{"id":"60de3314-b858-41bc-b92c-e8ec99f3d2c5","arxiv_id":"2504.15966","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":10,"one_line_summary":"HoB4 hosts a previously unreported in-plane ordered phase near its critical boundary, and simulations suggest out-of-plane couplings and defects can produce such in-plane order and extra plateaus.","lead":"This paper reports neutron and magnetization measurements on the frustrated magnet HoB4, finding a new magnetic phase with in-plane order that appears in a narrow critical region near the antiferromagnet transition. The authors use classical annealing simulations to argue that out-of-plane interactions and lattice defects can explain the emergence of such in-plane order and sample-dependent plateaus.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The in-plane 'new phase' rests on a single temperature point at one field; without a resolution check and scans across the C-window boundaries, a distinct thermodynamic phase is not fully established.","rationale":"I reviewed the strongest claim as the experimental discovery of a new in-plane ordered phase in HoB4 at B=1.8 T inside the C window. The most load-bearing condition for that claim is not the classical annealing model; the authors openly state that the model does not reproduce the observed 0.43 or 1/3 orders and call for quantum treatments. The load-bearing condition is instead that the observed satellite peaks constitute a distinct long-range-ordered phase. The paper presents only a narrow temperature scan at a single field, and CORELLI, while capable of elastic diffuse scattering, does not by itself separate a resolution-limited Bragg peak from rounded critical scattering. My proposed test will settle this directly. The fit inconsistency for gamma versus 1/7 (0.142±0.00025 vs 0.142857) is a real but secondary issue, since the new in-plane order would remain interesting even if incommensurate. I therefore leave the reader's CONDITIONAL verdict unchanged, with the condition shifted to the experimental peak-to-phase inference.","tokens_in":12554,"tokens_out":8599,"duration_ms":85249,"concrete_test":"Measure the temperature dependence of the [−2,1±gamma,0.43] and [−2,1±epsilon,0.43] peaks at B=1.8 T on a high-resolution neutron spectrometer (triple-axis with collimation or backscattering) from T=3 K to 8 K, and repeat the scan at B=1.5 T and B=2.1 T. If the satellite widths remain at the instrumental resolution below T_N2, broaden smoothly above T_N1, and the peaks are absent outside the susceptibility-defined C window, the phase assignment is supported. If the widths are broad at all temperatures or the peaks appear outside the C window, the 'new phase' should be downgraded to critical scattering or a sample-dependent artifact.","verdict_should_be":"UNCHANGED","load_bearing_attack":"In Section IV, the in-plane gamma and epsilon satellites are reported from CORELLI data at B=1.8 T, with gamma peaks present at T=5 K but absent at 4.65 K (Fig. 4c,f). The central claim that this is a new thermodynamic phase confined to the critical C window depends on two unverified assumptions: (1) the satellites are resolution-limited Bragg peaks rather than critical diffuse scattering or a multi-domain signature of the existing L_inc=0.43 order, and (2) the phase boundaries inferred from bulk susceptibility correctly identify the region where the satellites exist. No neutron scan is shown above T_N1 or at another field to verify confinement. The paper itself acknowledges that the annealing model 'fails to reproduce the L_inc=0.43 or the 1/3rd phase' and that 'more work is required to find either the 1/7th in-plane split peaks or the 1/3rd out-of-plane peaks' (Section V), so the presence of the peaks is the only direct evidence for the central claim. If the peaks are broad or persist outside the C window, the discovery is reclassified as critical scattering, not a phase.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript reports a combined neutron diffraction, magnetization/susceptibility, and simulated-annealing study of the Shastry-Sutherland candidate HoB4, using a single crystal for all measurements. The central experimental claim is the discovery of a previously unreported in-plane ordered phase confined to a critical temperature window between T_N1 and T_N2 at B = 1.8 T. In this window, neutron data show magnetic Bragg reflections with in-plane modulation vectors Q_eps = (±eps, 0, delta') and Q_gamma = (0, ±gamma, delta'), with reported eps = 0.0245 ± 0.004 r.l.u., delta' = 0.43 r.l.u., and gamma = 0.142 ± 0.00025 r.l.u., interpreted as a likely commensurate 1/7 in-plane ordering. The authors also present a 3D classical Ising SSL model with out-of-plane interactions