{"id":"2eb5b522-524b-4b4e-b1b3-5c00de813d5e","arxiv_id":"2607.03712","paper_version":1,"verdict":"CONDITIONAL","confidence":"HIGH","novelty_score":4.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":4,"one_line_summary":"Isovalent Sb substitution in PrFeAs1-xSbxO0.7F0.3 yields a crossover from modest electronic tuning of Tc (~48→44 K for x≤0.3) to disorder-driven suppression, with enhanced Hc2 and vortex pinning but low Jc from poor grain connectivity.","lead":"Substituting antimony for arsenic in fluorine-doped PrFeAs(O,F) slowly lowers the superconducting transition from about 48 K to 44 K up to 30% Sb, then collapses it as disorder and secondary phases take over. The work maps how isovalent lattice expansion and non-magnetic disorder trade off against vortex pinning in a rare-earth 1111 iron pnictide.","discovery_kind":"extension","skeptic_critique":{"model":"grok-4.5","headline":"No significant objection identified beyond the reader's secondary-phase caveat; the multi-probe trends still support the claimed crossover.","rationale":"The reader's strongest claim accurately restates the abstract and Discussion (Fig. 7 and concluding paragraphs): gradual Tc drop and improved local pinning/Hc2 for x≤0.3, then rapid collapse with rising ρ0, falling RRR, and secondary-phase growth for 0.3<x≤0.6. The weakest assumption correctly flags the secondary-phase network as the main interpretive risk. After re-reading Structural Analysis, Raman/DFT, magnetotransport (Figs. 4–5), magnetic data (Fig. 6), and the Discussion, I find no stronger load-bearing flaw. Lattice expansion, phonon softening, and the coincidence of residual-resistivity rise with the Tc cliff supply independent evidence that lattice-incorporated Sb is doing real work up to x~0.3; secondary phases are already invoked by the authors to explain low Jc and high-x failure. Single-band WHH on a multiband material and limited data sharing are acknowledged limitations but do not invert the crossover narrative. Therefore the CONDITIONAL verdict stands; no adjustment is required.","tokens_in":19578,"tokens_out":711,"duration_ms":6298,"concrete_test":"Re-refine all XRD patterns with full multiphase Rietveld (main 1111 + Fe/FeSb/FeSb2 + Pr2SbO2 + PrOF) and plot Tc, ΔT, ρ0, U0(H), and Hc2 slope versus both nominal x and refined 1111-phase fraction / actual Sb occupancy of the pnictogen site (from EDX or site-occupancy refinement). If the weak-suppression/enhanced-pinning regime (x≤0.3) survives when plotted against actual lattice Sb content and remains present only while secondary-phase fraction stays low, the crossover claim is reinforced; if the trends collapse once secondary-phase fraction is controlled for, the electronic-tuning interpretation weakens.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The reader's weakest assumption is already the central interpretive limit: whether trends for x≤0.6 primarily track lattice-incorporated Sb (lattice expansion, phonon softening, non-magnetic disorder) rather than the secondary-phase network that reaches ~26% Fe–Sb binaries at x=0.6 (Structural Analysis; Supp. Table ST1). That concern is real but does not overturn the strongest claim. XRD/EDX show systematic c-axis and volume expansion plus actual Sb content tracking nominal x up to ~0.6; Raman shows progressive A1g pnictogen-mode softening that DFT attributes to mass+size effects of Sb on the FePn layer; residual resistivity and RRR degrade sharply only above x~0.3, coinciding with the rapid Tc drop. These lattice- and phonon-level signatures cannot be produced by secondary phases alone. The paper itself already attributes the low Jc and high-x collapse to intergranular secondary phases while locating the moderate-x Hc2/U0 gains in Sb-induced disorder. Thus the electronic-tuning \to disorder-crossover narrative remains the most economical reading of the multi-probe data; secondary-phase quantification is a refinement, not a load-bearing contradiction.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.5","summary":"The manuscript reports a multi-probe study of isovalent Sb substitution on the As site in optimally F-doped polycrystalline PrFeAs1-xSbxO0.7F0.3 (x = 0–1.0). XRD/Rietveld and EDX show progressive c-axis and volume expansion with Sb incorporation up to x ≈ 0.6, after which secondary phases (Fe–Sb binaries, Pr–Sb–O) dominate. Raman spectra and DFT phonon calculations document systematic softening of the pnictogen A1g mode. Transport shows a gradual Tc drop from ~48 K to ~44 K for x ≤ 0.3, then rapid suppression to ~28 K at x = 0.6, accompanied by rising residual resistivity and falling RRR. Magnetotransport (to 9 T) yields enhanced dHc2/dT and WHH-estimated Hc2(0) (~350 T at x = 0.30) plus higher TAFF activation energies U0, while Bean-model Jc remains low (~10² A cm⁻²). The authors interpret the data as a crossover from electronically tuned superconductivity at moderate Sb content to a disorder- and secondary-phase-dominated regime at higher x.","tokens_in":19896,"tokens_out":1140,"duration_ms":8825,"significance":"Isovalent pnictogen substitution is comparatively under-explored