Neutron diffraction and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>μ</mml:mi><mml:mi>SR</mml:mi></mml:mrow></mml:math> studies of two polymorphs of nickel niobate <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>NiNb</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>6</mml:mn></mml:msub></mml:mrow></mml:math>
Bibliographic record
Abstract
Neutron diffraction and muon spin relaxation ($\ensuremath{\mu}\mathrm{SR}$) studies are presented for the newly characterized polymorph of ${\mathrm{NiNb}}_{2}{\mathrm{O}}_{6} (\ensuremath{\beta}\ensuremath{-}{\mathrm{NiNb}}_{2}{\mathrm{O}}_{6})$ with space group ${P4}_{2}/n$ and $\ensuremath{\mu}\mathrm{SR}$ data only for the previously known columbite structure polymorph with space group $Pbcn$. The magnetic structure of the ${P4}_{2}/n$ form was determined from neutron diffraction using both powder and single-crystal data. Powder neutron diffraction determined an ordering wave vector $\stackrel{P\vec}{k}=(\frac{1}{2},\frac{1}{2},\frac{1}{2})$. Single-crystal data confirmed the same $\stackrel{P\vec}{k}$ vector and showed that the correct magnetic structure consists of antiferromagnetically coupled chains running along the $a$ or $b$ axis in adjacent ${\mathrm{Ni}}^{2+}$ layers perpendicular to the $c$ axis, which is consistent with the expected exchange interaction hierarchy in this system. The refined magnetic structure is compared with the known magnetic structures of the closely related trirutile phases, ${\mathrm{NiSb}}_{2}{\mathrm{O}}_{6}$ and ${\mathrm{NiTa}}_{2}{\mathrm{O}}_{6}$. $\ensuremath{\mu}\mathrm{SR}$ data finds a transition temperature of ${T}_{N}\ensuremath{\sim}15\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ for this system, while the columbite polymorph exhibits a lower ${T}_{N}=5.7(3)$ K. Our $\ensuremath{\mu}\mathrm{SR}$ measurements also allowed us to estimate the critical exponent of the order parameter $\ensuremath{\beta}$ for each polymorph. We found $\ensuremath{\beta} =0.25(3)$ and 0.16(2) for the $\ensuremath{\beta}$ and columbite polymorphs, respectively. The single-crystal neutron scattering data give a value for the critical exponent $\ensuremath{\beta} =0.28(3)$ for $\ensuremath{\beta}\ensuremath{-}{\mathrm{NiNb}}_{2}{\mathrm{O}}_{6}$, in agreement with the $\ensuremath{\mu}\mathrm{SR}$ value. While both systems have $\ensuremath{\beta}$ values less than 0.3, which is indicative of reduced dimensionality, this effect appears to be much stronger for the columbite system. In other words, although both systems appear to be well described by $S=1$ spin chains, the interchain interactions in the $\ensuremath{\beta}$ polymorph are likely much larger.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.029 | 0.003 |
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".