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2024-02-07: Ausschreibung Doktorand*innen oder PostDoc Stelle
Wir haben die Stelle eines wissenschaftlichen Mitarbeitenden TVL 13 ausgeschrieben: . 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.
2023-08-12: 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
2023-07-18: Femtosecond Laser Ablation-Induced Magnetic Phase Transformations in FeRh
In a trilateral French-Spanish-German collaboration we investigated the ablation properties of FeRh films. We found that the initial FeRh film displayed a reversible antiferromagnet-ferromagnet phase transition and the laser-ablated structures exhibited irreversible changes in their magnetic properties. Fluence-resolved measurements clearly demonstrate that the ablation threshold coincides with the threshold of the antiferromagnet-to-ferromagnet phase transition. For details see: Femtosecond Laser Ablation-Induced Magnetic Phase Transformations in FeRh Thin Films .
2023-07-18: Easy up-scalable synthesis for ferrite nanoparticles
In a joint transatlantic effort we analyzed the magnetic and structural character of ferrite nanoparticles. The results are astonishing. For more information , please see One pot, scalable synthesis of hydroxide derived ferrite magnetic nanoparticles .
2023-06-29: Ni-Mn-Sn Heusler alloys manufactured by e-beam and laser powder bed fusion
In a recent joint publication of the CRC/TRR270 we published a comparative study of additive manufacture Ni-Mn-Sn Heusler alloys.
Using an uncommon PBF-EB/M spot melting strategy, for the first time, crack-free Ni-Mn-Sn bulk material were produced and the chemical, microstructural, and magnetic properties were analyzed. Results on the magnetocaloric effect of the consolidated samples are reported. For details see S.-K. Rittinghaus et al. , Additive Manufacturing Letters 7 (2023) 100159 .
2023-06-16: Good Bye Manolis!
After his 5-months ERASMUS-funded internship Emmanouil Kasotakis left us after setting up and testing a now fully functioning sputter deposition system which he commissioned together with Moritz Vanselow and Dr. Anna Semisalova.
We wish him a fruitful and successful career wherever his interest my lead him.
2023-06-13: Towards THz Physics with GHz excitation (inertia in spin dynamics)
The dynamics of magnetic moments consists of a precession around the magnetic field direction and a relaxation towards the field to minimize the energy. While the magnetic moment and the angular momentum are conventionally assumed to be parallel to each other, at ultrafast time scales their directions become separated due to inertial effects. The inertial dynamics gives rise to additional high-frequency modes in the excitation spectrum of magnetic materials. Here, our international collaboration reviews the recent theoretical and experimental advances in this emerging topic and discuss the open challenges and opportunities in the detection and the potential applications of inertial spin dynamics.
For further details see
2023-05-02: We welcome Berna Gündogdu Gültepe!
She completed her master degree at Istanbul University and is now a visiting researcher at the AG Farle team to develop a project until 31 October 2023.
Focusing on Heusler alloys, the project includes the preparation and examination of multilayer thin films prepared by flash evaporation of multi-element materials.