A new series of rare-earth iron carbides R|2Fe|1|5Si|2C[subscript y]
Bibliographic record
Abstract
$\\rm R\\sb2Fe\\sb{17}N\\sb{y}$ and $\\rm R\\sb2Fe\\sb{17}C\\sb{y}$ have attracted much attention because of their excellent intrinsic magnetic properties. However, these nitrides and carbides prepared by a gas-phase reaction have a major drawback, namely their chemical or structural instability at high temperature. We have discovered that Si substitution is able to stabilize the 2:17 structure of the carbides. A new series, $\\rm R\\sb2Fe\\sb{15}Si\\sb2C\\sb{y}$ (R = Nd, Sm, Gd and Er), has been prepared by heating powders of their parents in CH$\\sb4$ gas at 700$\\sp\\circ$C instead of usual 500$\\sp\\circ$C. For these carbides, the carbon concentrations are close to the theoretical value of y = 3 and the 2:17 structure is still retained up to 700$\\sp\\circ$C. Therefore, it is possible to make these carbides into the anisotropic permanent magnets by aligning and then sintering. The crystal structures, the Curie temperatures, the saturation magnetizations, the temperature dependences of the magnetization, the magnetic anisotropies and the spin reorientation transitions of $\\rm \\sb2Fe\\sb{15}Si\\sb2C\\sb{y}$ have been studied by x-ray diffraction and magnetic measurements. These carbides have elevated Curie temperatures as well as other magnetic properties that are modified as compared to their parents. For $\\rm Sm\\sb2Fe\\sb{16}SiC\\sb{2.7},$ the Curie temperature is 660 K; the anisotropy field and saturation magnetization at room temperature are 95 kOe and 92 emu/g, respectively. The origin of the unexpected decrease in the magnetization is discussed. The hyperfine fields, the distribution of Fe and Si atoms on each Fe site and the temperature dependence of the hyperfine parameters have been studied by Mossbauer spectra in an attempt to unravel the magnetic properties of these carbides on an atomic scale. The exchange integrals as a function of the distance between the Fe-Fe pairs have been obtained; the relationships between the Curie temperature and the site occupancy of Si atoms have been found. A negative exchange interaction model is proposed to interpret the origin in the greatly elevated Curie temperature for the nitrides and carbides and to predict the Curie temperatures of $\\rm R\\sb2(FeSi)\\sb{17}$ compounds; this model is consistent with the experimental results.
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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) | 0.002 | 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".