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2020-11-10: Neue AG Mitglieder
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Wir freuen uns, Frau Kübra Yildiz Aktas und Herrn Ali Can Aktas begrüen zu können, die im Rahmen eines Stipendiums des CRC/TRR 270 "Hommage" in den Projekten B09 und A04 an Shell ferromagnetic materials: Tuning the magnetic hysteresis by nanoscale selective phase decomposition und "Hierachical structuring of magnetocaloric materials with nanometer resolution" forschen werden.
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2020-10-07: DAAD funded research stay of scientists from Russia
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We welcome in our group Dr. Natalia Shkodich (Merzhanov Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences) and Dr. Mikhail Cherkasskii (Saint Petersburg State University) who recently joined us for a 3 months research stay funded by DAAD scholarships ("Research stays for University Academics and Scientists, 2020" and "Dmitrij Mendeleev" Program).
Dr. Natalia Shkodich is an expert on combining High-Energy Ball Milling (HEBM) and Spark Plasma Sintering (SPS) to produce nanostructured and amorphous materials from immiscible metals (so-called pseudo alloys), metallic glasses, and high-entropy alloys (HEAs). She aims at producing novel nanostructured CoCrFeNiGa magnetic high entropy alloy (Mag HEA) particles and volume MagHEA materials with a large magnetization, high Curie temperature and tuneable coercivity as well as excellent mechanical properties.
Interests of Assoc. Prof. Dr. Mikhail Cherkasskii are focused on the understanding of magnetization nutation in ferromagnets and its coupling to precession and ferromagnetic resonance. He is working on the development of an analytical approach to describe inertial spin dynamics, nutation resonance and collective excitations in ferromagnets.
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2020-09-15: Auszeichnung für Priv.-Doz. Dr. Ulf Wiedwald und Kollegen
Mageschneiderte Winzlinge gegen den Krebs
Ihre Nanopartikel aus Gold und Magnetit haben sie speziell für die Diagnose und Therapie von Tumoren entwickelt: Physiker vom Center for Nanointegration (CENIDE) der Universität Duisburg-Essen (UDE) und Moskauer Kollegen werden am 15. September für ihre erfolgreiche Zusammenarbeit ausgezeichnet (CENIDE: News). |
2020-07-24: New publication in AIP Advances - Editor's Pick!
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Reversal of uniaxial magnetic anisotropy in Fe/GaAs (110) films driven by surface relaxation: An in situ ferromagnetic resonance study by Babli Bhagat et al.
Performing in situ studies of ferromagnetic resonance in thin metallic films in ultrahigh vacuum, we found a dramatic change of in-plane magnetic anisotropy in 4 nm Fe film grown on GaAs(110) substrate occurring after deposition. Initially grown, Fe/GaAs(110) film exhibits unusual uniaxial in-plane anisotropy which reverses its sign within 40 hours while the film is kept in vacuum at room temperature. The effect of surface contamination has been excluded using surface-sensitive techniques AES and LEED, which let us to conclude on metastability and ongoing surface relaxation of Fe film. This finding opens up a further study of such island-like grown metastable thin films where magneto-morphological transitions can be altered by temperature and other external stimuli.
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2020-03-10: Non-standing spin-waves in confined micrometer-sized ferromagnetic structures under uniform excitation
Editors Pick (!)
Non-standing spin-waves in confined micrometer-sized ferromagnetic structures under uniform excitation
Appl. Phys. Lett. 116, 072401 (2020); https://doi.org/10.1063/1.5139881
Santa Pile et al.
