Transmission Soft X-ray Research Articles

Scanning Transmission Soft X-Ray Microscopy Probes Topical Drug Delivery of Rapamycin Facilitated by Microneedles.

Scanning Transmission X-ray microscopy (STXM) is a sensitive and selective probe for the penetration of rapamycin which is topically applied to human skin ex vivo and is facilitated by skin treatment with microneedles puncturing the skin. Inner-shell excitation serves as a selective probe for detecting rapamycin by changes in optical density as well as linear combination modeling using reference spectra of the most abundant species. The results indicate that mechanical damage induced by microneedles allows this drug to accumulate in the stratum corneum without reaching the viable skin layers. This is unlike intact skin which shows no drug penetration at all and underscores the mechanical impact of microneedle skin treatment. These results are compared to drug penetration profiles of other drugs highlighting the importance of skin barriers. High spatial resolution studies also indicate that the lipophilic drug rapamycin is observed in corneocytes. Attempts in data evaluation are reported to probe rapamycin also in the lipid layers between the corneocytes, which was not accomplished before. These results are compared to recent results on rapamycin uptake in skin where barrier impairment was induced by pre-treatment with the enzyme trypsin and drug formulations leading to occlusion.

Soft X-ray spectromicroscopy of human fibroblasts with impaired sialin function.

Salla disease (SD) is a lysosomal storage disease where free sialic acid (SA) accumulates in lysosomes due to the impaired function of a membrane protein, sialin. Synchrotron radiation-based scanning transmission soft X-ray spectromicroscopy (STXM) was used to analyze both SD patients' fibroblasts and normal human dermal fibroblasts (NHDF) from healthy controls. Both cell lines were also cultured with N-acetyl-d-mannosamine monohydrate (ManNAc) to see if it increased SA concentration in the cells. The STXM technique was chosen to simultaneously observe the morphological and chemical changes in cells. It was observed that free SA did not remain in the lysosomes during the sample processing, leaving empty vacuoles to the fibroblasts. The total cytosol and entire cell spectra, however, showed systematic differences between the SD and NHDF samples, indicating changes in the relative macromolecular concentrations of the cells. The NHDF cell lines contained a higher relative protein concentration compared to the SD cell lines, and the addition of ManNAc increased the relative protein concentration in both cell lines. In this study, two sample preparation methods were compared, resin-embedded thin sections and cells grown directly on sample analysis grids. While the samples grown on the grids exhibited clean, well-resolved spectra not masked by embedding resin, the low penetration depth of soft X-rays hindered the analysis to only the thin region of the microfilaments away from the thick nucleus.

Interface sharpness in stacked thin film structures: a comparison of soft X-ray reflectometry and transmission electron microscopy

Interface sharpness in stacked thin film structures: a comparison of soft X-ray reflectometry and transmission electron microscopy

