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2025-04-24: Magnetic nanoplatelets for biomedical applications
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Magnetic nanoparticles for diagnostic applications require unique magnetic properties and the ability to be manipulated by external magnetic fields. Our collaborative study presents the synthesis of uniform magnetic CoNi nanoplatelets through the topotactic reduction of metal hydroxides. Different state-of-the-art magnetic measurement techniques confirm the formation of ferromagnetic metal platelets with a magnetic vortex-like structure at ambient temperature. Additionally, micromagnetic simulations confirm the formation of magnetic vortex remanent states at diameters between 200 nm and 1 μm and a thickness of 12 nm. Notably, structural defects and thickness variations do not directly destabilize the magnetic vortex configurations. Details can be found in https://doi.org/10.1002/smsc.202500111.
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2025-04-19: Ways to manipulate magnetism in a high entropy alloy
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In a recent collaboration between the groups of Prof.s Zi-An Li and M. Farle we demonstrate how the microstructure influences the soft magnetic and mechanical properties of (MnFeCoNiCu)100-xAlx, (x = 20, 25, 30, 35, 40). The addition of Al promotes a microstructural change from a coexistence of face-centered cubic (FCC), body-centered tetragonal (BCT), and B2 phases to a single B2 phase. The alloys exhibit high saturation magnetization MS = 105.5 Am2/kg at T = 100 K), low coercivity ( = 8.7 A/m), high Curie temperature ( = 732 K), and high Vickers hardness of 513 HV. Details can be read in https://doi.org/10.1016/j.jmrt.2025.04.061.
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2024-12-10: Research stay of Ye Jiang (Tohoku University) in our group
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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.
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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 CoCrFeNiGax (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, Ms = 55 Am2/kg and Tc = 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 CoCrFeNiGax (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.
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2024-12-02: Magnetic hardening of SmCo5: the search for the perfect defect
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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.
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2024-09-20: 820. WE-Heraeus-Seminar
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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. |
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