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2026-01-27: New publication in Acta Materialia: Direct observation of nanoscale pinning centers in Ce(Co0.8Cu0.2)5.4 permanent magnets
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We are pleased to announce our recent publication within the framework of CRC/TRR20. In this joint study, we investigate Ce(Co1-xCux)5 permanent magnets using a correlative approach combining transmission electron microscopy (TEM) and atom probe tomography (APT). The analysis reveals a nanoscale cellular structure formed by spinodal decomposition.
Cu-poor cylindrical cells (∼5-10 nm in diameter and ∼20 nm in length) exhibit a disordered CeCo5-type structure with a composition close to Ce(Co0.9Cu0.1)5.3. These cells are separated by Cu-rich boundaries ∼5 nm thick, characterized by a modified CeCo5 structure with Cu ordering on Co sites and a composition of Ce(Co0.7Cu0.3)5.0. Micromagnetic simulations show that intrinsic Cu concentration gradients of up to 12 at.% Cu per nanometer induce strong spatial variations in magnetocrystalline anisotropy and domain-wall energy, leading to effective domain-wall pinning and high coercivity.
Compared to Sm2Co17-type magnets, Ce(Co0.8Cu0.2)5.4 exhibits a finer-scale pinning mechanism with reduced structural and chemical contrast. The identification of nanoscale chemical segregation in this nearly single-phase system provides a microstructural explanation for the long-standing phenomenon of “giant intrinsic magnetic hardness” in SmCo5-xMx-type materials and highlights new pathways toward the design of rare-earth-lean permanent magnets through controlled nanoscale segregation.
Follow this link for more information: https://doi.org/10.1016/j.actamat.2026.121906.
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2026-01-16: New insights into vibrational properties of 2D Materials
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Scientists from Grenoble, Bordeaux and the University of Duisburg-Essen have unlocked fresh understanding of two-dimensional material that could shape tomorrow's high-performance devices. They have synthesized high-quality Ti3C2Cl2 MXenes, an atomically thin metal carbide with chlorine surface groups, and used cutting-edge techniques to peer deep into how its atoms vibrate and conduct heat.
How lattice vibrations, tiny quantum mechanical ripples called phonons, move through 2D crystals differ from well-explored 3D materials. These vibrations influence everything from thermal conductivity to electrical behavior, but until now, scientists have struggled to measure them accurately in MXenes because of stacking disorder and non-uniform surface terminations.
By carefully growing MXene sheets with uniform chlorine terminations, the team captured exceptionally clear vibrational “fingerprints” using polarized Raman spectroscopy and combined these measurements with theoretical calculations. This revealed how different vibrational modes behave and how they change with temperature giving an unprecedented picture of optical phonon behavior in this 2D material.
In parallel, precise measurements of specific heat and corresponding calculations exposed how MXenes' heat capacity responds to temperature, uncovering tell-tale signs of their two-dimensional character at very low temperatures which is often hidden in other materials.
Understanding and controlling phonons in MXenes is a key step toward designing faster electronics, better thermoelectric materials, and improved energy-storage systems. This work lays solid scientific groundwork for tuning thermal and vibrational properties in 2D materials, bringing next-generation technologies a step closer.
The authors acknowledge financial support of the Deutsche Forschungsgemeinschaft and the Agence Nationale de la Recherche in the bilateral ANR-DFG project.
Reference:
M. Riabov, M. Vanselow, A. Champagne, et al. Phonon properties of 2D Ti3C2Cl2 MXenes. npj 2D Mater Appl 9, 114 (2025).
https://doi.org/10.1038/s41699-025-00625-6
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2025-12-24: Acknowledgement of M. Farle
Prof. Farle has been ranked by ScholarGPS.com as No 4 worldwide in the category of magnetic anisotropy. This result is based on a “revolutionary AI-driven search experience ... ScholarGPS celebrates Highly Ranked ScholarsTM for their exceptional performance in various Fields, Disciplines, and Specialties.” According to AI the scholarly contributions of Prof. Farle have placed him in the top 0.05 % of all scholars worldwide in listing of 2025 ScholarGPS. It is based on an AI analysis over his lifetime career: Highly Ranked Scholar - Lifetime.
