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AG Farle

Struktur und Magnetismus nanoskaliger Systeme

Willkommen !

Wir begrüßen Sie sehr herzlich auf den Webseiten der Arbeitsgruppe Farle.
Das Verständnis magnetischer Eigenschaften von nanostrukturierten Materialien ist unsere Herausforderung !

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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).

2020-11-10: Neue AG Mitglieder
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.

2020-10-07: DAAD funded research stay of scientists from Russia
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.

2020-07-24: New publication in AIP Advances - Editor's Pick!
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.

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.

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