Eldorado - Repositorium der TU Dortmund

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Aktuellste Veröffentlichungen

Spin‐selective interface engineering in oxide–ferromagnetic junctions via atomic‐scale oxygen control
(2026-02-20) Janas, David Maximilian; Arndt, Mira Sophie; Nitschke, Jonah Elias; Sternemann, Lasse; Mischke, Valentin; Feyer, Vitaliy; Cojocariu, Iulia; Baranowski, Daniel; Sala, Alessandro; Windischbacher, Andreas; Puschnig, Peter; Dreiser, Jan; Ponzoni, Stefano; Zamborlini, Giovanni; Cinchetti, Mirko
Atomic-scale control of oxide–ferromagnet interfaces is crucial for optimizing spintronic heterostructures, yet interfacial oxygen remains difficult to control and verify. Here, we deterministically tune the prototypical MgO/Fe(100) interface from oxygen-free terminations to fully intercalated oxygen layers by reactive growth under controlled O2 exposure, while preserving epitaxy. Momentum-resolved photoemission identifies oxygen-dependent fingerprints in k-space that originate from the buried interface and persist up to a thickness of 8 layers of MgO. Insights from complementary spectroscopic methods link these k-space signatures to interfacial chemistry, structural order, work-function shifts, and an oxygen-induced interface resonance within the MgO gap that alters the tunneling response. The combined results define a calibrated growth protocol that allows reproducibly preparing and identifying three distinct terminations — oxygen-free, partially oxidized, and oxygen-intercalated — and enables post-growth conversion even in thicker films. Complementary spin-resolved experiments reveal that oxygen-free interfaces exhibit pronounced suppression of minority-spin spectral weight at the Fermi level, consistent with coherent spin filtering across crystalline MgO, whereas oxygen intercalation reduces the spin contrast at EF. By turning interfacial oxygen from an uncontrolled variable into a measurable, adjustable parameter, our approach establishes MgO/Fe(100) as a benchmark platform for optimizing spintronic functionality in oxide/metal junctions.
Electronic structure reorganization in MPS3 via d‐shell‐selective alkali metal doping
(2026-03-24) Nitschke, Jonah Elias; Bhumla, Preeti; Willershausen, Till; Merisescu, Patrick; Janas, David Maximilian; Sternemann, Lasse; Gutnikov, Michael; Schiller, Karl; Mischke, Valentin; Capra, Michele; Arndt, Mira Sophie; Botti, Silvana; Cinchetti, Mirko
Semiconducting two-dimensional (2D) antiferromagnetic (AFM) transition-metal thiophosphates (MPS3) offer promising opportunities for spintronic applications due to their highly tunable electronic properties. While alloying and intercalation have been shown to modulate ground states, the role of d-shell filling in governing these transitions remains insufficiently understood. Here, we investigate electron doping effects in MPS3 using angle-resolved photoemission spectroscopy (ARPES), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT+U). Lithium and cesium deposition are employed to induce doping across different MPS3 compounds. We identify two distinct doping mechanisms: in MnPS3, electrons are primarily donated to the P2S6 ligand clusters, with negligible Mn 2p core-level shifts and no major changes in the valence band. In contrast, FePS3, CoPS3, and NiPS3 exhibit clear reductions in transition-metal oxidation states, with a ∼1.0 eV reduction in spin-orbit splitting for Co upon doping. ARPES on CoPS3 reveals a ∼400 meV shift of Co-derived bands toward higher binding energies and new dispersive states up to 1 eV above the valence band maximum, indicating metallic behavior. These results establish a direct correlation between d-shell filling and doping response, highlighting alkali metal doping as a tunable route to tailor the electronic and magnetic properties of 2D AFM semiconductors for spintronic applications.
