] contains a typo: 'Annual Review and of Condensed and Matter Physics' should be 'Annual Review of Condensed Matter Physics'.","section":"References"},{"comment":"The notation for the nonreciprocal resistivity switches between rxx,2f in the main text and rho_2f in the Supplementary Information; please unify the notation across the manuscript.","section":"Notation"},{"comment":"The caption states that the theoretical curve reproduces the trend, but the curve is normalized to the experimental data; please state the normalization explicitly in the caption.","section":"Fig. 4(c) caption"},{"comment":"The sentence describing the determination of r2f_scat should specify the exact large-field limit used (which field value), because the resulting decomposition depends on that choice.","section":"Main text, after Eq. (1)"},{"comment":"The numerical value 3.47 in Eq. (D23) is quoted without derivation; a brief explanation of the integration method or a reference would improve reproducibility.","section":"SI D-4.4, Eq. (D23)"}],"recommendation":"major_revision","confidential_remarks":"The paper contains high-quality transport data and a useful theoretical framework, but the central mechanism separation is based on an unverified decomposition. If the authors can provide independent evidence for the decomposition—for example, high-field measurements in a clearly saturated forced-ferromagnetic state, or a calculation of the scattering term that does not assume strict proportionality to M—the paper would be suitable for publication in this journal. As written, the claim of having 'successfully separated' the two mechanisms is stronger than the supporting evidence warrants."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Here is my take. The new thing is that Co8Zn9Mn3 shows nonreciprocal resistivity at room temperature, and the authors try to separate two contributions: a scattering term tied to M, and a band-asymmetry term tied to the conical state. They even derive the band term from a Kondo-lattice model, getting the cos(alpha) sin^2(alpha) form. That derivation is real work, and the experimental data are clean and internally consistent.\n\nThe soft spot is the separation itself. Below 290 K they set r2f_scat = A_scat(T) M(T,B), with A_scat chosen so that r2f_band vanishes at high field. That means the claim that r2f_band exists only in the conical state and disappears in the forced ferromagnetic state is built into the procedure, not tested by it. The stress-test note sharpens this: in Fig. S12 they define cos alpha(B) = M(B)/M(0.1 T) by assuming the magnetization is saturated at 0.1 T. The phase diagram shows Bc rising steeply below 100 K, so at 10 K, 0.1 T is not necessarily the forced ferromagnetic state. If alpha(0.1 T) is nonzero, the theoretical r2f_band does not have to vanish above 0.1 T, and the residual they attribute to the empirical form of r2f_scat could be a band term with the wrong normalization. The paper acknowledges a residual mismatch, but it is attributed to the scattering form, not to the possibility that the band term is misnormalized. So the central decomposition is plausible but not established.\n\nThe magnon comparison has the same pattern: the T^(3/2) curve is fitted with a coefficient c, so it is not a parameter-free prediction. This is a secondary concern; the temperature dependence still looks right.\n\nWhat the paper does well: the current-linear check, careful handling of the field-angle-dependent I x B component, honest reporting of the residual, and a transparent derivation. The authors are not overselling; Section D-4.4 says the fit may be attributed to magnons, which is appropriately cautious.\n\nBottom line: this deserves a serious referee. A good referee would ask for a harder test of the decomposition—for example, alpha(B) from a field well into the forced ferromagnetic state, or a comparison where the normalization is not shared between experiment and theory. If those tests land, the paper becomes a strong result. As it is, it is a very good candidate that needs revision, not rejection.","headline":"Room-temperature nonreciprocal transport with a plausible but imposed two-component separation; worth a serious referee, not a desk reject.","tokens_in":19561,"tokens_out":3377,"would_cite":true,"duration_ms":34905,"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":"This paper claims that the nonreciprocal resistivity of the chiral magnet Co8Zn9Mn3 decomposes into two distinct components, one from chiral spin scattering and one from conical-state band asymmetry.","keywords":["nonreciprocal transport","electrical magnetochiral effect","chiral magnet","conical spin state","spin chirality","band asymmetry","Co-Zn-Mn","second harmonic resistivity"],"falsifier":"Measure $r_{xx,2f}$ at fixed temperature below 100 K from the conical phase through $B_c$ into the forced