{"id":"6278dbe8-4a15-4152-85cd-fea71880e0e0","arxiv_id":"1908.05973","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":4,"one_line_summary":"Pr2-xSrxMgIrO6 (x = 0, 0.5, 1) are all insulating, SOC-driven iridates with no half-metallic antiferromagnetism, and Pr3+ acts only as a paramagnetic background.","lead":"The authors synthesized three iridate double perovskite compounds and measured their structure, transport, and magnetism. They show the doped compounds are insulators, not the predicted half-metallic antiferromagnets, and that magnetism comes from iridium moments.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The Ir-only magnetism claim depends on the untested assumption that Pr3+ stays a nonmagnetic singlet; a small ordered Pr moment at the 14 K or 6 K transitions would break the moment balance.","rationale":"Read in good faith, the paper's headline contribution is an experimental refutation of HMAFM in PrSrMgIrO6, supported by resistivity, valence-band XPS, and Arrott plots. That part is solid. The second major claim, that Pr3+ is a mere paramagnetic background and ordered magnetism is entirely Ir, is less secure. The reader identified exactly this as the weakest assumption, and I agree. I considered whether a stronger objection exists: the Curie–Weiss fits lack uncertainties, the PSMIO excess moment of 0.3 μB is comparable to typical fit error, and the 6 K kink in PSMIO1505 is very weak. These are all consequences of the same missing direct Pr-sublattice measurement. The paper's own Section IV states the Pr conclusion as established, but Section III F's argument is indirect. This is an unverified assumption rather than an internal contradiction, so it does not warrant rejection; it does warrant conditional acceptance with a request for a microscopic probe. Hence the reader's CONDITIONAL verdict stands unchanged.","tokens_in":17119,"tokens_out":4334,"duration_ms":44882,"concrete_test":"Collect neutron powder diffraction data on PMIO at T = 2, 10, and 20 K, and on PSMIO1505 at 2, 4, and 10 K. Refine the magnetic structure with independent Pr and Ir sublattice moments. If a Pr moment ≥ 0.1 μB is required by the magnetic Bragg intensities, or if the ordered moment sum exceeds the Ir-only expectation from isostructural La2MgIrO6, the Ir-only ordering claim is falsified; if Pr refines to zero, the concern is resolved.","verdict_should_be":"UNCHANGED","load_bearing_attack":"Section III F builds the central assignment that all ordered magnetism comes from Ir on three supports: (a) the non-Kramers Pr3+ singlet argument with refs 39–42, (b) Curie–Weiss moment sums (Eqs. 1–5), and (c) the absence of susceptibility anomalies assignable to Pr. Neither (a) nor (b) is a direct probe of the Pr sublattice. The cited singlet behavior is demonstrated in other perovskite/double-perovskite A-sites, not in Pr2−xSrxMgIrO6; the local crystal field here is monoclinic and has not been measured for these compounds (no inelastic neutron scattering, Pr XAS, or specific heat). The moment balance uses the free-ion Pr3+ value 3.58 μB and a transferred LMIO Ir4+ moment, without error bars; the PSMIO excess of ~0.3 μB/f.u attributed to Ir5+ is within typical Curie–Weiss fit uncertainty. Bulk χ cannot distinguish a small ordered Pr moment from the dominant Ir/Pr paramagnetic background, especially if Pr orders at the same temperature as Ir. If Pr3+ carries even ~0.2–0.5 μB below 14 K in PMIO or couples to Ir moments in PSMIO1505, the AFM transition assignments and the 'Pr3+ only paramagnetic background' conclusion in Section IV would need revision. The HMAFM refutation itself (insulating transport, gapped valence band, no spontaneous moment) is not affected by this concern.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports a combined structural, spectroscopic, transport, and magnetization study of the double perovskites Pr2-xSrxMgIrO6 (x = 0, 0.5, 1). The authors find all three compounds to be insulating with no density of states at the Fermi level and no spontaneous ferromagnetic moment in the doped samples. XANES and XPS establish the Ir valence progression from 4+ to 5+. Magnetic measurements reveal an AFM transition near 14 K in Pr2MgIrO6, a weakened transition near 6 K in Pr1.5Sr0.5MgIrO6, and no ordering down to 2 K in PrSrMgIrO6. The central conclusions are that the predicted half-metallic antiferromagnetic state is absent, that the magnetic properties are governed by Ir moments, and that Pr3+ contributes only a paramagnetic background without ordering or coupling to Ir.","tokens_in":17473,"tokens_out":5672,"duration_ms":54044,"significance":"If the conclusions hold, the paper provides a convincing experimental refutation of the HMAFM proposal of Ghimire et al. for PrSrMgIrO6, supported by several independent probes: gapped transport, valence-band XPS, absence of spontaneous magnetization, and Arrott analysis. The systematic oxidation-state determination and careful XRD/EXAFS structural characterization are