Spatiotemporal Active Phase Evolution for CO2 Electrocatalysis

Transition-metal-based solid-state electrocatalysts undergo dynamic phase transformation governed by the local electrochemical environment during operation, e.g., oxygen evolution/reduction(1,2), hydrogen evolution(3), and carbon dioxide reduction(4). Electrochemical active species, often hidden before operation, can become evolved due to the applied electrochemical potential and/or surrounding chemicals. These species are stabilized under the local environment dynamically generated by the reaction product, e.g., proton (H+) or hydroxyl (OH-) group(5,6).Active species often account for a small fraction (i.e., minor motif) of the entire catalyst volume, and the nanoscale morphology and chemical composition of the electrocatalyst are inhomogeneous and continuously change during the electrochemical reaction. Thus, capturing the active species remains a major challenge. Spatiotemporal observation of the structural/chemical changes of the electrocatalyst and the correlation with the local electrochemical environment may reveal the active species and elucidate the governing step toward their formation. Furthermore, identification of the key intermediate step of catalyst phase transformation allows the redirection of low- to high-active catalysts; however, this remains challenging.During electrochemical CO2 reduction (ECR), (hydr)oxide-derived Cu electrocatalysts experience significant phase transformation and show high activity and selectivity for carbon dimerization (C–C coupling)(7,8,9). The location and chemical composition of the active species evolving during electrochemical phase transformation may be strongly heterogeneous; however, these species have not been clearly determined. Recent studies have employed operando characterization techniques, e.g., fluorescence hard/soft X-ray(4,10), X-ray photoelectron(11), and Raman spectroscopy(6), to elucidate the active species responsible for high C–C coupling activity. However, although these techniques could track the changes in chemical composition of the electrocatalysts during operation, they did not reveal the spatiotemporal evolution of the active species or existence of minor motifs, owing to their inefficient chemical sensitivity. Thus, it is imperative to develop an operando analysis technique that can probe the nanoscopic chemical composition with high spatial/temporal resolution and sufficient detection limit.By observing the chemical and morphological evolution of highly efficient ECR catalysts during operation, we identified the key intermediate species toward highly active surfaces and significantly enhanced the C–C coupling activity. Operando transmission soft X-ray microscopy(1,12,13), which visualizes the nanoscale chemical composition distribution of Cu-based catalysts during ECR, revealed that partially evolved Cu+ phases and surface Cu2+ phases are responsible for the dynamic dissolution–redeposition process(4,8) and improvement of C–C coupling activity, respectively. We further demonstrated that the dissolution–redeposition process is electrochemically triggered by inducing Cu+ phases, which are redirected to copper-carbonate-hydroxide species(6,14,15) even under high cathodic potentials. DFT calculations suggest that these cationic Cu species potentially serve as active species and/or assistive sites for enhancing C–C coupling activity.(1) Mefford, J. T., et al. Nature 593(7857), 67-73 (2021)(2) Kreider, M. E., et al. ACS Applied Materials & Interfaces 11(30), 26863-26871 (2019)(3) Zhai, L., et al. ACS Energy Letters 5(8), 2483-2491 (2020)(4) De Luna, P., et al. Nature Catalysis 1(2), 103-110 (2018)(5) Wang, Y., et al. Nature Catalysis 3(2), 98-106 (2020)(6) Henckel, D. A., et al. ACS Catalysis 11(1), 255-263 (2021)(7) Lee, S. Y., et al. Journal of the American Chemical Society 140(28), 8681-8689 (2018)(8) Zhong, D., et al. Angewandte Chemie International Edition 60(9), 4879-4885 (2021)(9) Lei, Q., et al. Journal of the American Chemical Society 142(9), 4213-4222 (2020)(10) Eilert, A., et al. The Journal of Physical Chemistry Letters 7(8), 1466-1470 (2016)(11) Arán-Ais, R. M., et al. Nature Energy 5(4), 317-325 (2020)(12) Lim, J. et al. Science 353, 566–571 (2016)(13) de Smit, E., et al. Nature 456(7219), 222-225 (2008)(14) Spodaryk, M., et al. Electrochimica Acta 297, 55-60 (2019)(15) Jiang, S., et al. ChemSusChem 15(8), e202102506 (2022) Figure 1

Electrochemical, Structural, and Hyperspectral Imaging Investigation of Bifunctional Zn-Air Battery Gas-Diffusion Electrodes

