The measurement of off‐plane magnetic field through electron vortex beams
Bibliographic record
Abstract
It is well known that a magnetic field produces a phase change proportional to the in plane magnetic field B [1]. Alas the out of plane magnetic field is more elusive. The only measurement that so far seems to produce any out of plane information is the magnetic dichroism [2] as it actually measures the out of plane magnetization. Unfortunately magnetic dichroism experiment is still a complicated experiment that requires a considerable control of the condition and of the material; moreover the measures of the magnetization , often with the objective on, is not directly a measure of the magnetic field itself. However while a plane wave along the optical axis has no significant interaction with a magnetic field along z , vortex beams with winding number l do feel such field through a Larmor phase effect. We will demonstrate here that through the use of large vortex beams [3][4][5] we are able, for the first time, to measure the out of plane magnetic field generated by a magnetic pillar of Co [6]. We placed the vortex around the pillar ensuring as much as possible an axial symmetry and observed the phase effect. The result is in good agreement with the typical magnetization expected for the pillar with an average field at surface of about 2T. Fig 1 illustrates the A and B field produced by a magnetic pillar. The actual magnetic pillar fabricated by EBID deposition is illustrated in fig 1b. Fig 2 depicts the vortex beam density with L=200 as imaged in its focal plane. Thanks to an interferometric approach we were able to measure the magnetic phase contribution and bind it to the magnetic field in proximity of the sample. The magnetic phase is visible in the inset of fig 2 showing approximate axial symmetry. The technique has been carried on in Low Mag mode with the main objective lens off but there are no principle limitation to the application in conventional (S) TEM mode. Moreover this promises to be one of the best recognition of the importance of vortex beams in microscopy for material science.
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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 | 0.001 | 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".