# Eu-doped nickelates: re-entrance without a settled pairing mechanism

Separate sample-specific zero resistance, diamagnetic screening and resistance-contour criteria in Sm/Ca/Eu infinite-layer films; keep exchange compensation, magnetic order and pairing symmetry as distinct questions.

## Review scope

Selected passages and figures in author manuscript arXiv:2508.14666v3 (25 April 2026), compared with the publisher abstract. The complete final published text has not been checked.

- Author self-review, not independent scientific review or a reproduction of the transport measurements.
- The later author version is not assumed identical to the final journal article; full final text, correction history, calibration and raw-data analysis remain open.
- Resistance-contour criteria, zero resistance and screening are different observables. None alone settles the magnetic structure or pairing symmetry.

## Identify the material and the version

Yang and colleagues study Sm0.95−xCa0.05EuxNiO2 (SCEₓ), an infinite-layer nickelate film series with fixed nominal Ca substitution. It is not Eu-substituted bilayer La3Ni2O7. The measured Eu valence is mixed and varies with composition, so nominal x is not a direct count of identical Eu²⁺ moments.

This note reads the revised author manuscript dated 25 April 2026. The journal article was published online on 23 April 2026. The publisher abstract supports the broad re-entrance report, but access to that abstract does not establish equivalence of all final and author-version figures. The separate Nd/Eu nickelate study discussed in G3 and G5 concerns another material series; its magnetic interpretation cannot simply be transferred here.

Evidence: experiment. Source relationship: direct-support. Sources: yang-author-v3.

## Keep each field scale with its sample and criterion

The selected author text and Figure 2 distinguish the following observations. Fields are perpendicular to the film plane (H∥c) for these comparisons.

| Sample | Temperature or protocol | Reported observation | Interpretation boundary |
| --- | --- | --- | --- |
| SCE0.34, about 54 unit cells | 2 K transport | Zero resistance returns above about 6.23 T | Recovery field, not a universal upper critical field |
| Same SCE0.34 specimen | Temperature sweeps at fixed field | Mutual-inductance screening at 9 and 12 T; absent at 3 T | Supports the superconducting interpretation; no bulk volume fraction is inferred here |
| SCE0.32 | 3 K transport | Resistance returns to zero near 13.04 T | Not the upper boundary of the high-field phase |
| SCE0.32 | 1.7 K transport | High-field zero resistance persists above about 32 T | Different temperature from the 13.04 T statement |

These temperatures describe measurement conditions, not interchangeable transition temperatures. Figure 3 instead marks open-circle phase boundaries using 0.5Rn, with Rn the high-field normal-state resistance. Those contours must not be relabeled zero-resistance boundaries. No material-Tc record is created from this table.

Evidence: experiment. Source relationship: direct-support. Sources: yang-author-v3.

## Angular behavior and an unresolved inherited number

The angle θ is measured from the film normal. The angular maps use different temperatures: 4.2 K for x=0.33 and 0.36, 1.5 K for x=0.38, and 0.3 K for x=0.40. Their changing angular windows cannot support a universal assertion that in-plane re-entrance is absent. The manuscript also distinguishes intermediate-doping compensation-like behavior from stronger deviations at x=0.40.

The inherited notes attribute persistence to 45 T at 0.3 K to SCE0.36. That exact sample–temperature–field tuple was not verified in the selected v3 pages. Extended Data Figure 9 labels SCE0.36 at 4.2 K and SCE0.40 at 0.3 K; it also has a caption saying “up to 45 T” although its upper panels extend to 60 T. These version and panel details require resolution before the inherited tuple is used as a current verified result. A measurement ceiling would in any case provide a bound, not a measured high-field endpoint.

Evidence: experiment. Source relationship: direct-support. Sources: yang-author-v3.

## What the magnetic evidence can and cannot establish

Nonlinear Hall response after linear-background subtraction and hysteretic magnetoresistance motivate magnetic explanations. They do not by themselves identify uniform ferromagnetism, its volume fraction, or a particular pairing state. The v3 discussion explicitly leaves long-range magnetic order and its structure undetermined.

