Quantifying magnetism on the nanometer scale: <scp>EMCD</scp> on individual <scp>FePt</scp> nanoparticles
Bibliographic record
Abstract
Electron energy‐loss magnetic chiral dichroism (EMCD), which is the electron wave analogue of X‐ray magnetic circular dichroism (XMCD), offers the possibility to study magnetic properties at the nanoscale in a TEM. The relatively young method of EMCD [1] was already refined to such an extent that it is possible to probe magnetic moments of thin films of a variety of ferromagnets [2, 3, 4]. By now, these measurements already surpass the resolution of XMCD experiments. However, quantitative EMCD measurements are so far only reported on thin films rather than on nanoparticles, which are expected to reveal distinct magnetic properties due to their reduced dimensions and enhanced surface to volume ratio. We report on EMCD measurements on a single FePt nanoparticle (cf. Figure 1) and compare our experimental findings with simulations. L1 0 ordered FePt is a particularly interesting material since it offers the highest magneto‐crystalline anisotropy among the oxidation‐resistant hard magnets [5]. It is therefore a promising material for future high density magnetic data storage media. The L1 0 ordered FePt nanoparticles on a STO substrate were prepared by sputtering. Prior to the spectroscopic measurements, samples in plan view geometry were subjected to mechanical thinning and grazing incidence Ar + ion milling in order to obtain 10 nm thick substrate‐free nanoparticles. The experiments were performed on a FEI Titan 3 80‐300 microscope equipped with an image C S corrector. The sample was oriented in three beam condition with the [001] easy axis of L1 0 FePt oriented (close to) parallel to the electron beam. Binned‐gain acquisition of the EEL spectra was used to optimize the S/N ratio [6]. Particular attention was paid to the analysis of the EEL spectra. A measurement route is presented that allows for the extraction of a dichroic signal from spectra that still suffer from non‐optimal S/N ratio. Our experiments are supported by simulations of EEL spectra utilizing the WIEN2k program package [7] in combination with Bloch‐wave (BW) methods. These simulations are used to (pre‐)determine optimal experimental parameters, that provide for the highest EMCD signals [8, 9]. The experiments reveal a small but reproducible dichroic signal (cf. Figure 2) that agrees well with the results of the theoretical calculations. From these experimental spectra, a ratio of angular to spin magnetic moment m l /m s = 0.08 ± 0.08 is for the first time quantitatively derived for individual FePt nanoparticles [10], which agrees well with the XMCD result m l /m s = 0.09 for a large ensemble of L1 0 ordered FePt nanoparticles [11].
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.003 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 0.017 |
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; both teacher heads agree on what is shown here.
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".