| 1. |
- Ali, Hasan, 1985-, et al.
(author)
-
Single scan STEM-EMCD in 3-beam orientation using a quadruple aperture
- 2023
-
In: Ultramicroscopy. - : Elsevier BV. - 0304-3991 .- 1879-2723. ; 251
-
Journal article (peer-reviewed)abstract
- 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.
|
|
| 2. |
- Ulusoy, Seda, et al.
(author)
-
Elucidating the Lithiation Process in Fe3−δO4 Nanoparticles by Correlating Magnetic and Structural Properties
- 2024
-
In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 16:12, s. 14799-14808
-
Journal article (peer-reviewed)abstract
- Due to their high potential energy storage, magnetite (Fe3O4) nanoparticles have become appealing as anode materials in lithium-ion batteries. However, the details of the lithiation process are still not completely understood. Here, we investigate chemical lithiation in 70 nm cubic-shaped magnetite nanoparticles with varying degrees of lithiation, x = 0, 0.5, 1, and 1.5. The induced changes in the structural and magnetic properties were investigated using X-ray techniques along with electron microscopy and magnetic measurements. The results indicate that a structural transformation from spinel to rock salt phase occurs above a critical limit for the lithium concentration (xc), which is determined to be between 0.5< xc ≤ 1 for Fe3−δO4. Diffraction and magnetization measurements clearly show the formation of the antiferromagnetic LiFeO2 phase. Upon lithiation, magnetization measurements reveal an exchange bias in the hysteresis loops with an asymmetry, which can be attributed to the formation of mosaic-like LiFeO2 subdomains. The combined characterization techniques enabled us to unambiguously identify the phases and their distributions involved in the lithiation process. Correlating magnetic and structural properties opens the path to increasing the understanding of the processes involved in a variety of nonmagnetic applications of magnetic materials.
|
|