strengths, as is the qualitative high-resolution RIXS comparison with Ba2YIrO6. However, the claim that Pr3+ is magnetically inert is less secure, because it relies on an assumed nonmagnetic crystal-field singlet and an indirect moment balance rather than a direct probe of the Pr sublattice. This weakens the paper's strongly stated conclusion about the exclusive role of Ir moments.","major_comments":[{"comment":"The moment balance uses the free-ion Pr3+ effective moment of 3.58 μB and an Ir4+ moment taken from a separately measured LMIO sample, but no uncertainties are propagated through Eqs. (1)-(5). The numerical agreement with the Curie-Weiss effective moments is therefore not an independent quantitative verification of the Pr3+ paramagnetic-only assumption. The conclusion that Pr3+ neither orders nor couples to the Ir sublattice needs direct evidence (e.g., neutron diffraction, muon spin rotation, or Pr-resonant X-ray scattering) or at least an explicit caveat that bulk susceptibility cannot rule out a small ordered Pr moment below the AFM transitions.","section":"Section III F, Eqs. (1)-(5)"},{"comment":"The excess of ~0.3 μB/f.u. over the Pr3+ free-ion value is assigned to a finite Ir5+ moment, but this number is smaller than typical Curie-Weiss fitting uncertainties, and no error bars are supplied for the fit parameters or for the LMIO reference moment. The inference that a correlated moment develops on every Ir site is therefore not quantitatively established; the excess could equally arise from a deviation of the Pr3+ effective moment from the free-ion value in the crystal field. The authors should present error bars and a sensitivity analysis, or temper this conclusion.","section":"Section III F (PSMIO discussion)"},{"comment":"The absence of ZFC/FC divergence and the presence of only weak kinks in χ(T) are used to rule out ordering on the Pr sublattice, but bulk dc susceptibility has limited sensitivity to a small ordered Pr moment when a large Pr/Ir paramagnetic background is present. If Pr3+ carries even ~0.2-0.5 μB below 14 K in PMIO or couples to Ir moments in PSMIO1505, the assignment of the transitions purely to Ir moments would need revision. The authors should explicitly state this limitation or provide complementary specific-heat, neutron, or μSR data.","section":"Section III F and Figure 7"}],"minor_comments":[{"comment":"Reference 42 contains a corrupted author name: 'Jaworska-Go/suppress l¸ ab' should be corrected to the proper author string.","section":"References"},{"comment":"There are typographical errors such as 'infact' (Introduction) and 'valance band' (should be 'valence band' in several places); please proofread carefully.","section":"Introduction and throughout"},{"comment":"'Arrot plot' should be 'Arrott plot' in the text and figure caption.","section":"Section III F and Figure 7 caption"},{"comment":"The text refers to the ESRF beamline as 'ID23' when describing the PSMIO RIXS measurement, while the Experimental Section states ID20; please reconcile this discrepancy.","section":"Section III D"}],"recommendation":"major_revision","confidential_remarks":"The HMAFM refutation is well supported and valuable, but the paper's central claim about Pr3+ being magnetically inert is presented too strongly relative to the evidence. The authors could probably fix this within the manuscript's scope by adding direct magnetic characterization or by substantially softening the conclusion and clearly labeling the Pr scenario as an inference. I recommend major revision rather than rejection because the core negative result (no half-metallicity, no spontaneous moment) is robust."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Dear Colleague,\n\nThe headline: this paper does what it says – it refutes the HMAFM prediction for PrSrMgIrO6 with solid bulk measurements, and the insulating character of all three compounds is established beyond reasonable doubt. That alone makes it worth a careful read.\n\nWhat is new: it is the first experimental test of Ghimire et al.'s theory for this specific series. The doping series is well characterized structurally (XRD, EXAFS), electronically (resistivity, valence-band XPS, XANES, core-level XPS), and magnetically (susceptibility, Arrott plots). The RIXS comparison between PSMIO and Ba2YIrO6 is a nice addition; it shows the monoclinic distortions and altered hopping paths are enough to break the ideal J=0 picture. The paper is honest about the limits of the atomic-J description.\n\nThe soft spot is exactly what the stress-test note flags: the claim that Pr3+ never orders and only contributes a paramagnetic background is supported by inference, not a direct probe. The non-Kramers singlet argument cites other perovskites, but the local crystal field here is monoclinic and unmeasured for these compounds. The moment balance uses free-ion Pr3+ and a transferred LMIO Ir moment without error bars; the excess ~0.3 μB assigned to Ir5+ in PSMIO is within typical Curie-Weiss fit noise. If Pr3+ carried a small ordered moment at the 14 K or 6 K transitions, the AFM assignments and the moment balance would need revision. None of this touches the central refutation of half-metallicity, which stands on transport and XPS alone. But the paper's stronger statement – that the magnetism is entirely Ir-driven – goes beyond what the data can prove.