in the 1111 family relative to Ba-122 and FeSe. The work supplies a coherent multi-technique data set (structure, Raman+DFT, zero-field and field-dependent transport, TAFF, magnetization, Jc) on a magnetically active rare-earth 1111 system and places the results against prior Sb-doped Sm-1111 and P-doped 1111 literature. The reported moderate-x enhancement of Hc2 and U0, together with the documented lattice-expansion/phonon-softening signatures, is a useful addition to the phenomenology of non-magnetic disorder in iron pnictides. The central claim is experimentally grounded and of interest to the IBS community, even though polycrystalline connectivity limits the absolute Jc values.","major_comments":[{"comment":"Structural Analysis and Supplementary Table ST1: at x = 0.6 the FeSb/FeSb2 fraction already reaches ~26%. The electronic-tuning vs disorder-crossover narrative for 0.3 < x ≤ 0.6 therefore rests on the assumption that lattice-incorporated Sb (not the secondary-phase network) still controls the measured Tc, ρ0, and U0 trends. The paper should quantify more explicitly how much of the rapid Tc collapse and residual-resistivity rise can be attributed to percolative disruption by secondary phases versus intrinsic pair-breaking from Sb on the FeAs lattice (e.g., by correlating phase fractions with ρ0 and ΔT across the full series, or by discussing grain-boundary vs intragrain contributions more quantitatively).","section":null},{"comment":"Magnetotransport / WHH analysis (text around Fig. 4): Hc2(0) is obtained from the single-band WHH formula Hc2(0) = −0.693 Tc (dHc2/dT)|Tc, yielding ~350 T at x = 0.30. The manuscript itself notes multiband character and a large Maki parameter, so the absolute Hc2(0) values are upper-bound estimates. The claim of “enhanced upper critical fields (~200–350 T)” should be framed more carefully as an enhancement of the measured slope (and of the orbital-limiting scale) rather than as a robust zero-temperature Hc2, or a two-band estimate should be provided for at least one composition.","section":null}],"minor_comments":[{"comment":"Figure captions and text inconsistently write the stoichiometry as PrFeAs1-xSbxF0.7O0.3 or PrFeAs1-xSbxO0.7F0.3; standardize to one form throughout.","section":null},{"comment":"Figure 2 caption refers to “PrFe1-xSxAsO0.7F0.3” (S instead of Sb); correct the typo.","section":null},{"comment":"Several figure panels (e.g., Fig. 3, Fig. 7) would benefit from explicit error bars on Tc, ΔT, and ρ0 extracted from the fits.","section":null},{"comment":"The DFT phonon comparison (inset of Fig. 2) is only for the end-member PrFeAsO vs hypothetical PrFeSbO; a brief statement of the computational settings (code, functional, k-mesh) would improve reproducibility.","section":null},{"comment":"References to the authors’ own prior PrFeAs(O,F) and Mn-doped work are appropriate for baselines, but a short explicit comparison of absolute Jc and U0 values with those earlier samples would help the reader gauge the magnitude of the Sb effect.","section":null}],"recommendation":"minor_revision","confidential_remarks":"The secondary-phase caveat is real but already partially acknowledged by the authors; it does not overturn the multi-probe trends. The manuscript is a solid experimental contribution suitable for a specialized superconductivity or condensed-matter journal after the two major points are tightened. No novelty or citation-pattern concerns."},"author_rebuttal":null,"desk_editor":{"model":"grok-4.5","letter":"This is the first systematic Sb-for-As series in optimally F-doped PrFeAsO0.7F0.3. It is not a pairing-mechanism breakthrough and it closely parallels the same group’s Sm-1111 Sb work, but it is a clean, multi-probe materials map that the 1111 community will actually use.\n\nWhat they did well: XRD/Rietveld plus EDX show lattice expansion and actual Sb tracking nominal x up to ~0.6; Raman plus DFT phonon frequencies give a clear mass+size softening of the pnictogen A1g mode; zero-field and 9 T transport, TAFF Arrhenius fits, ZFC/FC, and Bean Jc all line up on the same story—Tc only weakly down from ~48 K to ~44 K for x≤0.3 with higher Hc2 slopes and higher U0, then rapid collapse, rising ρ0, falling RRR, and secondary-phase growth for 0.3<x≤0.6. The crossover framing is earned by the data, not imposed on it. Self-citations to their own Pr and Mn baselines are appropriate.\n\nSoft spots, in proportion: polycrystalline samples with secondary phases (Fe–Sb binaries already ~26% at x=0.6) mean the low Jc and high-x collapse are partly intergranular, which the paper itself states. Single-band WHH on a multiband material is the usual over-estimate of Hc2(0); they flag the multiband caveat. Data are not shared. None of these overturn the central claim—the lattice expansion, phonon softening, and the sharp change in residual scattering above x~0.3 cannot be produced by secondary phases alone.