and defects, showing that out-of-plane couplings can split in-plane Bragg peaks into multiple features and that defects can stabilize additional magnetization plateaus, offering a qualitative explanation for sample-dependent behavior. The paper concludes that defects and out-of-plane interactions are important for understanding frustrated SSL magnets, while acknowledging that the model does not reproduce the observed L_inc = 0.43 or 1/3 orders and that a full quantum treatment is beyond the manuscript's scope.","tokens_in":12874,"tokens_out":3032,"duration_ms":30777,"significance":"If the central claim is correct, the manuscript reports a genuinely new magnetic phase in HoB4: the only in-plane ordered phase identified in this compound, occurring in the critical regime between two established transitions. This would be a useful contribution to the experimental phase diagram of rare-earth Shastry-Sutherland magnets and would motivate further study of sub-leading Hamiltonian terms near phase boundaries. The experimental strengths include the use of a single crystal for all measurements, which removes sample-shape and demagnetization ambiguities, and the clear observation of an in-plane peak-splitting phenomenon that is not present in earlier reports. The simulation part, while explicitly acknowledged as qualitative, demonstrates a plausible mechanism by which out-of-plane interactions can generate in-plane structure in a frustrated Ising system, and the defect study provides a concrete and falsifiable suggestion for sample-dependent plateau formation. The paper is honest about the model's failures, which is a positive feature.","major_comments":[{"comment":"The assignment gamma = 0.142 ± 0.00025 approx 1/7 is not supported by the quoted uncertainty. The difference between 0.142 and 1/7 = 0.142857 is approximately 0.000857, which is about 3.4 standard deviations of the reported fitted value. Either the uncertainty is underestimated, the fit should be re-evaluated, or the modulation should be described as incommensurate with gamma approx 0.142. Since the phrase 'likely commensurate 1/7th ordering' is central to the characterization of the new phase, this point must be addressed before publication.","section":"Section IV, Fig. 4f"},{"comment":"The existence of a distinct thermodynamic phase in the critical C window currently rests on neutron data at a single temperature (T = 5 K) and a single field (B = 1.8 T). No scans are shown above T_N1 or at other field values to establish that the gamma satellites appear only inside the C phase, and no resolution analysis (for example, comparing peak widths with nuclear Bragg peaks) is presented to exclude critical diffuse scattering or a multi-domain splitting of the L_inc = 0.43 order. A temperature sweep across both phase boundaries and a field sweep at fixed temperature, together with a resolution check, are needed to substantiate the claim that this is a true phase rather than a near-critical fluctuation effect.","section":"Section IV, Fig. 4a-c"},{"comment":"The simulation is offered as a qualitative explanation for the in-plane ordering, but it explicitly fails to reproduce the L_inc = 0.43 or 1/3 orders, and the coupling parameters are initialized from dipole-dipole estimates and then varied over ±60% without a fitting procedure tied to the experimentally observed Q-vectors. As presented, the connection between Fig. 5(d-f) and the measured eps and gamma splittings is only qualitative. The mechanistic claim that out-of-plane interactions 'trigger' the observed in-plane order would be considerably strengthened by a quantitative comparison between the simulated splitting in Fourier space and the measured modulation vectors, or by identifying parameter regimes where the model reproduces the 0.43 and 1/7 peaks simultaneously.","section":"Section V, Eq. (2) and Fig. 5"},{"comment":"The model used is a longitudinal-field Ising model, but the authors note that the AFM phase has spins canted 23 degrees away from the c axis, meaning the field along c has a sizeable transverse component. The manuscript acknowledges that a transverse-field Ising model or quantum treatment may be required, but this limitation is important because the proposed classical annealing mechanism for the in-plane peaks could be invalid if transverse components or quantum fluctuations are the actual origin of the observed order. The authors should either test whether a small transverse-field term changes the annealing results, or explicitly restrict their mechanistic claim to the longitudinal-field component of the phase diagram.","section":"Section V, paragraph beginning 'Questions can arise'"}],"minor_comments":[{"comment":"The caption reports gamma = 0.14 