\n\nWho this is for: anyone working on 5d double perovskites, iridates, or the J=0 vs. finite-moment debate. It is a useful data point, not a paradigm shift.\n\nMy recommendation: send it to peer review. A good referee should ask for uncertainty estimates on the Curie-Weiss moments and a more cautious framing of the Pr3+ conclusion, perhaps with a sentence saying that microscopic probes would be needed to confirm it. But the core result is solid and the paper deserves to be published after those revisions.","headline":"Solid experimental refutation of HMAFM in PrSrMgIrO6, with a softer-than-claimed Pr3+ non-ordering conclusion that needs a direct probe.","tokens_in":18022,"tokens_out":2008,"would_cite":true,"duration_ms":19223,"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":"In the double perovskites Pr2−xSrxMgIrO6, ordered magnetism comes from iridium while praseodymium stays paramagnetic, so the predicted half-metallic antiferromagnet does not form.","keywords":["iridate double perovskites","spin-orbit coupling","half-metallic antiferromagnetism","Pr3+ singlet","d4 iridium magnetism","antiferromagnetic order","RIXS","Mott insulator"],"falsifier":"Neutron diffraction or muon-spin rotation on Pr2MgIrO6 below 14 K would settle it: an ordered moment on the Pr site, or a second transition below 2 K in PrSrMgIrO6, would contradict the assignment of all ordered magnetism to iridium. Equally decisive would be spin-resolved photoemission showing a finite density of states at the Fermi level in either doped compound.","tokens_in":16948,"feed_emoji":"🧲","tokens_out":6438,"duration_ms":58026,"temperature":0.7,"pith_summary":"This paper sets out to test a theoretical prediction that strontium doping would turn the double perovskite Pr2MgIrO6 into a half-metallic antiferromagnet. Using magnetization, resistivity, X-ray absorption, photoemission, and RIXS on three compositions ($x = 0$, 0.5, 1), the authors conclude that no half-metallicity appears: every composition is an insulator whose gap is set by spin-orbit coupling on iridium. The ordered magnetic response likewise belongs to iridium, with Ir4+ moments ordering at 14 K, the transition weakening to about 6 K with doping, and no order at all for the Ir5+ compound, while Pr3+ contributes only a paramagnetic background. The result matters because it removes a candidate route to half-metallic antiferromagnetic spintronics and sharpens the picture of how 5d electrons and local crystal distortions compete.","feed_headline":"Iridium carries all ordered magnetism in three iridate double perovskites","feed_subtitle":"Magnetization and transport rule out half-metallic antiferromagnetism: all three compounds are spin-orbit insulators.","key_machinery":"The argument is carried by the spin-orbit-coupled $J$ multiplets of iridium, tuned by strontium doping from the magnetic $d^5$ configuration (Ir4+) to the nominally nonmagnetic $d^4$ configuration (Ir5+). The load-bearing comparison is with barium yttrium iridate, a cubic $d^4$ double perovskite whose low-energy RIXS features and small moments show that the ideal nonmagnetic $J = 0$ state is destabilized by octahedral tilting, noncubic crystal fields, and Ir-Ir hopping; the same mechanism is invoked for PrSrMgIrO6. The other pillar is the non-Kramer Pr3+ ion, whose low-symmetry crystal field leaves a singlet ground state, so it can only contribute a temperature-independent paramagnetic background rather than ordered moments.","core_discovery":"The central experimental finding is that none of the three double perovskites is half-metallic and none shows long-range magnetic order on the praseodymium sublattice. In Pr2MgIrO6 (Ir4+, $d^5$) the authors observe a sharp antiferromagnetic transition near 14 K; substituting strontium oxidizes iridium toward 5+ ($d^4$) and weakens the exchange, shifting the transition to about 6 K in Pr1.5Sr0.5MgIrO6 and suppressing order entirely in PrSrMgIrO6 down to 2 K. Curie-Weiss analysis, using La2MgIrO6 as a reference for the Ir4+ moment, reproduces the measured effective moments when Pr3+ is treated as a nonmagnetic singlet contributing only its paramagnetic susceptibility. The authors therefore conclude that the spin-orbit-coupled $J$ states of iridium control both the insulating gap and the correlated magnetism, and that the atomic $J = 0$ picture for Ir5+ fails because noncubic crystal fields and intersite hopping generate small moments.","pith_inferences":["Inference: measuring the same series with praseodymium replaced by a nonmagnetic rare earth (for example yttrium or lanthanum) would separate the iridium-only magnetism