Synthesis, Crystal Structure, Crystal Chemistry, and Magnetic Properties of PbMBO<sub>4</sub> (M = Cr, Mn, Fe): A New Structure Type Exhibiting One- Dimensional Magnetism
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Bibliographic record
Abstract
The crystal chemistry of a new structure type found in the Pb−M−B−O system, PbMBO 4 (M = Al, Ga), was extended to include M = Cr, Mn, and Fe. Extension to other trivalent ions, such as Ti, V, Co, Sc, In, and Y, failed for various reasons. Single crystals were grown from a PbO flux for M = Mn and Fe and the crystal structures were solved from X-ray single-crystal diffraction data. For M = Cr, the structure was refined from neutron powder diffraction data. The crystal structure is described in Pnma and features chains of edge-sharing MO 6 octahedra extended along the b -axis. Rigid, planar BO 3 groups bridge the MO 6 octahedra both within and between the chains, forcing the two M−O−M bridging angles involved in the shared edge to be highly asymmetric and constraining the M−M distances to be roughly constant at 2.97 Å. In all cases, one-dimensional short-range magnetic correlations were observed in the magnetic susceptibility data which were antiferromagnetic for M = Cr and Fe and ferromagnetic for M = Mn. Values for the intrachain exchange, J / k B, were extracted from fits to standard models and were −4, −26, and +11 K for M = Cr, Fe, and Mn, respectively. Long-range order was observed below 8.3, 31, and 125 K for M = Cr, Mn, and Fe, respectively, and magnetic structures were refined from neutron powder diffraction data. PbCrBO 4 and PbFeBO 4 both show antiferromagnetic long-range order with the b -axis antiferromagnetic chains coupled ferromagnetically, while for PbMnBO 4 both intra- and interchain couplings are ferromagnetic. Thus, this latter material is a rare example of a ferromagnetic insulator. Attempts to rationalize the observed intrachain J / k B values by reference to magneto-structural correlations were largely unsuccessful due to a lack of appropriate model compounds.
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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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.007 | 0.000 |
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