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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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2024-12-10: Research stay of Ye Jiang (Tohoku University) in our group

We welcome Ye Jiang from the Department of Electrical Engineering, Graduate School of Engineering, Tohoku University in our group! During his 6-months stay Ye will investigate static and dynamic magnetic properties of epitaxial FeSi and FeGe thin films and correlation of damping and magnetostriction.

2024-12-03: New publication in Acta Materialia

Our recent study has successfully demonstrated the one-step synthesis of homogeneous nanocrystalline (~ 10 nm) single-fcc magnetic CoCrFeNiGa_x (x = 0.5; 1) high entropy alloy (HEA) powder particles containing low melting element of Ga through short-term high energy ball milling (HEBM). The results of their thermal stability (up to 1300 K ±5 K) in correlation with their structure, composition and enhancement of magnetic properties during heat treatment, as well as after consolidation by spark plasma sintering (SPS) were investigated including high resolution transmission electron microscopy (HRTEM) and atom probe tomography (APT).
The combination of HEBM and SPS yields homogeneous bulk HEAs with low-melting Ga and enhanced structural, composition, and thermal stability, as well as improved magnetic properties, M_s = 55 Am²/kg and T_c = 750 K, which is 45% and 47 K higher, respectively, compared to conventional melting approaches.

The study was carried out in collaboration with the Max Planck Institute for Sustainable Materials (Düsseldorf, Germany) and Ernst Ruska Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich, (Jülich Germany).

Effect of high energy ball milling, heat treatment and spark plasma sintering on structure, composition, thermal stability and magnetism in CoCrFeNiGa_x (x = 0.5; 1) high entropy alloys
N. F. Shkodich, T. Smoliarova, H. Ali, B. Eggert, Z. Rao, M. Spasova, I. Tarasov, H. Wende, K. Ollefs, B. Gault, M. Farle
Acta Materialia 284 (2025), 120569. DOI: https://doi.org/10.1016/j.actamat.2024.120569.

2024-12-02: Magnetic hardening of SmCo₅: the search for the perfect defect

The CRC/TRR20 „HoMMAge” investigates new ways to enhance the magnetic energy product of high-performance magnets. In our recent publication Hard magnetic SmCo5-Sn nanocomposites produced by high-pressure torsion we demonstrate how High-Pressure Torsion (HPT) processing of SmCo₅ and Sn powder blends produces tailored textures of magnetic SmCo₅-20 wt.% Sn nanocomposites. The use of powders as precursors which are consolidated by the process, overcomes the limitations of conventional sintering based routes, as the hard magnetic phase and the grain boundary phase can be freely selected. Simultaneously, the microstructure can be adjusted by different process parameters.

In this work, Sn is used as binder phase to magnetically decouple the SmCo₅ particles and thus enhance magnetic hardening effects while simultaneously it is not soluble within the SmCo₅ phase, thus preventing or rather delaying mechanical alloying effects. The influence of different number of rotations on the microstructure and the accompanied magnetic properties is discussed in:
https://doi.org/10.1016/j.jallcom.2024.177858.

2024-09-20: 820. WE-Heraeus-Seminar

The application of Jonas Wiemeler for the participation in 820. WE-Heraeus-Seminar "Hybrid Angular Momentum Transport and Dynamics" has been accepted by the organizers.
The seminar will take place on 27-31 October 2024 at the "Physikzentrum Bad Honnef" near Bonn. We are looking forward to Jonas' participation and his impressions on being a part of this renowned seminar.

2024-07-16: Group excursion of AG Farle - summer 2024 edition

We had fun!
Our group visited Zoo Duisburg near University.

2024-07-10: Public lecture by Prof. M. Farle in the framework of "Die Kleine Form"

Public lecture "Magnete als Klimaretter (Materialien für eine emissionsfreie Zukunft)" (German only) by Prof. M. Farle in the framework of "Die Kleine Form" on June 19, 2024. The lecture can be seen and heard here: https://www.uni-due.de/kleine-form/farle.php.

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