ferromagnetic state. The paper's identification predicts that the band term follows $\\cos\\alpha(B) \\sin^2\\alpha(B)$ inside the conical phase and drops to zero above $B_c$, while the scattering term contributes a $T^{3/2}$ background; a clear field-dependent nonreciprocal signal above $B_c$ at low temperature, or a deviation of $r_{2f}^{\\mathrm{scat}}$ from strict proportionality to $M(T,B)$ at intermediate fields, would break the decomposition and falsify the two-mechanism assignment.","tokens_in":2088,"feed_emoji":"🧲","tokens_out":2208,"duration_ms":79413,"temperature":0.7,"pith_summary":"This paper reports that the nonreciprocal (direction-dependent) electrical resistivity of the chiral magnet Co8Zn9Mn3 contains two physically distinct contributions that can be separated by their magnetic-field and temperature dependence. One contribution, largest just above the Curie temperature and vanishing toward zero temperature, comes from asymmetric scattering of electrons off chiral spin fluctuations (magnons below Tc, critical spin clusters above Tc). The other, which appears in the conical spin state and survives at the lowest temperatures, comes from an asymmetry in the electronic band dispersion induced by the exchange coupling between conduction electrons and the conical spin texture. Using a Kondo-lattice model and Boltzmann transport theory, the paper derives a closed-form expression for the band term and shows it scales as $\\cos\\alpha \\sin^2\\alpha$, where $\\alpha$ is the tilt angle of the conical magnetization. Because both mechanisms appear in one material, the experiment provides a clean platform for studying nonreciprocal transport at and above room temperature.","feed_headline":"Two nonreciprocal transport mechanisms separated in one chiral magnet","feed_subtitle":"Chiral spin fluctuations dominate near Tc; conical-state band asymmetry persists to zero temperature.","key_machinery":"The central construct is the additive decomposition $r_{xx,2f}(T,B) = r_{2f}^{\\mathrm{scat}}(T,B) + r_{2f}^{\\mathrm{band}}(T,B)$, with the scattering part fixed as $r_{2f}^{\\mathrm{scat}}(T,B) = A_{\\mathrm{scat}}(T) M(T,B)$ below 290 K and the band part defined as the remainder, normalized so that it vanishes in the high-field forced-ferromagnetic limit. The theory is built on a Kondo-lattice Hamiltonian for conduction electrons coupled to a conical spin texture, and the Boltzmann equation with a single relaxation time is expanded to second order in the electric field. For the band term this yields the closed identity $r_{2f}^{\\mathrm{band}} \\propto \\cos\\alpha(B) \\sin^2\\alpha(B)$, where $\\alpha$ is the tilt angle of the conical magnetization defined by $\\cos\\alpha = M(B)/M_{\\mathrm{sat}}$; the same framework, with the Dzyaloshinskii-Moriya interaction treated perturbatively, produces the magnon-induced vector-chirality scattering with a $T^{3/2}$ low-temperature law. The decomposition rule is what lets the experiment separate the two mechanisms.","core_discovery":"The central claim is that the measured nonreciprocal resistivity $r_{xx,2f}$ in Co8Zn9Mn3 is the sum of two components with different physical origins. For $T < 290$ K, the paper decomposes $r_{xx,2f} = r_{2f}^{\\mathrm{scat}} + r_{2f}^{\\mathrm{band}}$, where $r_{2f}^{\\mathrm{scat}}$ is assumed proportional to the magnetization $M(T,B)$ and $r_{2f}^{\\mathrm{band}}$ is the remainder; the normalization is fixed by requiring the band term to vanish in the forced ferromagnetic state at high field. For $T > 290$ K, the entire signal is assigned to $r_{2f}^{\\mathrm{scat}}$. The identified scattering term peaks near $T_c = 301$ K, follows the magnetization's field dependence, and is explained by magnon-induced vector spin chirality (with a $T^{3/2}$ low-temperature law) and by critical chiral spin-cluster fluctuations above $T_c$. The band term is largest in the conical phase, persists to zero temperature at roughly half its maximum, and is reproduced by the zero-temperature Boltzmann formula $r_{2f}^{\\mathrm{band}} \\propto \\cos\\alpha \\sin^2\\alpha$, reflecting the tilt angle of the conical magnetization. The paper concludes that these are the same two mechanisms long discussed separately in chiral magnets, here separated in one room-temperature material.","pith_inferences":["If the decomposition is correct, then $r_{2f}^{\\mathrm{scat}}(T,B)/M(T,B)$ should be a function of temperature only below 290 K; checking this directly on a denser field grid would test the proportionality assumption without relying on the high-field limit.","The paper's result $r_{2f}^{\\mathrm{band}} \\propto \\cos\\alpha \\sin^2\\alpha \\propto M\\langle\\chi_{\\mathrm{vec}}\\rangle$ suggests that both the band-asymmetry and scattering mechanisms may be governed by the same vector-chirality order parameter, so materials with larger helical pitch