Static magnetic order in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Na</mml:mi></mml:mrow><mml:mrow><mml:mn>0.75</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">CoO</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>detected by muon spin rotation and relaxation
Bibliographic record
Abstract
The nature of the magnetic transition of the Na-rich thermoelectric ${\mathrm{Na}}_{0.75}{\mathrm{CoO}}_{2}$ at 22 K was studied by positive muon-spin-rotation and relaxation $({\ensuremath{\mu}}^{+}\mathrm{SR})$ spectroscopy, using a polycrystalline sample in the temperature range between 300 and 2.5 K. Zero-field $\ensuremath{\mu}\mathrm{SR}$ measurements indicated the existence of a static internal magnetic field at temperatures below 22 K ${(=T}_{\mathrm{m}}).$ The observed muon-spin precession signal below ${T}_{\mathrm{m}}$ consisted of three components with different precession frequencies, corresponding to three inequivalent ${\ensuremath{\mu}}^{+}$ sites in the ${\mathrm{Na}}_{0.75}{\mathrm{CoO}}_{2}$ lattice. The total volume fraction of the three components was estimated as $\ensuremath{\sim}21%$ at 2.5 K; thus, this magnetic transition was not induced by impurities but is an intrinsic change in the magnetism of the sample, although the sample was magnetically inhomogeneous otherwise. On the other hand, a similar experiment on a ${\mathrm{Na}}_{0.65}{\mathrm{CoO}}_{2}$ sample exhibited no magnetic transition down to 2.5 K; which indicates that the average valence of the Co ions is responsible for inducing the magnetic transition at 22 K.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.222 | 0.055 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".