The authors fit a WHH-based model including orbital and Pauli pair breaking, spin-orbit scattering and an exchange field. Compensation partially describes intermediate compositions; the fitted exchange fields and scattering parameters remain phenomenological. An empirical factor of two in a Brillouin-function argument improves some fits but is not universal and does not adequately describe x=0.40. Neither this adjustment nor analogy with other re-entrant systems proves spin-triplet pairing.

Evidence: theory. Source relationship: direct-support. Sources: yang-author-v3.

## Use the result across the Wiki

D5 supplies the material-family context; D15 separates substitution, scattering and magnetism; G3 and G5 distinguish re-entrance from a demonstrated compensation mechanism. For H7 and H9, superconducting recovery fields must not become Hall-sign-reversal or anomalous-Hall threshold fields. This note reports no extracted ordinary Hall coefficient.

A stronger scientific assessment still needs version-resolved final figures, criterion and noise-floor checks, sample calibration and local magnetic probes. The present review neither fits the deposited source-data files nor certifies an intrinsic bulk phase or unique microscopic mechanism.

Evidence: hypothesis. Source relationship: context-for-editorial-analysis. Sources: yang-author-v3.

## Sources

yang-author-v3: Mingwei Yang and colleagues. [Field re-entrant superconductivity in Eu-doped infinite-layer nickelates](https://arxiv.org/abs/2508.14666v3). preprint; Author version revised 2026-04-25; arXiv:2508.14666v3; first submitted 20 August 2025; later author manuscript associated with the published article. Selected pages 2, 4–8, 12–14; Figure 2 (page 19), Figure 3 (page 20), and Extended Data Figure 9 (page 30) inspected. Full final-version equivalence and raw-data reproduction unverified. Source license: [CC BY 4.0 (author version)](https://creativecommons.org/licenses/by/4.0/). Editorial wording and organization changed.

yang-journal: Mingwei Yang and colleagues. [Field re-entrant superconductivity in Eu-doped infinite-layer nickelates](https://doi.org/10.1038/s41586-026-10547-y). journal-article; Published online 2026-04-23; Nature 653, 1052–1059 (2026); publisher abstract only checked. Previously accessible publisher abstract and publication metadata. Complete final text is subscription restricted; the later author manuscript supplies the detailed selected evidence in this note.

## Editorial corrections

- Magnetic order and pairing: Retain the observed transport and screening, while magnetic order, pairing symmetry and a unique mechanism remain unresolved.
- Angular dependence: Retain sample-specific angle and temperature dependence, including the broader windows in higher-doping specimens.
- Unverified inherited 45 T tuple: Do not carry this tuple as verified by v3: selected later panels use SCE0.36 at 4.2 K and SCE0.40 at 0.3 K. Final/version reconciliation remains open.
- Threshold and contour criteria: Keep 6.23 T and 13.04 T with their specific samples and temperatures; distinguish zero resistance from the 0.5Rn contour criterion.
- Screening and Hall scope: Describe mutual-inductance diamagnetic screening without deriving bulk volume fraction; do not invent Hall coefficients or reversal fields.

## Provenance

papers/CROSS_D5_D15_Yang2026.md; commit 0a7c9d6696804ec26aa12f8eed68b55c9b3c0fcf; SHA-256 33970aef30ac6c132f95921ae2553d6662681ba11301ae6daf97d4a0a056d6a6; merge-into. Coverage: Whole source-note disposition; the primary scientific review remains limited to the stated scope.

papers/library/Yang_Eu-IL-Nickelate-Reentrant-SC_READING_NOTES.md; commit 0a7c9d6696804ec26aa12f8eed68b55c9b3c0fcf; SHA-256 7c02489fdb5faf31238beec381fadf8a49c3e9a9fbb33426f7a2011b216fbd47; merge-into. Coverage: Whole source-note disposition; the primary scientific review remains limited to the stated scope.

Original editorial synthesis adapted from Mingwei Yang and colleagues' CC BY 4.0 author manuscript, linked below. Wording, organization and cross-topic analysis have changed; no source figures are reproduced. The journal version and third-party materials retain their own stated rights.

Note ID: yang-eu-nickelate-reentrance. Revision: 9f57bca48151c4275ba8.