Rechargeable Zinc-air batteries (RZAB) emerge as highly promising solutions for electrochemical energy storage (EES) applications. Nevertheless, a noteworthy drawback in the existing generation of these batteries lies in the air gas-diffusion electrode (GDE). This component grapples with issues related to both efficiency and durability. In response to this challenge, our research is concentrated on the creation of a novel GDE, accompanied by an in-depth examination of its electrochemical, structural, and compositional characteristics. The primary objective is to comprehensively assess the physico-chemical factors that exert an influence on its efficiency and durability. In the case of the present research, two different catalysts were chosen for the ORR (discharge) and OER (charge) electrocatalysis, namely α-MnO2 nanorods (NR) and Ni nanoparticles (NP), respectively. The GDEs were produced by applying a water-based catalyst ink, augmented with PTFE and C-black, through spray-coating onto a carbon paper support, which serves as the gas diffusion layer (GDL). Initially, the ideal proportion of OER/ORR catalyst was determined by conducting electrochemical tests on both the individual material (via RRDE studies) and the gas diffusion electrode using a rapid screening protocol. The material extracted from the GDEs, in pristine state and after ageing under operating conditions, was then characterized with electrochemical methods, SEM microscopy, HRTEM/SAED microscopy/electron diffraction, as well as with direct- and Fourier-space soft x-ray transmission microscopy (STXM) at the Mn, Ni and Zn L-edges. The electrochemical tests conducted in this study demonstrated a progressive improvement in performance as the nickel nanoparticle content increased, until a plateau is reached after 23% wt. Specifically, lower overpotentials were observed alongside increased cyclic stability for the combined ORR/OER processes. These assessments were conducted in two distinct electrolyte environments: pure KOH and KOH with the inclusion of Zn2+. The inclusion of Zn2+ aimed to replicate and understand the potential impact of anode chemistry on the cathode's overall performance. The investigation employed HRTEM and SAED analyses to meticulously monitor alterations in the crystal structure of the α-MnO2 electrocatalyst under diverse aging conditions. Notably, during ORR cycling, the manganese nanorods underwent amorphization. However, cyclic processes between oxygen OER and ORR revealed the recovering of the original crystalline phase. The introduction of Zn2+ into the system resulted in the formation of a partially amorphous Zn-Mn mixed oxide. To delve further into the nuanced changes, soft-X ray hyperspectral imaging, both in direct and Fourier space was employed. By spectral imaging at the Mn and Ni L-edges, we could assess the space-dependent valence alterations of Manganese and Nickel at different stages of aging with space resolution down to a few tens of nanometers. The integration of diverse analytical techniques, including electrochemical assessments, STXM, HRTEM/ SAED imaging, along with space-resolved structural analyses, has provided a comprehensive, molecular-level understanding of the performance and degradation of bifunctional ORR/OER electrocatalysts within the realistic context of gas diffusion electrodes. Of particular significance is the capability of this combined approach to meticulously trace and correlate the changes in the chemical state of the manganese ORR electrocatalyst. This shift, notably away from the optimal 3+/4+ mixed valence state, was observed in response to aging and Zn2+ contamination. The correlation of this chemical state drift with electrochemical conditions and the evolution of crystal structure adds a nuanced layer of insight into the intricate interplay of factors influencing the performance and degradation of these electrocatalysts. In particular, the control of the oxidative stress under OER, enabled by addition of Ni NPs, was correlated with preservation of α-MnO2 crystallinity, GDE operation in the presence of Zn2+ was proved to give rise to the formation of ZnMn2O4, poisoning the electrocatalyst. Lastly, the role of hydrophobicity of the active layer of the GDE was proven to be of crucial importance in the stability of the Mn-based catalyst, as PTFE-surrounded clusters were observed to be less affected by cycling with respect to others which clearly underwent electrolyte flooding. Figure 1

In Situ Studies of Cu Catalyzed CO2 Electro-Reduction by Soft X-ray Scanning Transmission X-ray Microscopy and Soft X-ray Spectro-Ptychography

In Situ Studies of Cu Catalyzed CO2 Electro-Reduction by Soft X-ray Scanning Transmission X-ray Microscopy and Soft X-ray Spectro-Ptychography

Observation of mammalian living cells with femtosecond single pulse illumination generated by a soft X-ray free electron laser

Soft X-ray transmission microscopy is a powerful tool for visualizing cellular structures due to the natural contrast between organic material and water, but radiation damage has hindered its application to living cells. We have developed a soft X-ray microscope using femtosecond pulse illumination generated by a soft X-ray free electron laser, with which structural change of cells caused by radiation damage is negligible. Employing Wolter mirrors for illumination and objective optics allowed us to perform soft X-ray imaging with a large field of view, enabling observation of mammalian cells. We successfully captured images of living cells in a culture medium visualizing their carbon distribution. The broad wavelength-tunability of soft X-ray free electron lasers, in conjunction with the achromaticity of Wolter mirrors, enabled wavelength resolved cellular imaging.