or stronger DMI could be screened by measuring this single scaling.","The observed $\\mathbf{j}\\times\\mathbf{B}$ component, which the authors assign to the electrode interface, implies that nonreciprocal measurements on microdevices can mix intrinsic bulk signals with surface or Rashba-type contributions; angle-dependent checks are necessary for quantitative separation in other materials."],"forward_implications":["The two mechanisms can be separated in a single material because they occupy different field and temperature regimes: the scattering term peaks near $T_c$ and vanishes at zero temperature, while the band term lives in the conical state and survives to zero temperature.","The band term's field dependence is tied directly to the tilt angle of the conical magnetization through $\\cos\\alpha \\sin^2\\alpha$, so nonreciprocal transport can be used as a probe of the conical state's structure.","Nonreciprocal resistivity is not always a fluctuation or scattering phenomenon: the conical-state band asymmetry produces a finite signal even in the zero-temperature limit.","Below $T_c$, the scattering component is consistent with magnon-induced vector spin chirality, reproducing the experimentally observed $T^{3/2}$ growth at low temperatures.","Above $T_c$, the same scattering channel is driven by critical spin fluctuations with finite vector chirality, analogous to the behavior reported in MnSi."],"supporting_citations":[{"why":"Provides the MnSi benchmark where nonreciprocal resistivity is dominated by chiral spin fluctuations near Tc; the paper compares its scattering component to this behavior.","marker":"[9]"},{"why":"Supplies the theory of nonreciprocal scattering from chiral spin-cluster fluctuations used to identify r2f_scat above Tc.","marker":"[13]"},{"why":"Supplies the Boltzmann-transport framework for second-order resistivity used to derive the band-asymmetry formula.","marker":"[8]"},{"why":"Provides the nonlinear Boltzmann formalism for second-harmonic current used in the derivation of the band term.","marker":"[27]"},{"why":"Reports multiple components of nonreciprocal resistivity in the chiral magnet CrNb3S6, including a band-asymmetry assignment that this paper puts on theoretical footing.","marker":"[10]"},{"why":"Documents the magnetic disorder and short-range antiferromagnetic correlations of Mn spins invoked to explain the suppression of the band term below 100 K.","marker":"[17]"},{"why":"Establishes Co-Zn-Mn as a chiral magnet hosting skyrmions beyond room temperature, the material family used here.","marker":"[15]"}],"fun_headline_variants":["Chiral magnet reveals two distinct nonreciprocal transport mechanisms","Room-temperature separation of two nonreciprocal transport channels","Nonreciprocal transport: two mechanisms identified in one material","Two origins of nonreciprocal resistivity in a room-temperature chiral magnet","Two nonreciprocal transport effects separated in a chiral magnet"],"cache_read_input_tokens":21504,"weakest_assumption_plain":"The decomposition rests on assuming that below 290 K the scattering component is strictly proportional to magnetization with a coefficient fixed by demanding the band component vanish at high field, and that above 290 K the entire signal is scattering; if either assumption fails, the reconstructed band component is an artifact.","fun_headline_variants_meta":{"raw":{"variants":["Chiral magnet reveals two distinct nonreciprocal transport mechanisms","Room-temperature separation of two nonreciprocal transport channels","Nonreciprocal transport: two mechanisms identified in one material","Two origins of nonreciprocal resistivity in a room-temperature chiral magnet","Two nonreciprocal transport effects separated in a chiral magnet"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000502,"raw_usage":{"total_tokens":2471,"prompt_tokens":981,"completion_tokens":1490,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":597,"completion_tokens_details":{"reasoning_tokens":1408}},"tokens_in":597,"tokens_out":1490,"duration_ms":11458,"temperature":1.0,"reasoning_tokens":1408,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-11T23:39:58.895299+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure $r_{xx,2f}$ at fixed temperature below 100 K from the conical phase through $B_c$ into the forced ferromagnetic state. The paper's identification predicts that the band term follows $\\cos\\alpha(B) \\sin^2\\alpha(B)$ inside the conical phase and drops to zero above $B_c$, while the scattering term contributes a $T^{3/2}$ background; a clear field-dependent nonreciprocal signal above $B_c$ at low temperature, or a deviation of $r_{2f}^{\\mathrm{scat}}$ from strict proportionality to $M(T,B)$ at intermediate fields, would break the decomposition and falsify the two-mechanism assignment.","supporting_citations":[],"review_version":1}