Role of dopant incorporation on the magnetic properties of Ce1−xNixO2 nanoparticles: An electron paramagnetic resonance study
Bibliographic record
Abstract
Nickel doping has been found to produce weak room-temperature ferromagnetism (FM) in CeO2. The saturation magnetization (Ms) of the chemically synthesized Ce1−xNixO2 samples showed a maximum for x=0.04, above which the magnetization decreased gradually. For Ce1−xNixO2 samples with x⩾0.04, an activation process involving slow annealing of the sample to 500°C increased the Ms by more than two orders of magnitude. However, no such activation effect was observed in samples with x<0.04. Electron paramagnetic resonance (EPR) technique has been exploited to understand (i) the gradual decrease in the FM and subsequent disappearance of FM with increase in x for x>0.04, and (ii) the dramatic increase in Ms in the activated Ce1−xNixO2 samples with x⩾0.04 and the absence of this behavior in samples with x<0.04. Detailed analysis by simulation of the EPR data on several as-prepared Ce1−xNixO2 samples with 0.01⩽x⩽0.10 at 5 and 300K indicates the presence of several paramagnetic species: (i) two magnetically inequivalent Ni2+ ions with the ionic spin S=1, (ii) one Ce3+ ion with spin S=1∕2, and (iii) three O2− defects with S=1∕2. The spectra of the samples with x<0.04 are dominated by a single Ni2+ EPR line ascribed to dopant ions in substitutional sites, whereas in samples with x⩾0.04, there is an additional EPR line attributed to Ni2+ ions occupying interstitial sites. In the activated sample with x=0.08, the EPR line due to the interstitial Ni2+ ions is completely absent, and only the line due to substitutional Ni2+ ions is present, suggesting that the enhanced FM arises from migration of Ni2+ ions from interstitial to substitutional sites.
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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".