r.l.u. while the main text reports gamma = 0.142 ± 0.00025 r.l.u.; these values should be made consistent.","section":"Fig. 4 caption and text"},{"comment":"The sign convention for the Zeeman term -h sum S_m should be stated explicitly, since the direction of the applied field relative to the Ising axis and the sign of h determine the physical meaning of positive and negative magnetization plateaus.","section":"Eq. (2)"},{"comment":"The interaction parameters in Table 2 are listed without units; it would be helpful to state explicitly that they are in units of J1 (or Kelvin/meV) in the table caption or in the text.","section":"Table 2"},{"comment":"Reference [10] duplicates reference [4] (both are Shastry and Sutherland, Physica B+C 108, 1069 (1981)); please replace one with another relevant citation.","section":"References"},{"comment":"The abstract contains a typo ('crystalize'); there are also minor grammatical issues in the introduction (for example, 'the spin s are arranged') that should be corrected in a careful proofreading pass.","section":"Abstract and Section I"}],"recommendation":"major_revision","confidential_remarks":"The central experimental observation is interesting and potentially significant, but the evidence for a distinct thermodynamic phase is currently based on a very limited set of neutron measurements. The commensurability issue with gamma requires either a correction or a revised interpretation. The simulation section is appropriately cautious, but it does not yet provide quantitative support for the mechanism. I would encourage the authors to provide the additional neutron data and analysis described in the major comments; with those additions, the paper could become a strong contribution to the field."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Quick take: the experimental centerpiece — a previously unseen in-plane modulation of the 0.43 order inside the critical C window of HoB4 — looks real and is worth taking seriously. The paper does not, however, establish that this corresponds to a 1/7 commensurate ordering, and the simulation part is qualitative at best.\n\nWhat is new: neutron CORELLI data on a single crystal show that at B=1.8 T, when heating from 3.5 K to 5 K, the incommensurate L=0.43 order develops extra in-plane satellites at (±ε,0,δ′) and then at (0,±γ,δ′) with γ≈0.142. That is not in earlier HoB4 literature. Using one crystal for susceptibility and neutron data is a real strength, and the phase diagram from susceptibility is carefully drawn.\n\nSoft spots. First, the 1/7 assignment: the quoted fit gives γ=0.142±0.00025, which is about 3.4σ away from 1/7. That is not a measurement of 1/7; the data are consistent with some incommensurate wave number near 1/7, not a pinned commensurate value. The authors say \"likely commensurate\" but the data do not support that. Easy fix: report the measured value and drop the 1/7 claim unless new data narrow it.\n\nSecond, the phase claim rests on essentially one temperature point. The γ satellites appear at 5 K and are absent at 4.65 K at 1.8 T. No scan above T_N1 or at another field is shown, so the confinement to the C window is inferred from bulk susceptibility, not checked by neutron. No resolution or linewidth analysis is presented, so critical diffuse scattering cannot be ruled out. \"New thermodynamic phase\" is not fully established; \"new elastic signal in the critical regime\" is.\n\nThird, the simulations do not explain the experimental discovery. The classical 3D Ising model with dipole-motivated couplings reproduces the qualitative splitting of in-plane peaks with increasing J7, but it explicitly fails to produce the 1/3 or 0.43 orders. That is a big gap. No code or data is shipped, so reproducibility is limited.\n\nVerdict: worth refereeing, but it needs revision. Fix the 1/7 statistics, add at least one more temperature and field point for the γ satellites, and check the peak widths. The core observation is likely to survive; the interpretation needs tightening.","headline":"The new in-plane scattering signal in HoB4's critical phase is worth taking seriously, but the 1/7 claim is statistically shaky and the phase claim needs more data.","tokens_in":13456,"tokens_out":2226,"would_cite":false,"duration_ms":21443,"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 reports the discovery of a previously unseen in-plane 1/7 magnetic order in HoB4 that exists only inside a narrow critical temperature window at 1.8 T.","keywords":["holmium tetraboride","Shastry-Sutherland lattice","frustrated magnetism","neutron diffraction","magnetization plateau","incommensurate magnetic order","Ising model","simulated annealing"],"falsifier":"Cool the same crystal through the lower