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  1. Article ; Online: Coherent Magnons with Giant Nonreciprocity at Nanoscale Wavelengths.

    Gallardo, Rodolfo / Weigand, Markus / Schultheiss, Katrin / Kakay, Attila / Mattheis, Roland / Raabe, Jörg / Schütz, Gisela / Deac, Alina / Lindner, Jürgen / Wintz, Sebastian

    ACS nano

    2024  

    Abstract: Nonreciprocal wave propagation arises in systems with broken time-reversal symmetry and is key to the functionality of devices, such as isolators or circulators, in microwave, photonic, and acoustic applications. In magnetic systems, collective wave ... ...

    Abstract Nonreciprocal wave propagation arises in systems with broken time-reversal symmetry and is key to the functionality of devices, such as isolators or circulators, in microwave, photonic, and acoustic applications. In magnetic systems, collective wave excitations known as magnon quasiparticles have so far yielded moderate nonreciprocities, mainly observed by means of incoherent thermal magnon spectra, while their occurrence as coherent spin waves (magnon ensembles with identical phase) is yet to be demonstrated. Here, we report the direct observation of strongly nonreciprocal propagating coherent spin waves in a patterned element of a ferromagnetic bilayer stack with antiparallel magnetic orientations. We use time-resolved scanning transmission X-ray microscopy (TR-STXM) to directly image the layer-collective dynamics of spin waves with wavelengths ranging from 5 μm down to 100 nm emergent at frequencies between 500 MHz and 5 GHz. The experimentally observed nonreciprocity factor of these counter-propagating waves is greater than 10 with respect to both group velocities and specific wavelengths. Our experimental findings are supported by the results from an analytic theory, and their peculiarities are further discussed in terms of caustic spin-wave focusing.
    Language English
    Publishing date 2024-02-05
    Publishing country United States
    Document type Journal Article
    ISSN 1936-086X
    ISSN (online) 1936-086X
    DOI 10.1021/acsnano.3c08390
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Book ; Thesis: Spin vortices in magnetic multilayers

    Wintz, Sebastian

    2014  

    Author's details von Sebastian Wintz
    Language English
    Size IV, 141 S., Ill., graph. Darst.
    Document type Book ; Thesis
    Thesis / German Habilitation thesis Techn. Univ., Diss.--Dresden, 2014
    Database Library catalogue of the German National Library of Science and Technology (TIB), Hannover

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  3. Book ; Online: Direct observation of N\'eel-type skyrmions and domain walls in a ferrimagnetic thin film via scanning transmission X-ray microscopy

    Luo, Chen / Chen, Kai / Ukleev, Victor / Wintz, Sebastian / Weigand, Markus / Prokeš, Karel / Radu, Florin

    2023  

    Abstract: Isolated magnetic skyrmions are stable, topologically protected spin textures that are at the forefront of research interests today due to their potential applications in information technology. A distinct class of skyrmion hosts are rare earth - ... ...

    Abstract Isolated magnetic skyrmions are stable, topologically protected spin textures that are at the forefront of research interests today due to their potential applications in information technology. A distinct class of skyrmion hosts are rare earth - transition metal (RE-TM) ferrimagnetic materials. To date, the nature and the control of basic traits of skyrmions in these materials are not fully understood. We show that for an archetypal ferrimagnetic material that exhibits strong perpendicular anisotropy, the ferrimagnetic skyrmion size can be tuned by external magnetic fields. Moreover, by taking advantage of the high spatial resolution of scanning transmission X-ray microscopy (STXM) and utilizing a large x-ray magnetic linear dichroism (XMLD) contrast that occurs naturally at the RE resonant edges, we resolve the nature of the magnetic domain walls of ferrimagnetic skyrmions. We demonstrate that through this method one can easily discriminate between Bloch and N\'eel type domain walls for each individual skyrmion. For all isolated ferrimagnetic skyrmions, we observe that the domain walls are of N\'eel-type. This key information is corroborated with results of micromagnetic simulations and allows us to conclude on the nature of the Dzyaloshinskii-Moriya interaction (DMI) which concurs to the stabilisation of skyrmions in ferrimagnetic systems. Establishing that an intrinsic DMI occurs in RE-TM materials will also be beneficial towards a deeper understanding of chiral spin texture control in ferrimagnetic materials.
    Keywords Condensed Matter - Materials Science
    Subject code 535
    Publishing date 2023-04-26
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article ; Online: Electrical Detection and Nucleation of a Magnetic Skyrmion in a Magnetic Tunnel Junction Observed via