You can also view the profile of University of Duisburg-Essen to discover other Highly Ranked Scholars as well as the rankings in various Fields, Disciplines, and Specialties.
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2025-11-21: New publication in Acta Materialia: Tailoring structure, morphology, composition, and magnetism by Ag addition to CoCrFeMnNi–Agx (x = 0; 1; 2.5; 5.5 at. %) high-entropy alloy powders prepared by high-energy ball milling
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We have successfully synthesized nanocrystalline high-entropy alloy (HEA) powders for the first time through a rapid, two-step high-energy ball-milling (HEBM) process in Ar. A single-phase fcc Cantor alloy with uniform elemental distribution was obtained after just 60 min of HEBM from an elemental powder blend. Subsequent HEBM for 10 min with Ag addition enabled precise control over Ag distribution and particle morphology, which evolved from flake-like structures with Ag-rich edges (x = 1; 2.5 at. %) to homogeneous spherical particles (x = 5.5 at. %). All compositions exhibit paramagnetic behavior at 310 K, with Curie temperatures (Tc) decreasing from 96 K (Ag-free CoCrFeMnNi) to 71 K (Ag = 5.5 at. %), indicating suppression of magnetic ordering. Importantly, annealing up to 710 K in a magnetic field significantly enhances the magnetic response across all compositions. The CoCrFeMnNi–Agx (x = 2.5 at. %) HEA shows the most pronounced improvement, with magnetization (M) (9 T, 310 K) increasing 2.5-fold to 16 Am2/kg, coercivity (Hc) reaching 46 kA/m, and remanence of 4.8 Am2/kg. Notably, M approaches ∼ 1/3 of pure Ni under the same conditions, while exhibiting a Hc nearly two orders of magnitude higher.
These results highlight that Ag alloying and thermal treatment offer an effective approach to tuning magnetic properties in CoCrFeMnNi-based HEAs without compromising structural integrity. The ability to tailor structure, morphology, and magnetism through a scalable route promotes Ag-doped Cantor alloys as promising candidates for multifunctional applications requiring combined structural and magnetic performance.
https://doi.org/10.1016/j.actamat.2025.121717
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2025-11-04: Iron-cementite (Fe-Fe3C) "core-shell" magnetic nanoparticles
In a German, United states, Russian and Armenian collaboration 20 nm sized particles embedded in a carbon matrix were synthesized via solid-state pyrolysis of ferrocene and structurally and magnetically characterized. The efficacy of magnetic hyperthermia as a function of nanoparticle concentration, as well as the frequency and amplitude of the alternating magnetic field, was systematically investigated. A numerical model simulating a single nanoparticle embedded in a fluid enabled the determination of the critical concentration in suspensions, beyond which the assumption of non-interacting particles no longer holds. For further details see
https://doi.org/10.1016/j.nxmate.2025.101398 |
2025-10-05: New publication: Tunable Magnetic Remanence of Antiferromagnetically Coupled Fe3O4@SiO2 Nanoparticles for In Vivo Biomedical Applications
In our recent publication "Tunable Magnetic Remanence of Antiferromagnetically Coupled Fe3O4@SiO2 Nanoparticles for In Vivo Biomedical Applications" together with the group of V. Salguerino (U. Vigo, Spain) we investigated the complex switching behavior of two ferromagnetic half-ellipsoids separated by a paramagnetic grain boundary. These particles provide an avenue for biomedical applications in hyperthermia or magneto-mechanic cell destruction. Furthermore, they serve as a prototype study for the magnetic response of two ferromagnetic grains acted on by magnetic fields of different orientation and strengths in a permanent magnet. Our study combining experimental 3D magnetic contrast (Transmission electron Microscopy) and micromagnetic simulations (µMax3) provides quantitative calculations and experimental observations of the remanent magnetization dependent on the sequence of applied magnetic fields -allowing to set a zero or maximum remanent magnetic state of the two grains non-invasively.
https://doi.org/10.1021/acsanm.5c02458 |
