Structure and Magnetic Properties of KRuO<sub>4</sub>
Bibliographic record
Abstract
The crystal structure of KRuO 4 is refined at both 280 and 3.5 K from neutron powder data, and magnetic properties are reported for the first time. The scheelite structure, I 4 1 / a, is confirmed at both temperatures. Atomic positions of greater accuracy than the original 1954 X-ray study are reported. The rare Ru 7+ ion resides in a site of distorted tetrahedral symmetry with nominal electronic configuration 4d 1 (e 1 ). Curie–Weiss parameters are near free ion values for the effective moment and θ = −77 K, indicating dominant antiferromagnetic (AF) correlations. A broad susceptibility maximum occurs near 34 K, but long-range AF order sets in only below 22.4 K as determined by magnetization and heat capacity data. The entropy loss below 50 K is only 44% of the expected R ln 2, indicating the presence of short-range spin correlations over a wide temperature range. The Ru sublattice consists of centered, corner-sharing tetrahedra which can lead to geometric frustration if both the nearest-neighbor, J 1, and the next-nearest-neighbor, J 2, exchange constants are AF and of similar magnitude. A spin dimer analysis finds J 1 / J 2 ≈ 25, indicating weak frustration, and a (d z 2 ) 1 ground state. A single, weak magnetic reflection was indexed as (110). The absence of the (002) magnetic reflection places the Ru moments parallel to the c axis. The Ru 7+ moment is estimated to be 0.57(7) μ B, reduced from an expected value near 1 μ B . A recent computational study of isostructural, isoelectronic KOsO 4 predicts a surprisingly large orbital moment due to spin–orbit coupling (SOC). However, the free ion SOC constant for Ru 7+ is only ∼30% that of Os 7+, so it is unclear that this effect can be implicated in the low ordered moment for KRuO 4 . The origin of the short-range spin correlations is also not understood.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".