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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 |
2025-09-19: New publication: New Theoretical Framework Sheds Light on High-frequency Magnetic Phenomena Driven by Inertia
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Our research group has developed a new theoretical model that offers a deeper understanding of how magnetic materials behave at extremely high frequencies. Published in the APS journal Physical Review B, our work explains how inertial effects influence the magnetic resonance response of ferromagnets.
Previous models for microwave spectroscopy reached their limits when frequencies became so high that the inertia of magnetic moments came into play. This inertia causes the magnetization to show a delayed response to an applied magnetic field, much like a spinning top that wobbles (nutation) after a nudge before settling back into a stable rotation.
The new framework provides a comprehensive mathematical solution to quantitatively predict these effects. It yields the complete tensor of the magnetic susceptibility, a measure of how a material responds to an external magnetic field. Crucially, our model accounts for both the primary oscillation (precession) of the magnetisation and the subtle, high-frequency nutation that occurs in the terahertz range for continuous microwave excitation.
These findings are particularly relevant for magnonics, a field that uses spin waves to transmit and process information. By paving the way for new magnonic components operating in the terahertz range, this research could be the foundation for the next generation of ultra-fast, energy-efficient data processing.
https://doi.org/10.1103/dhk6-78tt
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2025-09-04: New CRC/TRR 270 HoMMage Publication: Nanocrystalline Room-Temperature Ferromagnetic CoCrFeNiGa High-Entropy Alloy with Potential Breakthrough for Spintronic Devices
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We are delighted to announce our recent publication in ACS Nano in collaboration with Prof. Hari Srikanth and his group at the University of South Florida.
In this work, we report on nanocrystalline CoCrFeNiGa, a room-temperature bulk magnetic high-entropy alloy (HEA) based on 3d transition metals. The alloy exhibits mixed BCC–FCC phases with ~51 nm crystallites, a high Curie temperature of ~872 K, soft magnetic behavior, and spin freezing below 60 K.
Most notably, CoCrFeNiGa demonstrates a large intrinsic anomalous Hall effect (AHE) — ~603 S⋅cm-1 at 5 K and ~144 S⋅cm-1 at 300 K — making it highly promising for next-generation spintronic devices.
This study highlights nanocrystalline magnetic HEAs as robust candidates for applications under demanding conditions, opening exciting avenues for spintronic architectures.
For details see here
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2025-08-08: Invited talks at Magnonics 2025 (Spain) and Spintronics XVIII (SPIE Optics + Photonics 2025, USA)
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Our group members gave invited talks at international conferences Magnonics 2025, Spain (Anna Semisalova) and Spintronics XVIII, SPIE Optics + Photonics, Nanoscience + Engineering Symposium, USA (Jonas Wiemeler). |
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2025-07-18: New CRC/TRR 270 HoMMage publication: Nanocrystalline CoMnFeNiGa high entropy alloys: Room temperature ferromagnetism bridging the gap from Bulk to Nano
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This study demonstrates a scalable and unique processing strategy for tailoring the structure, microstructure and magnetic properties of CoMnFeNiGa HEAs across different length scales — micropowder, bulk, and NPs. The high energy ball milling (HEBM) enables the incorporation of low-melting Ga into a stable, single-phase FCC nanocrystalline HEA matrix. Subsequent spark plasma sintering (SPS) induces partial FCC→BCC transformation and nanoscale compositional segregation, producing dual-phase HEA bulk with enhanced magnetic performance. Microparticle laser fragmentation in liquid (MP-LFL) emerges as a robust synthesis platform for producing compositionally complex NPs in a single step directly from the HEBM microparticles. Metal-liquid interactions critically determine the NP morphology (spheres and platelets) and subsequent phase structure, offering promising avenues for solvent-dependent phase control while retaining multi-elemental stoichiometry. Despite structural complexity, all forms exhibit RT ferromagnetism, with magnetic behavior governed by processing-induced variations in phase composition, crystallite size, and microstrain. A rapid thermal treatment (30 s) at 1000 K led to significant improvements in magnetic properties across all forms, driven by phase transformations and microstructural modification. This study provides a new pathway to engineer soft ferromagnetic HEAs with tailored properties by controlling phase composition, crystallite size, nanoscale chemical segregation, and processing-induced microstructure through synthesis and subsequent heat treatment.
For details see here.
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