transition at $B = 1.8$ T in fine temperature steps while tracking the $1/7$ satellite: if the order is intrinsic to the critical phase, the peak should vanish abruptly at the transition and reappear reversibly on warming, whereas hysteresis or a smeared onset would point to defect or domain-wall stabilization.","tokens_in":12385,"feed_emoji":"🧲","tokens_out":8866,"duration_ms":74292,"temperature":0.7,"pith_summary":"This paper argues that holmium tetraboride, a frustrated Shastry-Sutherland magnet, hosts a previously unseen magnetic phase at the edge of its antiferromagnetic order. In a narrow temperature window between $T_{N1}$ and $T_{N2}$ at $B = 1.8$ T, neutron scattering shows the out-of-plane incommensurate order acquiring an additional in-plane modulation, most clearly at a wave vector near $1/7$ of a reciprocal lattice unit. If the claim holds, the critical region between the two ordering temperatures contains a genuine ordered phase with in-plane components, distinct from the surrounding antiferromagnetic and paramagnetic phases. The paper also uses simulations of a three-dimensional longitudinal-field Ising model to show that out-of-plane couplings and lattice defects can split in-plane magnetic peaks and stabilize extra magnetization plateaus, offering a mechanism for sample-dependent features.","feed_headline":"New in-plane 1/7 magnetic order found in HoB4's critical phase","feed_subtitle":"Neutron data place the only in-plane order of holmium tetraboride between its two magnetic transitions at 1.8 T.","key_machinery":"The load-bearing mechanism is the three-dimensional Ising Shastry-Sutherland Hamiltonian extended with five in-plane couplings $J_1$--$J_5$, three out-of-plane couplings $J_6$--$J_8$, and a longitudinal Zeeman field $h$ (Eq. 2). Ground states are found by simulated annealing with parallel tempering on a $60 \\times 60 \\times 9$ spin lattice, and the resulting order is read from the Fourier transform of the two-spin correlation function (Eq. 4). The qualitative argument is that increasing the out-of-plane coupling $J_7$ splits a single in-plane ordering peak into pairs and quadruplets of peaklets, matching the neutron peak splitting in the critical phase, while single-site and 'chunk' defects generate narrow magnetization plateaus that are absent in the clean lattice.","core_discovery":"The central discovery is a new magnetic phase, the only one known in HoB4 with in-plane magnetic Bragg reflections, confined to the critical phase between $T_{N1} = 7.22$ K and $T_{N2} = 5.97$ K at $B = 1.8$ T. On warming from the antiferromagnetic phase, the incommensurate order at $L \\approx 0.43$ r.l.u. develops satellite peaks $\\vec{Q}_{\\varepsilon} = (\\pm\\epsilon,0,\\delta')$ and $\\vec{Q}_{\\gamma} = (0,\\pm\\gamma,\\delta')$, with $\\epsilon = 0.0245 \\pm 0.004$ r.l.u. and $\\gamma = 0.142 \\pm 0.00025 \\approx 1/7$ r.l.u. The authors describe the $1/7$ feature as a likely commensurate ordering that appears as an additional modulation of the out-of-plane incommensurate order; no other in-plane order is observed elsewhere in the phase diagram.","pith_inferences":["If the $1/7$ wave vector is a commensurate lock-in selected by sub-leading couplings, fine field sweeps near $T = 5$ K should reveal neighboring commensurate modulations (for example $1/9$ or $1/5$) at slightly different fields; the current data do not test this.","The coexistence of the out-of-plane incommensurate order with an in-plane modulation points toward a multi-$\\vec{Q}$ state; polarized neutron scattering could determine whether the combined order has a chiral or stripe character invisible in unpolarized Laue data.","The defect mechanism predicts a direct materials test: introducing controlled vacancies or stacking faults into HoB4 should create the same narrow magnetization plateaus at the fields where the simulations show them, while a deliberately defect-free crystal should lose the $5/9$ trace."],"forward_implications":["HoB4's critical temperature window should be treated as a distinct ordered phase, not a fluctuation-dominated crossover, and any future field-temperature phase diagram should include the in-plane-ordered $C$ phase at $B \\approx 1.8$ T between $T_{N1}$ and $T_{N2}$.","The robust out-of-plane incommensurate order at $L \\approx 0.43$ r.l.u. persists even as the $1/3$ plateau disappears, indicating it is set by leading Hamiltonian terms while the $1/3$ and $1/7$ orders are sub-leading.","Defect-induced plateaus can appear in narrow field ranges, so reported plateaus such as $1/2$, $4/9$, or $3/5$ may vary from sample to sample; the cleaner single crystal studied here shows only a trace near $5/9$.","Out-of-plane couplings alone can produce in-plane