    Urrestarazu Larrañaga, Joseba / Sisodia, Naveen / Guedas, Rodrigo / Pham, Van Tuong / Di Manici, Ilaria / Masseboeuf, Aurélien / Garello, Kevin / Disdier, Florian / Fernandez, Bruno / Wintz, Sebastian / Weigand, Markus / Belmeguenai, Mohamed / Pizzini, Stefania / Sousa, Ricardo C / Buda-Prejbeanu, Liliana D / Gaudin, Gilles / Boulle, Olivier

    Nano letters

    2024  Volume 24, Issue 12, Page(s) 3557–3565

    Abstract: Magnetic skyrmions are topological spin textures which are envisioned as nanometer scale information carriers in magnetic memory and logic devices. The recent demonstrations of room temperature skyrmions and their current induced manipulation in ... ...

    Abstract Magnetic skyrmions are topological spin textures which are envisioned as nanometer scale information carriers in magnetic memory and logic devices. The recent demonstrations of room temperature skyrmions and their current induced manipulation in ultrathin films were first steps toward the realization of such devices. However, important challenges remain regarding the electrical detection and the low-power nucleation of skyrmions, which are required for the read and write operations. Here, we demonstrate, using
    Language English
    Publishing date 2024-03-18
    Publishing country United States
    Document type Journal Article
    ISSN 1530-6992
    ISSN (online) 1530-6992
    DOI 10.1021/acs.nanolett.4c00316
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Direct Observation of Propagating Spin Waves in the 2D van der Waals Ferromagnet Fe

    Schulz, Frank / Litzius, Kai / Powalla, Lukas / Birch, Max T / Gallardo, Rodolfo A / Satheesh, Sayooj / Weigand, Markus / Scholz, Tanja / Lotsch, Bettina V / Schütz, Gisela / Burghard, Marko / Wintz, Sebastian

    Nano letters

    2023  Volume 23, Issue 22, Page(s) 10126–10131

    Abstract: Magnetism in reduced dimensionalities is of great fundamental interest while also providing perspectives for applications of materials with novel functionalities. In particular, spin dynamics in two dimensions (2D) have become a focus of recent research. ...

    Abstract Magnetism in reduced dimensionalities is of great fundamental interest while also providing perspectives for applications of materials with novel functionalities. In particular, spin dynamics in two dimensions (2D) have become a focus of recent research. Here, we report the observation of coherent propagating spin-wave dynamics in a ∼30 nm thick flake of 2D van der Waals ferromagnet Fe
    Language English
    Publishing date 2023-11-13
    Publishing country United States
    Document type Journal Article
    ISSN 1530-6992
    ISSN (online) 1530-6992
    DOI 10.1021/acs.nanolett.3c02212
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Seeding and Emergence of Composite Skyrmions in a van der Waals Magnet.

    Powalla, Lukas / Birch, Max T / Litzius, Kai / Wintz, Sebastian / Yasin, Fehmi S / Turnbull, Luke A / Schulz, Frank / Mayoh, Daniel A / Balakrishnan, Geetha / Weigand, Markus / Yu, Xiuzhen / Kern, Klaus / Schütz, Gisela / Burghard, Marko

    Advanced materials (Deerfield Beach, Fla.)

    2023  Volume 35, Issue 12, Page(s) e2208930

    Abstract: Topological charge plays a significant role in a range of physical systems. In particular, observations of real-space topological objects in magnetic materials have been largely limited to skyrmions - states with a unitary topological charge. Recently, ... ...