Direct Observation of Room-Temperature Magnetic Skyrmion Motion Driven by Ultra-Low Current Density in Van Der Waals Ferromagnets.

The recent discovery of room-temperature ferromagnetism in 2D van der Waals (vdW) materials, such as Fe3GaTe2 (FGaT), has garnered significant interest in offering a robust platform for 2D spintronic applications. Various fundamental operations essential for the realization of 2D spintronics devices are experimentally confirmed using these materials at room temperature, such as current-induced magnetization switching or tunneling magnetoresistance. Nevertheless, the potential applications of magnetic skyrmions in FGaT systems at room temperature remain unexplored. In this work, the current-induced generation of magnetic skyrmions in FGaT flakes employing high-resolution magnetic transmission soft X-ray microscopy is introduced, supported by a feasible mechanism based on thermal effects. Furthermore, direct observation of the current-induced magnetic skyrmion motion at room temperature in FGaT flakes is presented with ultra-low threshold current density. This work highlights the potential of FGaT as a foundation for room-temperature-operating 2D skyrmion device applications.

In Situ Studies of Copper-Based CO2 Reduction Electrocatalysts by Scanning Transmission Soft X-ray Microscopy.

A microfluidic-enabled electrochemical device has been developed to investigate electrochemically active nanomaterials under reaction conditions using in situ scanning transmission soft X-ray microscopy (STXM). In situ STXM measurements were conducted on electrodeposited Cu catalysts under electrochemical CO2 reduction (CO2R) conditions. The study provides detailed, quantitative results about the changes in the morphology and chemical structure of the catalytic nanoparticles as a function of applied potentials. The deposited Cu nanoparticles initially contain both Cu(0) and Cu(I). As an increasingly cathodic potential is applied, the Cu(I) species gradually convert to Cu(0) over the potential range of +0.4 to 0 V versus the reversible hydrogen electrode (VRHE). During this process, Cu(I) particles of various sizes are converted to metallic Cu at different reaction rates and at slightly different potentials, indicating a degree of heterogeneity in the electrochemical response of discrete particles. At CO2R relevant potentials, only metallic Cu is observed, and the morphology of the particles is fairly stable within the spatial resolution limits of STXM (∼40 nm). We also report in situ STXM studies of a working electrode with relatively thick Cu-based electrodeposits. The spatially resolved chemical analysis identifies that Cu-oxide species can persist under CO2R conditions, but only when the catalytic nanoparticles are electronically isolated from the working electrode and therefore are catalytically irrelevant. In summary, in situ STXM is presented as a technique to gain advanced morphological and spatially resolved chemical structure insights into electrochemically active nanomaterials, which was used to provide improved understanding regarding Cu nanomaterial catalysts under CO2 reduction conditions.

Mapping Heterogeneity of Pristine and Aged Li- and N-Mnhcf Cathode by Synchrotron-Based Energy-Dependent Full Field Transmission X-ray Microscopy.

Manganese hexacyanoferrate is a promising cathode material for lithium and sodium ion batteries, however, it suffers of capacity fading during the cycling process. To access the structural and functional characteristics at the nanometer scale, fresh and cycled electrodes are extracted and investigated by transmission soft X-ray microscopy, which allows chemical characterization with spatial resolution from position-dependent x-ray spectra at the Mn L-, Fe L- and N K-edges. Furthermore, soft X-rays prove to show superior sensitivity toward Fe, compare to hard X-rays. Inhomogeneities within the samples are identified, increasing in the aged electrodes, more dramatically in the Li-ion system, which explains the poorer cycle life as Li-ion cathode material. Local spectra, revealing different oxidation states over the sample with strong correlation between the Fe L-edge, Mn L-edge, and N K-edge, imply a coupling between redox centers and an electron delocalization over the host framework.