from any residual 4f contribution and test whether the small Ir5+ moment is intrinsic to the $d^4$ double perovskite.","Inference: because Pr3+ is claimed to be a singlet, a low-temperature specific-heat measurement should show only the iridium contribution plus the lattice; an extra Schottky anomaly from a praseodymium crystal-field doublet would indicate the singlet assumption needs revision.","Inference: the absence of order down to 2 K with a Curie-Weiss temperature near -39 K makes PrSrMgIrO6 a candidate for a frustrated, possibly spin-liquid-like state of weak Ir moments, but identifying the ground state would need muon spin rotation or neutron scattering."],"forward_implications":["If the measurements are right, the proposed transition from spin-orbit Mott insulator to half-metallic antiferromagnet does not occur in this series, so this family should be dropped from half-metallic antiferromagnet candidate lists.","The insulating behavior of all three compositions, including the $d^4$ end member, supports spin-orbit coupling as the gap-forming interaction even when the atomic $J = 0$ limit is broken.","Weakening of the antiferromagnetic order from 14 K to 6 K to no order tracks the dilution of magnetic Ir4+ by nonmagnetic Ir5+, implying exchange rather than single-ion physics sets the ordering temperature.","Pr3+ being inert means any future claim of Pr-Ir coupling in this family needs direct evidence such as an ordered moment on the praseodymium site."],"supporting_citations":[{"why":"The theoretical prediction of half-metallic antiferromagnetism in PrSrMgIrO6 that this paper's magnetic and transport data directly test and refute.","marker":"[16]"},{"why":"Provides the isostructural La2MgIrO6 reference used to isolate the Ir4+ effective moment in the Curie-Weiss analysis.","marker":"[18]"},{"why":"Supplies the cubic $d^4$ comparison compound Ba2YIrO6 and its RIXS data, used to argue that hopping and noncubic fields break the $J = 0$ state.","marker":"[10]"},{"why":"Argues that intersite hopping rescales atomic spin-orbit coupling in $d^4$ iridates, the mechanism the authors invoke for the small Ir5+ moment.","marker":"[15]"},{"why":"Documents singlet ground states of non-Kramer Pr3+ in perovskite-like crystal fields, supporting the claim that Pr3+ is paramagnetically inert.","marker":"[39–42]"}],"fun_headline_variants":["No half-metallic antiferromagnetism in iridate double perovskites","Ir moments order, Pr stays paramagnetic in three iridate perovskites","Strontium doping weakens Ir antiferromagnetism in Pr2-xSrxMgIrO6","Spin-orbit insulators: three iridates rule out half-metallic state","Ir antiferromagnetism weakens with Sr doping: 14 K to 6 K to none"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The claim that Pr3+ is magnetically inert rests on the assumption that Pr3+ has a nonmagnetic singlet ground state under the low-symmetry A-site crystal field, so it neither orders nor couples to iridium moments.","fun_headline_variants_meta":{"raw":{"variants":["No half-metallic antiferromagnetism in iridate double perovskites","Ir moments order, Pr stays paramagnetic in three iridate perovskites","Strontium doping weakens Ir antiferromagnetism in Pr2-xSrxMgIrO6","Spin-orbit insulators: three iridates rule out half-metallic state","Ir antiferromagnetism weakens with Sr doping: 14 K to 6 K to none"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000932,"raw_usage":{"total_tokens":4125,"prompt_tokens":1218,"completion_tokens":2907,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":834,"completion_tokens_details":{"reasoning_tokens":2794}},"tokens_in":834,"tokens_out":2907,"duration_ms":19328,"temperature":1.0,"reasoning_tokens":2794,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-14T12:58:44.439917+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Neutron diffraction or muon-spin rotation on Pr2MgIrO6 below 14 K would settle it: an ordered moment on the Pr site, or a second transition below 2 K in PrSrMgIrO6, would contradict the assignment of all ordered magnetism to iridium. Equally decisive would be spin-resolved photoemission showing a finite density of states at the Fermi level in either doped compound.","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"The theoretical prediction of half-metallic antiferromagnetism in PrSrMgIrO6 that this paper's magnetic and transport data directly test and refute."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Provides the isostructural La2MgIrO6 reference used to isolate the Ir4+ effective moment in the Curie-Weiss analysis."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Supplies the cubic $d^4$ comparison compound Ba2YIrO6 and its RIXS data, used to argue that hopping and noncubic fields break the $J = 0$ state."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Argues that intersite hopping rescales atomic spin-orbit coupling in $d^4$ iridates, the mechanism the authors invoke for the small Ir5+ moment."}],"review_version":1}