A long effort within an international collaboration (U. Linz, Duisburg-Essen, Stanford) including partners from the CRC/TRR 270 broke new ground in element-specific magnetic imaging with picosecond temporal and few nanometer spatial resolution. A non-standing characteristic of directly imaged spin-waves in confined micrometer-sized ultrathin Permalloy (Ni80Fe20) structures is reported along with evidence of the possibility to alter the observed state by modifications to the sample geometry. |
2020-03-10: Dynamic unidirectional anisotropy in cubic FeGe with antisymmetric spin-spin-coupling
Nicolas Josten, et al. Scientific Reports 10, 2861, (2020)
DOI: 10.1038/s41598-020-59208-8
Successful collaboration with TU-Darmstadt within CRC/TRR 270. We studied bulk polycrystalline B20 FeGe samples prepared in Darmstadt and measured ferromagnetic resonance spectroscopy. As a result we discovered strong (dynamical) unidirectional anisotropy. Such anisotropy is not present in static magnetometry measurements. B20 FeGe exhibits inherent Dzyaloshinskii-Moriya interaction, resulting in a nonreciprocal spin-wave dispersion. By X-band ferromagnetic resonance spectroscopy at 276 K 1 K, near the Curie temperature, a distribution of resonance modes was observed in accordance with the cubic anisotropy of FeGe. This distribution exhibits a unidirectional anisotropy, i.e. shift of the resonance field under field inversion, of KUD = 960 J/m3 10 J/m3, previously unknown in bulk ferromagnets. Additionally, more than 25 small amplitude standing spin wave modes were observed inside a micron sized FeGe wedge, measured at 293 K 2 K. These modes also exhibit unidirectional anisotropy. This effect, only dynamically measurable and not detectable in static magnetometry measurements, may open new possibilities for directed spin transport in chiral magnetic systems. |
2020-01-17: Highlighted Publication
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The publication based on our long term collaboration with the group of Vernica Salgueirio (university of Vigo, Spain) Shaping iron oxide nanocrystals for magnetic separation applications has been selected to be a part of a themed collection International Year of the Periodic Table: As attractive as magnets applications for magnetic materials. This themed collection is the seventh, and final, in a series celebrating the International Year of the Periodic Table. As Attractive as Magnets Applications for Magnetic Materials features papers from across the Materials and Nano journal portfolio; Materials Horizons, Nanoscale Horizons, Nanoscale, Nanoscale Advances and Journal of Materials Chemistry A, B & C. The papers selected for this themed issue focus on the current hot trends in the field of magnetic materials.
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2020-05-29: Doktorandenstellen
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In unserer Arbeitsgruppe sind Doktorandenstellen zum nächstmäglichen Zeitpunkt zu folgenden Projekten zu besetzen:
B09: "Hierarchical structuring of magnetocaloric materials with nm resolution"
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2019-11-26: Cooperate Research Center TRR 270 HoMMage
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We celebrate the new Cooperate Research Center TRR 270 HoMMage "Hysteresis Design of Magnetic Materials for Efficient Energy Conversion".
Starting Jan 1st, 2020 we will design and develop magnetic materials for applications in electro mobility, robotics and energy converters over the first period till Dec. 31st , 2023.
In our group we have three positions for Ph.D. students available on projects related to this programme (see separate announcements).
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2019-09-26: Workshop SpinS-2019 gathers experts in nanomagnetism at the University of Duisburg-Essen
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Next week, 2-4 October 2019, more than 40 experts in physics, chemistry and materials science from 12 countries meet in “Die Wolfsburg” Academy in Mülheim an der Ruhr/Duisburg to share their research results and discuss new concepts in nanomagnetism and its applications, like energy-efficient computing and magnetic refrigeration.
The Workshop program covers the most recent experimental and theoretical research developments related to spin phenomena in nanoscale systems as well as the design, properties and applications of magnetic nanomaterials. It includes several emergent technologies based on spin-orbit torques, ultrafast spin dynamics in THz frequency range, magnonics, magnetoacoustics as well as novel materials like shell-ferromagnets, MAX phases (including 2D MXenes), and nanohybrids for theranostics applications actively developed in the working group AG Farle. The SpinS-2019 provides an interdisciplinary platform for meeting the specialists in fabrication and imaging of 2D and 3D magnetic nanostructures, and experts working towards various application areas – from spin dynamics and magnetic memory to additive manufacturing and biomedicine.
The meeting is organized by Michael Farle, Katharina Ollefs and Anna Semisalova, with a technical support of Michael Vennemann and Sabina Grubba. Organizers highly appreciate the financial support of the Center for Nanointegration Duisburg-Essen (CENIDE).
SpinS-2019 website
Flyer
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2019-09-26: High Entropy Alloys: How to induce ferromagnetism?
High-entropy alloys are currently the focus of significant attention in materials science and engineering. Some HEAs have considerably better strength-to-weight ratios, with a higher degree of fracture resistance, tensile strength, as well as corrosion and oxidation resistance than conventional alloys. In the recent publication Mehmet Acet showed how to introduce strong magnetism in a Cr20Mn20Fe20Co20Ni20 high-entropy alloy. He could show through the thermal expansion properties that the alloy carries similar anti-Invar properties as FCC-Fe, but unlike FCC-Fe it is stable throughout its solid-state temperature range. Therefore, by exploiting the anti-Invar property and expanding the lattice of the alloy by introducing interstitial carbon, we make Cr20Mn20Fe20Co20Ni20 ferromagnetic with a Curie temperature lying above room temperature.
For details see: https://doi.org/10.1063/1.5120251
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Picture from Von Shaoqing Wang - Wang, Shaoqing (13 December 2013). "Atomic Structure Modeling of Multi-Principal-Element Alloys by the Principle of Maximum Entropy". Entropy 15 (12): 55365548. DOI:10.3390/e15125536., CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=32060405
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