Scanning transmission soft X-ray spectromicroscopy of mouse kidney and liver

Scanning transmission X-ray microscopy (STXM) in the soft X-ray range is well-suited to study ultrastructural features of mammalian soft tissues. Especially at the carbon 1s edge, the imaging contrast varies drastically across the edge due to rapid changes in the X-ray absorption cross-section of functional groups present in the tissue samples enabling label-free soft X-ray spectromicroscopic studies. We present STXM spectromicroscopic imaging of mouse kidney and liver tissues. We especially concentrate on ultrastructural abnormalities in genetically modified Slc17a5 mice. STXM is a promising technique to study storage diseases without chemical alteration due to staining agents, but sample preparation poses a challenge.

Ionic liquid functionalized tin halide perovskite investigated by STXM and spectro-ptychography

The structural and compositional properties of tin halide perovskites (CH(NH2)2SnI3, FASnI3) with and without an ionic liquid of 1-Ethyl-3-methylimidazolium bis(trifluormethylsulfonyl) imide (EMITFSI) were investigated using the scanning transmission soft X-ray microscopy (STXM) and spectro-ptychography techniques at the Sn M5,4-edge, I M5,4-edge, O K-edge, C K-edge, and N K-edge. The study offers a comprehensive interpretation of the spectral characteristics of main components (C, N, Sn, and I) in Sn-based perovskites through STXM-based techniques and further reveals differences between the perovskite samples with and without adding EMITFSI ionic liquid. The chemical imaging of Sn and I shows that the perovskite sample without ionic liquid has Sn-rich regions in iodine cavities, while the ionic liquid-treated sample exhibits a more homogeneous perovskite phase. Furthermore, the C and N K-edge XANES resonance features support the interaction between the non-volatile ionic liquid and FA+, thus playing a protective role in the formation and stabilization of perovskite phase.

(Digital Presentation) Post Mortem Microscopical and Selective Analysis of Manganese Hexacyanoferrate Cathode Material By Transmission Soft X-Ray Microscopy

Prussian Blue (PB) and its analogues (PBAs) are a large family of transition metal hexacyanoferrates with general formula of AxM[Fe(CN)6]γ□1-γ∙zH2O. They have open framework structure, redox-active sites and strong structural stability, which makes them perspective electrode materials, as PBAs are able to perform the rapid insertion and extraction of the ions with the lowest possible lattice strain. In addition, they are safe, non-toxic and relatively inexpensive. Among simple PBAs, manganese hexacyanoferrate (MnHCF) displays a high specific capacity and redox plateaus at a high voltage against lithium and sodium in LIBs and SIBs [1]. The synthesis of MnHCF is possible by simple co-precipitation method. In our group we synthesized and investigated its structure and electrochemical performance as a cathode material. For the characterization of MnHCF several conventional and synchrotron-based techniques were used.Generally, after cycling inside the battery some changes might occur in the cathode material, including changing the charge states of the different elements. For the investigation of this phenomenon synchrotron techniques are particularly informative, such as energy-dependent full field transmission soft X-ray microscopy (TXM), which is able to give a full picture at the nanometre scale of the chemical state and spatial distribution of the elements [2]. By using X‐rays in the “soft” energy region (<3 KeV), it is possible to access transitions from the core levels of the light elements, such as the K‐edge of nitrogen, oxygen, fluorine, as well as L- and M- edges of heavier elements [3, 4]. TXM provides pixel-by-pixel absorption spectrum, making it possible to select groups of pixels and map regions with the similar spectral features [2]. Therefore, TXM studies were conducted on our material before and after cycling, and the special protocol of the data treatment was developed and applied to the results of the analysis in order to enhance the representation of the heterogeneities, if any, and then to extract the most relevant spectra.Indeed, the inhomogeneities within the samples were identified, especially in the aged electrodes. It was observed that the distribution of the heterogeneities were different for the electrodes extracted from the Li-ion system, compared to Na. Characteristic spectra from the entire samples as well as particular regions with different oxidation states were obtained and compared to one another, which made it evident, that the treated results from the iron L-edge and manganese L-edge expressed strong correlation, however, while in the Fe K-edge the distribution of heterogeneities looked quite random, a weak bulk-border effect was observed in case of the Mn K-edge.[1] A. Mullaliu, J. Asenbauer, G. Aquilanti, S. Passerini, M. Giorgetti, Small Methods 4, (2019) 1900529.[2] A. Sorrentino, L. Simonelli, A. Kazzazi, N. Laszczynski, A. Birrozzi, A. Mullaliu, E. Pereiro, S. Passerini, M. Giorgetti, D. Tonti, Appl. Sci., no. 11, p. 2791, 2021.[3] D. Tonti, M. Olivares-Marín, A. Sorrentino, E. Pereiro, L. P. Mehdi Khodaei, Ed., IntechOpen, 22 March, 2017.[1] A. Mullaliu, J. Asenbauer, G. Aquilanti, S. Passerini, M. Giorgetti, Small Methods 4, (2019) 1900529.[2] A. Sorrentino, L. Simonelli, A. Kazzazi, N. Laszczynski, A. Birrozzi, A. Mullaliu, E. Pereiro, S. Passerini, M. Giorgetti, D. Tonti, Appl. Sci., no. 11, p. 2791, 2021.[4] D. Attwood, Cambridge: Cambridge University Press, 1999. Figure 1