    Abstract Topological charge plays a significant role in a range of physical systems. In particular, observations of real-space topological objects in magnetic materials have been largely limited to skyrmions - states with a unitary topological charge. Recently, more exotic states with varying topology, such as antiskyrmions, merons, or bimerons and 3D states such as skyrmion strings, chiral bobbers, and hopfions, have been experimentally reported. Along these lines, the realization of states with higher-order topology has the potential to open new avenues of research in topological magnetism and its spintronic applications. Here, real-space imaging of such spin textures, including skyrmion, skyrmionium, skyrmion bag, and skyrmion sack states, observed in exfoliated flakes of the van der Waals magnet Fe
    Language English
    Publishing date 2023-02-08
    Publishing country Germany
    Document type Journal Article
    ZDB-ID 1474949-X
    ISSN 1521-4095 ; 0935-9648
    ISSN (online) 1521-4095
    ISSN 0935-9648
    DOI 10.1002/adma.202208930
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article ; Online: Single Skyrmion Generation via a Vertical Nanocontact in a 2D Magnet-Based Heterostructure.

    Powalla, Lukas / Birch, Max T / Litzius, Kai / Wintz, Sebastian / Schulz, Frank / Weigand, Markus / Scholz, Tanja / Lotsch, Bettina V / Kern, Klaus / Schütz, Gisela / Burghard, Marko

    Nano letters

    2022  Volume 22, Issue 23, Page(s) 9236–9243

    Abstract: Skyrmions have been well studied in chiral magnets and magnetic thin films due to their potential application in practical devices. Recently, monochiral skyrmions have been observed in two-dimensional van der Waals magnets. Their atomically flat surfaces ...

    Abstract Skyrmions have been well studied in chiral magnets and magnetic thin films due to their potential application in practical devices. Recently, monochiral skyrmions have been observed in two-dimensional van der Waals magnets. Their atomically flat surfaces and capability to be stacked into heterostructures offer new prospects for skyrmion applications. However, the controlled local nucleation of skyrmions within these materials has yet to be realized. Here, we utilize real-space X-ray microscopy to investigate a heterostructure composed of the 2D ferromagnet Fe
    Language English
    Publishing date 2022-11-18
    Publishing country United States
    Document type Journal Article
    ISSN 1530-6992
    ISSN (online) 1530-6992
    DOI 10.1021/acs.nanolett.2c01944
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article ; Online: Deterministic Field-Free Skyrmion Nucleation at a Nanoengineered Injector Device.

    Finizio, Simone / Zeissler, Katharina / Wintz, Sebastian / Mayr, Sina / Weßels, Teresa / Huxtable, Alexandra J / Burnell, Gavin / Marrows, Christopher H / Raabe, Jörg

    Nano letters

    2019  Volume 19, Issue 10, Page(s) 7246–7255

    Abstract: Magnetic skyrmions are topological solitons promising for applications as encoders for digital information. A number of different skyrmion-based memory devices have been recently proposed. In order to demonstrate a viable skyrmion-based memory device, it ...

    Abstract Magnetic skyrmions are topological solitons promising for applications as encoders for digital information. A number of different skyrmion-based memory devices have been recently proposed. In order to demonstrate a viable skyrmion-based memory device, it is necessary to reliably and reproducibly nucleate, displace, detect, and delete the magnetic skyrmions, possibly in the absence of external applied magnetic fields, which would needlessly complicate the device design. While the skyrmion displacement and detection have both been thoroughly investigated, much less attention has been dedicated to the study of the skyrmion nucleation process and its sub-nanosecond dynamics. In this study, we investigate the nucleation of magnetic skyrmions from a dedicated nanoengineered injector, demonstrating the reliable magnetic skyrmion nucleation at the remnant state. The sub-nanosecond dynamics of the skyrmion nucleation process were also investigated, allowing us to shine light on the physical processes driving the nucleation.
    Language English
    Publishing date 2019-09-20
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ISSN 1530-6992
    ISSN (online) 1530-6992
    DOI 10.1021/acs.nanolett.9b02840
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Article ; Online: Spin-Wave Emission from Vortex Cores under Static Magnetic Bias Fields.