A robust test for equal predictive accuracy
(2026) Demetrescu, Matei; Hanck, Christoph; Hoga, Yannick
This paper studies what we call a "robust" Diebold–Mariano type test. The unique feature of our test is that - even in the absence of any knowledge of the forecasting method - it is robust to estimation noise in the forecasts, i.e., size is kept irrespective of estimation effects induced by model fitting. We obtain this feature by a test statistic that is based on rolling-window means whose length is a vanishing fraction of the total evaluation sample. This leads to non-standard Gumbel limit laws. Other desirable features of our test are that it is easily robustified against time-varying volatility, and that it naturally uncovers time-varying differences in predictive ability under the alternative. Simulations demonstrate the benefits of our multiply robust implementation vis-à-vis several competitors. An empirical application to forecasts for several variables, horizons, vintages and methods from the Survey of Professional Forecasters illustrates the relevance of the new approach, allowing us to identify forecasters with superior models. Such conclusions are in fact impossible to infer by extant tests, since information on the models and estimation procedures behind the forecasts are typically proprietary and, hence, estimation effects cannot be factored out.
(Food) justice in the interim? Temporary urban gardening, welfare activation, and plural valuation
(2026-06-01) Bakunowitsch, Julija
Across European cities, temporary urban gardening is used to address vacancy, sustainability, and social inclusion. Yet little is known about how justice is enacted when such initiatives are embedded in welfare and labor‐market activation policies. This article examines a publicly funded urban gardening project in Dortmund, Germany, implemented as a labor‐market activation measure on temporarily available land targeting employable welfare recipients. Drawing on qualitative data from interviews, participant observation, and document analysis, the study combines the concept of “food justice” with valuation studies to analyze how labor, land, and exchange are valued in everyday practice. Rather than using food justice as a normative benchmark, the article explores how notions of justice are produced and negotiated through institutional frameworks, daily routines, and actors’ evaluative judgments. The findings reveal tensions between empowerment and dependency, care and control, and social recognition and material precarity. While participants experience gardening as meaningful work and a source of social participation and belonging, these valuations remain bounded by welfare regulations, temporary land tenure, and charity‐based forms of food distribution. The article argues that temporary urban gardening projects function as spaces of plural and negotiated valuation, where justice is enacted provisionally through everyday practices, contributing to debates on temporary urban land use, food practices under welfare governance, and the limits of inclusion‐oriented sustainability interventions.
Integrating artificial intelligence in investigating magneto-bioconvection flow of oxytactic microorganisms and nano-enhanced phase change material in H-type cavity
(2024-03-01) Hussain, Shafqat; Aly, Abdelraheem M.; Alsedias, Noura; Çolak, Andaç Batur
Nano-enhanced phase change materials is an effective way to improve the thermal characteristics and to minimize energy consumption. The bioconvection flow of nano-enhanced phase change materials is gaining more attention in recent investigations due to its significant applications in engineering and medical sciences. The present study aims to numerically explore magneto-bioconvection flow of nano-enhanced phase change materials in H-type cavity including oxytactic microorganisms. The cavity is constantly heated from the left and a right wall is maintained at cold temperature. The major focus of the current investigation is analyzing the flow and thermal features of the suspension of nano-enhanced phase change materials and a host fluid. The governing system is reduced to the dimensionless form by applying the appropriate transformation. Impact of pertinent parameters, porosity, cavity aspect ratio, Darcy, Hartmann, Lewis, Rayleigh, bioconvection Rayleigh numbers, radiation parameter, and Péclet number on bioconvection flow of oxytactic microorganisms in H-type cavity has been analyzed. Six various artificial neural network models are explored in order to estimate critical parameters with an artificial intelligence approach. It is found that the variations of a cavity aspect ratio are enhancing the bioconvection flow and phase change material. Increasing Hartmann number reduces the nanofluid velocity and distributions of oxygen and microorganisms. The Rayleigh and bioconvection Rayleigh numbers are playing an importance role in enhancing bioconvection flow and varying phase change material.As Ha increases from 10 to 100, at γ=900, there is a 1.67% decrease in the values of Nuavg and a 0.247% increase in Shavg. Among the study findings, the developed artificial neural networks can predict each parameter with high accuracy.