Angular Characteristics of Soft X-Ray Transmission by Track Membranes with Large Pores

Angular Characteristics of Soft X-Ray Transmission by Track Membranes with Large Pores

Evaluation of the thermal stability of TiW/Cu heterojunctions using a combined SXPS and HAXPES approach

Power semiconductor device architectures require the inclusion of a diffusion barrier to suppress or at best prevent the interdiffusion between the copper metallization interconnects and the surrounding silicon substructure. The binary pseudo-alloy of titanium–tungsten (TiW), with &amp;gt;70 at. % W, is a well-established copper diffusion barrier but is prone to degradation via the out-diffusion of titanium when exposed to high temperatures (≥400 °C). Here, the thermal stability of physical vapor deposited TiW/Cu bilayer thin films in Si/SiO2(50 nm)/TiW(300 nm)/Cu(25 nm) stacks were characterized in response to annealing at 400 °C for 0.5 h and 5 h, using a combination of soft and hard x-ray photoelectron spectroscopy and transmission electron microscopy. Results show that annealing promoted the segregation of titanium out of the TiW and interdiffusion into the copper metallization. Titanium was shown to be driven toward the free copper surface, accumulating there and forming a titanium oxide overlayer upon exposure to air. Annealing for longer timescales promoted a greater out-diffusion of titanium and a thicker oxide layer to grow on the copper surface. However, interface measurements suggest that the diffusion is not significant enough to compromise the barrier integrity, and the TiW/Cu interface remains stable even after 5 h of annealing.

Highly stable surface and structural origin for lithium-rich layered oxide cathode materials

Surface/interfacial engineering is critical for preventing particle degradation of Li-rich layered oxides (LLOs), particularly facet degradation, thereby optimizing their electrochemical performance. Thus, the current study details the investigative analysis of the surface structure of an LLO, followed by its surface engineering. The surface structure was analyzed using scanning transmission electron microscopy (STEM) and soft X-ray absorption spectroscopy (sXAS), and the electrochemical performance was evaluated. The results indicate that an integrated spinel/rock salt (ISR) surface structure formed on the surface in situ. More precisely, the spinel phase originated from the C2/m surface, whereas the rock salt phase originated from the R3m surface, which significantly increased the cycle stability and suppressed voltage decay. After 2000 cycles, the surface-modified LLO cathode retained an extremely high capacity of 69.6% and a low discharge medium voltage with a decay rate of 0.44 mV cycle−1. Additionally, the structural and morphological changes observed after prolonged cycling confirmed the stability of the surface layer. The outstanding performance was attributed to the ultra-stable ISR surface layer, the presence of multiple ion conductivities (LiPO3 and Li2SO4), and the substantial prevention of electrochemical facet degradation. The findings, therefore, highly suggest that the ISR surface concept and the method for surface modification is highly likely to aid in the rapid commercialization of LLOs for battery applications.

