Electron magnetic circular dichroism (EMCD) is a powerful technique for estimating element-specific magnetic moments of materials on nanoscale with the potential to reach atomic resolution in transmission electron microscopes. However, the fundamentally weak EMCD signal strength complicates quantification of magnetic moments, as this requires very high precision, especially in the denominator of the sum rules. Here, we employ a statistical resampling technique known as bootstrapping to an experimental EMCD dataset to produce an empirical estimate of the noise-dependent error distribution resulting from application of EMCD sum rules to bcc iron in a 3-beam orientation. We observe clear experimental evidence that noisy EMCD signals preferentially bias the estimation of magnetic moments, further supporting this with error distributions produced by Monte-Carlo simulations. Finally, we propose guidelines for the recognition and minimization of this bias in the estimation of magnetic moments.

Cellulose, being a renewable and abundant biopolymer, has garnered significant attention for its unique properties and potential applications in hybrid materials. Understanding the hierarchical arrangement of cellulose nanofibers is crucial for developing cellulose-based materials with enhanced mechanical properties. In this study, the use of Scanning Electron Diffraction (SED) is presented to map the nanoscale orientation of cellulose fibers in a bio-composite material with a preserved wood cell structure. The SED data provides detailed insights into the ordering of cellulose with an extraordinary resolution of approximate to 15 nm. It enables a quantitative analysis of the fiber orientation over regions as large as entire cells. A highly organized arrangement of cellulose fibers within the secondary cell wall is observed, with a gradient of orientations toward the outer part of the wall. The in-plane fiber rotation is quantified, revealing a uniform orientation close to the middle lamella. Transversely sectioned material exhibits similar trends, suggesting a layered cell wall structure. Based on the SED data, a 3D model depicting the complex helical alignment of fibers throughout the cell wall is constructed. This study demonstrates the unique opportunities SED provides for characterizing the nanoscale hierarchical arrangement of cellulose nanofibers, empowering further research on a range of hybrid materials. Fundamental knowledge about the hierarchical arrangement of cellulose nanofiber is of great importance in developing new cellulose-based hybrid materials. Scanning electron diffraction is employed to map the cellulose nanofiber orientations throughout a wood-derived bio-based material. SED data reveals insights into cellulose alignment and enables precise quantitative fiber orientation analysis with a nanoscale spatial resolution.image

The need to acquire multiple angle-resolved electron energy loss spectra (EELS) is one of the several critical challenges associated with electron magnetic circular dichroism (EMCD) experiments. If the experiments are performed by scanning a nanometer to atomic-sized electron probe on a specific region of a sample, the precision of the local magnetic information extracted from such data highly depends on the accuracy of the spatial registration between multiple scans. For an EMCD experiment in a 3-beam orientation, this means that the same specimen area must be scanned four times while keeping all the experimental conditions same. This is a non-trivial task as there is a high chance of morphological and chemical modification as well as non-systematic local orientation variations of the crystal between the different scans due to beam damage, contamination and spatial drift. In this work, we employ a custom-made quadruple aperture to acquire the four EELS spectra needed for the EMCD analysis in a single electron beam scan, thus removing the above-mentioned complexities. We demonstrate a quantitative EMCD result for a beam convergence angle corresponding to sub-nm probe size and compare the EMCD results for different detector geometries.