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AG Farle

Struktur und Magnetismus nanoskaliger Systeme

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Das Verständnis magnetischer Eigenschaften von nanostrukturierten Materialien ist unsere Herausforderung !

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2024-02-07: Ausschreibung Doktorand*innen oder PostDoc Stelle
Wir haben die Stelle eines wissenschaftlichen Mitarbeitenden TVL 13 ausgeschrieben: https://www.uni-due.de/karriere/stelle.php?kennziffer=086-24 . Es können sich sowohl Personen, die an einer Promotion interessiert sind, als auch promovierte Personen bewerben, die entweder Ihr eigenes Projekt mitbringen und dieses durch eine(n) weiteren Mitarbeiter*in verstärken wollen, oder selber die PostDoc Position annehmen wollen. Die PostDoc Stelle könnte nach zwei Jahren nach positiver Evaluation um weitere zwei Jahre verlängert werden.
2024-02-02: We welcome Emmanouil Kasotakis to our team!
He will work on his PhD thesis within the DFG project titled "Tailoring magnetism of High Entropy Alloys (HEA) by high energy ball milling".
His research will be focused on the development of innovative (soft or hard) magnetic HEA materials with chemical and mechanical robustness.
We wish him success in his research and excellent results!
2024-01-18: "Cellular precipitation in Ni-Mn-Sn revealed", Phys. Rev. Materials 7 (2023) 124411
"Cellular precipitation in Ni-Mn-Sn revealed", Phys. Rev. Materials 7 (2023) 124411 Combining the expertise of 5 participating projects in the SFB/TRR 270 HoMMage the location and morphology of ferromagnetic precipitates in Ni-Mn-Sn was determined. Ni50Mn45Sn05 heated above 600 K decomposes into ferromagnetic Ni2MnSn precipitates in an antiferromagnetic NiMn matrix. If an external magnetic field is applied during annealing, magnetic hysteresis curves with high coercive fields of up to 5 T can be achieved. The origin of this hysteresis has been attributed to the coupling of the antiferromagnetic matrix L10 NiMn with ferromagnetic precipitates (Sn enriched regions), whose location and morphology were not known. To close this knowledge gap, a range of sophisticated experimental techniques – ranging from magnetic force microscopy over transmission electron microscopy to atom probe tomography -was applied aside from conventional magnetometry and x-ray diffraction. The decomposition type is identified as a cellular precipitation starting at grain boundaries and growing into the grains. This leads to a multilayer thin film like lamellar structure with a lamella thickness in the nm range as seen in the attached figure. These results may provide a basis for understanding the magnetic interactions, which lead to the magnetic hysteresis with ultra high coercivity in these types of "shell ferromagnets"

Abb: a) HAADF STEM image of the sample annealed for 24 h at 700 K. The decomposition product of phase I toward Ni2MnSn and NiMn is visible and forms a lamellar structure.
(b) HAADF STEM image of the region marked in (a) (yellow rectangle). The thickness of the Ni2MnSn lamellar precipitates is around 10 nm.
(c) EDX mappings of Ni, Mn, and Sn performed on the area shown in (b).
(d) EDX linescans measured within the yellow rectangles shown in (b). The x-axes of the plots of the linescans follow the yellow arrows.
2023-08-17: GRATULATION: MSc. Nanoeng. Inci Nur Sahin

Die Abbildung zeigt die chemische Zusammensetzung eines typischen Partikels.
Wir freuen uns mit Inci über den Abschluss Ihrer Masterarbeit im Studiengang Nanoengineering. Ihre Arbeit und ihr Abschlusskolloquium wurden mit den jeweils bestmöglichen Noten bewertet. Ihre Forschung zu "Optimierter Hyperthermie Ansatz mittels Fe3O4/SiO2/Ni Multischalen Nanoellipsoiden" demonstriert eine neues Konzept zur biomedizinischen Theranostik mit synthetischen Antiferromagneten, die aus Magnetit Halbschalen in einer Siliziumdioxid Hülle bestehen, naßchemisch herstellbar und hoch-skalierbar sind, sowie ohne magnetische Streufelder in biomedizinischen Anwendungen verwendet werden könnten.
Die Arbeit ist hier zu finden.
2023-08-12: Pinned magnetic moments in the collinear antiferromagnet PdMn
Pinned magnetic moments in the collinear antiferromagnet PdMn In a joint research work within the CRC/TRR270 "Hysteresis design of magnetic materials for efficient energy conversion" Nicolas Josten (PhD candidate) in project A04 could show that annealing the collinear antiferromagnet PdMn with excess Pd in a magnetic field produces strongly pinned magnetic moments in the annealing field direction. This behavior can be understood with the help of the magnetic-field-biased diffusion model. Here, the magnetic field creates an energy difference between the two possible occupations of the antiferromagnetic Mn-sublattices by the Pd-excess atoms. This, mediated by diffusion, leads to an imbalance in the amount of the Pd-excess atoms in these sublattices and, subsequently, to an imbalance in the total magnetization of the sublattices. For Details see: Annealing time, temperature, and field dependence of pinned magnetic moments in the collinear antiferromagnet PdMn
2023-08-09: Helical magnetic structure of epitaxial films of nano-laminated Mn2GaC MAX phase
In a multinational collaboration we could identify a complex magnetic arrangement of Mn magnetic moments, that is a helical magnetic structure consisting of the ferromagnetically coupled Mn-C-Mn slabs that are twisted across the Ga layer by 167.2 deg with respect to the next Mn-C-Mn slab. As a result, the magnetic structure presents a spiral propagating along the out-of-plane direction (hexagonal c axis) with a pitch of around 14 lattice constants. For Details see: Annealing time, temperature, and field dependence of pinned magnetic moments in the collinear antiferromagnet PdMn

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