Neutron spectroscopic study of crystalline electric field excitations in stoichiometric and lightly stuffed<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Yb</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>Ti</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>7</mml:mn></mml:msub></mml:mrow></mml:math>
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Bibliographic record
Abstract
Time-of-flight neutron spectroscopy has been used to determine the crystalline electric field (CEF) Hamiltonian, eigenvalues and eigenvectors appropriate to the $J=7/2 {\mathrm{Yb}}^{3+}$ ion in the candidate quantum spin ice pyrochlore magnet ${\mathrm{Yb}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$. The precise ground state (GS) of this exotic, geometrically frustrated magnet is known to be sensitive to weak disorder associated with the growth of single crystals from the melt. Such materials display weak ``stuffing,'' wherein a small proportion, $\ensuremath{\approx}2%$, of the nonmagnetic ${\mathrm{Ti}}^{4+}$ sites are occupied by excess ${\mathrm{Yb}}^{3+}$. We have carried out neutron spectroscopic measurements on a stoichiometric powder sample of ${\mathrm{Yb}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$, as well as a crushed single crystal with weak stuffing and an approximate composition of ${\mathrm{Yb}}_{2+x}{\mathrm{Ti}}_{2\ensuremath{-}x}{\mathrm{O}}_{7+y}$ with $x=0.046$. All samples display three CEF transitions out of the GS, and the GS doublet itself is identified as primarily composed of ${m}_{J}=\ifmmode\pm\else\textpm\fi{}1/2$, as expected. However, stuffing at low temperatures in ${\mathrm{Yb}}_{2+x}{\mathrm{Ti}}_{2\ensuremath{-}x}{\mathrm{O}}_{7+y}$ induces a similar finite CEF lifetime as is induced in stoichiometric ${\mathrm{Yb}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$ by elevated temperature. We conclude that an extended strain field exists about each local ``stuffed'' site, which produces a distribution of random CEF environments in the lightly stuffed ${\mathrm{Yb}}_{2+x}{\mathrm{Ti}}_{2\ensuremath{-}x}{\mathrm{O}}_{7+y}$, in addition to producing a small fraction of Yb ions in defective environments with grossly different CEF eigenvalues and eigenvectors.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.003 | 0.002 |
| Meta-epidemiology (narrow) | 0.002 | 0.004 |
| Meta-epidemiology (broad) | 0.001 | 0.003 |
| Bibliometrics | 0.002 | 0.006 |
| Science and technology studies | 0.003 | 0.002 |
| Scholarly communication | 0.002 | 0.003 |
| Open science | 0.005 | 0.004 |
| Research integrity | 0.002 | 0.004 |
| Insufficient payload (model declined to judge) | 0.355 | 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 it