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
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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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 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".