magnetic ordering in a Shastry-Sutherland magnet, so two-dimensional treatments are insufficient for HoB4 and a full three-dimensional model is required.","The absence of many small plateaus in this crystal suggests it has fewer defects than earlier samples, making it a useful reference for separating intrinsic from defect-driven physics."],"supporting_citations":[{"why":"Prior neutron and magnetization study of HoB4 that reported the 1/3 and 0.43 orders and the additional plateaus this paper re-examines; it is the baseline phase diagram the new phase is placed against.","marker":"[32]"},{"why":"Reports in-plane magnetic order in another rare-earth Shastry-Sutherland candidate, motivating the search for in-plane peaks in HoB4.","marker":"[14]"},{"why":"Provides the earlier collinear out-of-plane interpretation of rare-earth tetraboride plateaus that the discovery of in-plane order extends.","marker":"[15]"},{"why":"Exact ground-state analysis of the two-dimensional Ising Shastry-Sutherland model that anchors the simulated-annealing identification of magnetization plateaus.","marker":"[33]"},{"why":"Extends the Ising Shastry-Sutherland model with additional in-plane interactions, yielding new plateaus and in-plane order used as a starting point for the simulations.","marker":"[34]"},{"why":"Parallel-tempering study of an expanded Shastry-Sutherland Ising Hamiltonian that produced an in-plane 5/9 plateau, connecting to the 5/9 trace observed in this crystal.","marker":"[39]"}],"fun_headline_variants":["HoB4's critical phase hosts its sole in-plane 1/7 order","1/7 in-plane order emerges in HoB4's critical magnetic phase","HoB4 reveals unique in-plane modulation in critical regime","Only in-plane order in HoB4 appears at 1/7 in critical phase"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The simulation-based explanation assumes that a classical Ising model with the field along the $c$ axis describes the critical phase, even though the magnetic moments in the adjacent antiferromagnetic phase are canted $23^\\circ$ away from $c$, leaving a sizeable transverse field component.","fun_headline_variants_meta":{"raw":{"variants":["HoB4's critical phase hosts its sole in-plane 1/7 order","1/7 in-plane order emerges in HoB4's critical magnetic phase","HoB4 reveals unique in-plane modulation in critical regime","Only in-plane order in HoB4 appears at 1/7 in critical phase"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000209,"raw_usage":{"total_tokens":1423,"prompt_tokens":979,"completion_tokens":444,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":595,"completion_tokens_details":{"reasoning_tokens":362}},"tokens_in":595,"tokens_out":444,"duration_ms":4370,"temperature":1.0,"reasoning_tokens":362,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-16T11:13:43.807425+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Cool the same crystal through the lower transition at $B = 1.8$ T in fine temperature steps while tracking the $1/7$ satellite: if the order is intrinsic to the critical phase, the peak should vanish abruptly at the transition and reappear reversibly on warming, whereas hysteresis or a smeared onset would point to defect or domain-wall stabilization.","supporting_citations":[{"cited_title":"Onizuka et al., Journal of the Physical Society of Japan 69, 1016-1018 (2000)","cited_arxiv_id":null,"evidence_quote":"Prior neutron and magnetization study of HoB4 that reported the 1/3 and 0.43 orders and the additional plateaus this paper re-examines; it is the baseline phase diagram the new phase is placed against."},{"cited_title":"Jensen and A","cited_arxiv_id":null,"evidence_quote":"Reports in-plane magnetic order in another rare-earth Shastry-Sutherland candidate, motivating the search for in-plane peaks in HoB4."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Provides the earlier collinear out-of-plane interpretation of rare-earth tetraboride plateaus that the discovery of in-plane order extends."},{"cited_title":"Shi et al., Nat","cited_arxiv_id":null,"evidence_quote":"Exact ground-state analysis of the two-dimensional Ising Shastry-Sutherland model that anchors the simulated-annealing identification of magnetization plateaus."},{"cited_title":"Matsuda et al., Phys","cited_arxiv_id":null,"evidence_quote":"Extends the Ising Shastry-Sutherland model with additional in-plane interactions, yielding new plateaus and in-plane order used as a starting point for the simulations."},{"cited_title":"Haravifard et al., PNAS","cited_arxiv_id":null,"evidence_quote":"Parallel-tempering study of an expanded Shastry-Sutherland Ising Hamiltonian that produced an in-plane 5/9 plateau, connecting to the 5/9 trace observed in this crystal."}],"review_version":1}