Accessing the solid electrolyte interphase on silicon anodes for lithium-ion batteries in-situ through transmission soft X-ray absorption spectroscopy

Silicon offers nine times higher theoretical storage capacity than commercial graphite anodes for Li-ion batteries. For cycling stability, the electrolyte needs to be kinetically stabilized by the so-called Solid Electrolyte Interphase (SEI), a layer which ideally forms once from decomposition products of the electrolyte. While it works for graphite, the SEI on silicon fails to stabilize the electrolyte sufficiently, partly due to the large volume changes upon de-/lithiation. To investigate the SEI on silicon anodes, we developed a novel approach for X-ray Absorption Spectroscopy (XAS), that puts a twist to conventional SiNx window-based liquid cells by utilizing a deliberately induced gas-bubble to form a soft X-ray transparent electrolyte layer. We demonstrate our approach to allow transmission XAS in the soft X-ray regime on liquids and electrode thin-film materials under in-situ conditions. In our case XAS study of the SEI on silicon anodes, we reveal the main SEI constituents as Li acetate, Li ethylene di-carbonate or Li ethylene mono-carbonate, Li acetylacetonate, LiOH, and LiF. Additionally, we see evidence for aldehyde species which we attribute to possible liquid inclusions within a porous SEI morphology. We consider our method an appropriate tool for the successful engineering of a stable, efficient SEI in the future.

Моделирование сильно фотоионизованной плазмы кремния

The work demonstrates the process of simulation a strongly photoionized silicon plasma with parameters close to astrophysical. The calculations were carried out within the model of collisional-radiative equilibrium. The obtained results were verified by comparison with the results of other participants of the codes comparison workshop. A comparative analysis of the results with the experimentally measured spectrum of soft X-ray transmission through a layer of photoionized silicon plasma is carried out.

Magnetic anisotropy in permalloy antidot square lattice

Magnetic anisotropy of Permalloy (Py) antidot square lattice was investigated by torquemetry method using Rotation Magneto-Optic Kerr Effect (ROTMOKE). We find that there exists a field-dependent 4-fold magnetic anisotropy with the easy magnetization axis along the [11] axis of the antidot square lattice. In addition, there also exists an artifact of a uniaxial magnetic anisotropy in ROTMOKE result. We show that both results are due to the period wiggling of the magnetization in space which was confirmed by magnetic imaging using magnetic transmission soft x-ray microscopy (MTXM). Micromagnetic simulation from MuMax3 supports the wiggling structure of the magnetization, as well as reproduces ROTMOKE result. A simplified model was developed based on the periodic wiggling of the magnetization and successfully explored the physical origin of the field-dependent 4-fold anisotropy and the artifact of the uniaxial anisotropy.

X-ray Microspectroscopy and Ptychography on Nanoscale Structures in Rock Varnish

X-ray microspectroscopy is a powerful analytical method in geoscientific and environmental research as it provides a unique combination of nanoscale imaging with high spectroscopic sensitivity at relatively low beam-related sample damage. In this study, “classical” scanning transmission soft X-ray microscopy (STXM) with X-ray absorption spectroscopy and the recently established soft X-ray ptychography are applied to the analysis of selected rock varnish samples from urban and arid desert environments. X-ray ptychography enhances the spatial resolution relative to STXM by up to 1 order of magnitude. With its high chemical sensitivity, it can resolve nanoscale differences in valence states of the key varnish elements manganese (Mn) and iron. Our results emphasize the complex nanoarchitecture of rock varnish as well as the diverse mineralogy of the Mn oxy–hydroxide matrix and its embedded dust grains. In contrast to the fast-growing urban varnish, the slow-growing arid desert varnish revealed a remarkable nanoscale stratification of alternating Mn valence states, providing hints on the layer-wise and still enigmatic growth process.