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AG Farle

Struktur und Magnetismus nanoskaliger Systeme

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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).

2020-07-24: 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.

2020-01-17: Highlighted Publication
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.

2020-05-29: Doktorandenstellen

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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