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Publisher: [London] : Nature Publishing Group UK × Subject: acceleration ×

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Now showing 1 - 4 of 4
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    Self-assembly of Co/Pt stripes with current-induced domain wall motion towards 3D racetrack devices
    ([London] : Nature Publishing Group UK, 2024) Fedorov, Pavel; Soldatov, Ivan; Neu, Volker; Schäfer, Rudolf; Schmidt, Oliver G.; Karnaushenko, Daniil
    Modification of the magnetic properties under the induced strain and curvature is a promising avenue to build three-dimensional magnetic devices, based on the domain wall motion. So far, most of the studies with 3D magnetic structures were performed in the helixes and nanowires, mainly with stationary domain walls. In this study, we demonstrate the impact of 3D geometry, strain and curvature on the current-induced domain wall motion and spin-orbital torque efficiency in the heterostructure, realized via a self-assembly rolling technique on a polymeric platform. We introduce a complete 3D memory unit with write, read and store functionality, all based on the field-free domain wall motion. Additionally, we conducted a comparative analysis between 2D and 3D structures, particularly addressing the influence of heat during the electric current pulse sequences. Finally, we demonstrated a remarkable increase of 30% in spin-torque efficiency in 3D configuration.
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    Disparate ultrafast dynamics of itinerant and localized magnetic moments in gadolinium metal
    ([London] : Nature Publishing Group UK, 2015) Frietsch, B.; Bowlan, J.; Carley, R.; Teichmann, M.; Wienholdt, S.; Hinzke, D.; Nowak, U.; Carva, K.; Oppeneer, P. M.; Weinelt, M.
    The Heisenberg–Dirac intra-atomic exchange coupling is responsible for the formation of the atomic spin moment and thus the strongest interaction in magnetism. Therefore, it is generally assumed that intra-atomic exchange leads to a quasi-instantaneous aligning process in the magnetic moment dynamics of spins in separate, on-site atomic orbitals. Following ultrashort optical excitation of gadolinium metal, we concurrently record in photoemission the 4f magnetic linear dichroism and 5d exchange splitting. Their dynamics differ by one order of magnitude, with decay constants of 14 versus 0.8 ps, respectively. Spin dynamics simulations based on an orbital-resolved Heisenberg Hamiltonian combined with first-principles calculations explain the particular dynamics of 5d and 4f spin moments well, and corroborate that the 5d exchange splitting traces closely the 5d spin-moment dynamics. Thus gadolinium shows disparate dynamics of the localized 4f and the itinerant 5d spin moments, demonstrating a breakdown of their intra-atomic exchange alignment on a picosecond timescale.
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    Retrieving spin textures on curved magnetic thin films with full-field soft X-ray microscopies
    ([London] : Nature Publishing Group UK, 2015) Streubel, Robert; Kronast, Florian; Fischer, Peter; Parkinson, Dula; Schmidt, Oliver G.; Makarov, Denys
    X-ray tomography is a well-established technique to characterize 3D structures in material sciences and biology; its magnetic analogue--magnetic X-ray tomography--is yet to be developed. Here we demonstrate the visualization and reconstruction of magnetic domain structures in a 3D curved magnetic thin films with tubular shape by means of full-field soft X-ray microscopies. The 3D arrangement of the magnetization is retrieved from a set of 2D projections by analysing the evolution of the magnetic contrast with varying projection angle. Using reconstruction algorithms to analyse the angular evolution of 2D projections provides quantitative information about domain patterns and magnetic coupling phenomena between windings of azimuthally and radially magnetized tubular objects. The present approach represents a first milestone towards visualizing magnetization textures of 3D curved thin films with virtually arbitrary shape.
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    Nanoplasmonic electron acceleration by attosecond-controlled forward rescattering in silver clusters
    ([London] : Nature Publishing Group UK, 2017) Passig, Johannes; Zherebtsov, Sergey; Irsig, Robert; Arbeiter, Mathias; Peltz, Christian; Göde, Sebastian; Skruszewicz, Slawomir; Meiwes-Broer, Karl-Heinz; Tiggesbäumker, Josef; Kling, Matthias F.; Fennel, Thomas
    In the strong-field photoemission from atoms, molecules, and surfaces, the fastest electrons emerge from tunneling and subsequent field-driven recollision, followed by elastic backscattering. This rescattering picture is central to attosecond science and enables control of the electron's trajectory via the sub-cycle evolution of the laser electric field. Here we reveal a so far unexplored route for waveform-controlled electron acceleration emerging from forward rescattering in resonant plasmonic systems. We studied plasmon-enhanced photoemission from silver clusters and found that the directional acceleration can be controlled up to high kinetic energy with the relative phase of a two-color laser field. Our analysis reveals that the cluster's plasmonic near-field establishes a sub-cycle directional gate that enables the selective acceleration. The identified generic mechanism offers robust attosecond control of the electron acceleration at plasmonic nanostructures, opening perspectives for laser-based sources of attosecond electron pulses.