The partitioning of Dy and Tb in NdFeB magnets: A first-principles study
Bibliographic record
Abstract
Doping with Dy/Tb is a current solution to improve the coercivity and the operating temperature of NdFeB magnets, by increasing the magnetocrystalline anisotropy of the (Nd, Dy/Tb)2Fe14B (2:14:1) phase. The efficiency of Dy/Tb doping depends on the distribution of Dy/Tb in the multi-phase microstructure of the NdFeB magnet. To understand and control the Dy/Tb redistribution, the partitioning of Dy/Tb between 2:14:1 and Nd-rich phases has been studied by a first-principles density functional calculation. The total energy calculations indicate that Dy and Tb prefer to enter the 4f sites in the 2:14:1 phase. The substitution energies of Dy and Tb in 2:14:1 are negative and are −0.35 eV/atom and −0.33 eV/atom, respectively, as Nd is replaced with 25% of Dy/Tb, i.e., stabilizing the 2:14:1 structure. However, the substitution energies of Dy and Tb in NdO have large positive values. They are 0.83 eV/atom and 0.73 eV/atom for Dy and Tb, respectively, when 25% of Nd is replaced by Dy/Tb. The results indicate that Dy/Tb prefer to enter the 2:14:1 phase rather than the Nd-rich phase (NdO). This is the thermodynamic origin for the selective occupation of Dy and Tb in the 2:14:1 structure which enhances the magnetic anisotropy field.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.002 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 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".