\n\nWho it is for: people working on 1111 doping, vortex pinning, or isovalent pnictogen substitution. It deserves a serious referee. I would accept it for peer review and would cite the Pr-series numbers and the crossover summary when I next write about 1111 disorder or pinning.","headline":"Solid first systematic Sb-for-As map in optimally F-doped Pr-1111; multi-probe data support a real electronic-tuning-to-disorder crossover, with secondary phases as a known limit rather than a fatal flaw.","tokens_in":20601,"tokens_out":520,"would_cite":true,"duration_ms":5802,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.5","headline":"Isovalent Sb at the As site in optimally F-doped PrFeAs(O,F) first tunes superconductivity gently, then disorder takes over and collapses it.","keywords":["iron-based superconductors","1111 family","isovalent substitution","antimony doping","upper critical field","vortex pinning","critical current density","PrFeAs(O,F)"],"falsifier":"A single-crystal or carefully purified polycrystalline series in which EDX and Rietveld show negligible Fe–Sb or Pr–Sb–O secondary phases yet still exhibit the same rapid Tc collapse and ρ0 rise above x = 0.3 would confirm lattice-incorporated disorder as the cause; the opposite result would falsify the electronic-tuning-to-disorder narrative.","tokens_in":20493,"feed_emoji":"❄️","tokens_out":734,"duration_ms":5817,"temperature":0.7,"pith_summary":"The paper maps how replacing arsenic with isovalent antimony in optimally fluorine-doped PrFeAsO0.7F0.3 changes superconductivity without adding or removing charge. At low Sb levels (x ≤ 0.3) the superconducting transition falls only from about 48 K to about 44 K, the lattice expands, pnictogen phonon modes soften, upper critical fields rise, and the energy barrier for vortex motion increases, so pinning improves while superconductivity stays relatively robust. Beyond that window, residual resistivity climbs, secondary phases proliferate, the transition broadens and collapses, and bulk superconductivity is lost. The work therefore shows a concrete crossover: moderate isovalent substitution can still tune the electronic and vortex landscape of a 1111 iron pnictide, but further substitution hands control to disorder and phase segregation. A reader who cares about how to engineer high-Tc iron pnictides without carrier doping can treat the x ≈ 0.3 boundary as an empirical limit for useful Sb incorporation.","feed_headline":"Sb tunes PrFeAs(O,F) gently, then disorder kills Tc","feed_subtitle":"Below x=0.3 superconductivity holds and pinning improves; above it, secondary phases and scattering take over","key_machinery":"The compositional crossover near x ≈ 0.3, diagnosed by the simultaneous evolution of lattice parameter c, pnictogen A1g Raman mode, residual resistivity ρ0, RRR, Hc2 slope and vortex activation energy U0(H).","core_discovery":"In optimally F-doped PrFeAs1-xSbxO0.7F0.3, isovalent Sb substitution produces a clear crossover: for x ≤ 0.3 superconductivity is only weakly suppressed (Tc from ~48 K to ~44 K) while lattice expansion, phonon softening, higher Hc2 and higher vortex activation energy appear; for 0.3 < x ≤ 0.6 disorder and secondary phases dominate and Tc falls rapidly.","pith_inferences":[],"forward_implications":[],"fun_headline_variants":["Sb expands lattice softens modes lifts pinning until disorder kills Tc","Moderate Sb holds Tc near 44K boosts Hc2 and vortex pinning","Crossover at x=0.3: electronic tuning yields to disorder in PrFeAs","Isovalent Sb: mild Tc drop then secondary phases crush superconductivity","Higher activation energy for x≤0.3 Sb then rapid Tc fall dominates"],"cache_read_input_tokens":16512,"weakest_assumption_plain":"The measured trends up to x = 0.6 mainly reflect Sb that has entered the FeAs lattice rather than the growing network of secondary phases that already reaches roughly a quarter of the sample at higher doping.","fun_headline_variants_meta":{"raw":{"variants":["Sb expands lattice softens modes lifts pinning until disorder kills Tc","Moderate Sb holds Tc near 44K boosts Hc2 and vortex pinning","Crossover at x=0.3: electronic tuning yields to disorder in PrFeAs","Isovalent Sb: mild Tc drop then secondary phases crush superconductivity","Higher activation energy for x≤0.3 Sb then rapid Tc fall dominates"]},"model":"grok-4.5","effort":"low","cost_usd":0.006898,"raw_usage":{"total_tokens":1717,"prompt_tokens":755,"num_sources_used":0,"completion_tokens":82,"cost_in_usd_ticks":68980000,"prompt_tokens_details":{"text_tokens":755,"audio_tokens":0,"image_tokens":0,"cached_tokens":256},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":880,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":755,"tokens_out":82,"duration_ms":6749,"temperature":1.0,"reasoning_tokens":880,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-07-12T00:27:54.368061+00:00","model_set":{"reader":"grok-4.5"},"falsifier":"A single-crystal or carefully purified polycrystalline series in which EDX and Rietveld show negligible Fe–Sb or Pr–Sb–O secondary phases yet still exhibit the same rapid Tc collapse and ρ0 rise above x = 0.3 would confirm lattice-incorporated disorder as the cause; the opposite result would falsify the electronic-tuning-to-disorder narrative.","supporting_citations":[],"review_version":1}