    Mayr, Sina / Flajšman, Lukáš / Finizio, Simone / Hrabec, Aleš / Weigand, Markus / Förster, Johannes / Stoll, Hermann / Heyderman, Laura J / Urbánek, Michal / Wintz, Sebastian / Raabe, Jörg

    Nano letters

    2021  Volume 21, Issue 4, Page(s) 1584–1590

    Abstract: We studied the influence of a static in-plane magnetic field on the alternating-field-driven emission of nanoscale spin waves from magnetic vortex cores. Time-resolved scanning transmission X-ray microscopy was used to image spin waves in disk structures ...

    Abstract We studied the influence of a static in-plane magnetic field on the alternating-field-driven emission of nanoscale spin waves from magnetic vortex cores. Time-resolved scanning transmission X-ray microscopy was used to image spin waves in disk structures of synthetic ferrimagnets and single ferromagnetic layers. For both systems, it was found that an increasing magnetic bias field continuously displaces the wave-emitting vortex core from the center of the disk toward its edge without noticeably altering the spin-wave dispersion relation. In the case of the single-layer disk, an anisotropic lateral expansion of the core occurs at higher magnetic fields, which leads to a directional rather than radial-isotropic emission and propagation of waves. Micromagnetic simulations confirm these findings and further show that focusing effects occur in such systems, depending on the shape of the core and controlled by the static magnetic bias field.
    Language English
    Publishing date 2021-02-05
    Publishing country United States
    Document type Journal Article
    ISSN 1530-6992
    ISSN (online) 1530-6992
    DOI 10.1021/acs.nanolett.0c03740
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  10. Book ; Online: Tailoring Optical Excitation to Control Magnetic Skyrmion Nucleation

    Kern, Lisa-Marie / Pfau, Bastian / Schneider, Michael / Gerlinger, Kathinka / Deinhart, Victor / Wittrock, Steffen / Sidiropoulos, Themistoklis / Engel, Dieter / Will, Ingo / Günther, Christian M. / Litzius, Kai / Wintz, Sebastian / Weigand, Markus / Büttner, Felix / Eisebitt, Stefan

    2022  

    Abstract: In ferromagnetic multilayers, a single laser pulse with a fluence above an optical nucleation threshold can create magnetic skyrmions, which are randomly distributed over the area of the laser spot. However, in order to study the dynamics of skyrmions ... ...

    Abstract In ferromagnetic multilayers, a single laser pulse with a fluence above an optical nucleation threshold can create magnetic skyrmions, which are randomly distributed over the area of the laser spot. However, in order to study the dynamics of skyrmions and for their application in future data technology, a controllable localization of the skyrmion nucleation sites is crucial. Here, it is demonstrated that patterned reflective masks behind a thin magnetic film can be designed to locally tailor the optical excitation amplitudes reached, leading to spatially controlled skyrmion nucleation on the nanometer scale. Using x-ray microscopy, the influence of nanopatterned back-side aluminum masks on the optical excitation is studied in two sample geometries with varying layer sequence of substrate and magnetic Co/Pt multilayer. Surprisingly, the masks' effect on suppressing or enhancing skymion nucleation reverses when changing this sequence. Moreover, optical near-field enhancements additionally affect the spatial arrangement of the nucleated skyrmions. Simulations of the spatial modulation of the laser excitation, and the following heat transfer across the interfaces in the two sample geometries are employed to explain these observations. The results demonstrate a reliable approach to add nanometer-scale spatial control to optically induced magnetization processes on ultrafast timescales.
    Keywords Condensed Matter - Materials Science ; Condensed Matter - Mesoscale and Nanoscale Physics
    Subject code 530
    Publishing date 2022-05-26
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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