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Current-induced domain wall oscillations in a nanowire imaged by time-resolved photoemission electron microscopy
摘要： We study reversible domain wall motion in half-ring Ni80Fe20 nanowires on a nanosecond (ns) timescale in a truly current-induced pump-probe experiment using an energy filtered, aberration-corrected photoemission electron microscope. The x-ray magnetic circular dichroism signal is probed at different time delays before, during and after the current pulse in a stroboscopic mode with circularly polarized synchrotron radiation in the energy range of the Fe L3-edge (707 eV). We observe lateral domain wall oscillations with a frequency of ～ 0.4 GHz. Comparing the results to a proposed string model, we find that the domain wall oscillations can be described as string-like asymmetric oscillations.
关键词： Synchrotron radiation,Photoemission electron microscopy,X-ray magnetic circular dichroism,Pump-probe mode
更新于2025-09-23 15:23:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Petahertz Magnetization Dynamics
摘要： In contrast to conventional electronics, where only the charge of electrons is considered, spintronics is based on the utilization of both charge and spin. Due to this additional degree of freedom, spintronic devices can potentially provide higher processing speed or better energy efficiency. However, while sub-femtosecond control of the electronic properties of solids has previously been demonstrated, the lack of direct coupling between light and spin has limited the manipulation speed of magnetic properties to the few-tens-of-femtoseconds timescale. Here we introduce a technique able to follow the magnetic properties of a solid with attosecond resolution and demonstrate the direct sub-femtosecond all-optical manipulation of its spin degrees of freedom. We probe the time-evolution of the magnetic and electronic properties of solids and their coupling using a novel atto-XMCD scheme. In our experiment, a circularly polarized attosecond pulse (probe) (~310 as FWHM duration, centered at 66 eV corresponding to the M-edges of Nickel) is transmitted through a thin magnetized Nickel (Ni) film or Nickel-Platinum (Ni/Pt) multilayer sample. Reversing the magnetization direction allows to record the polarization dependent X-Ray absorption of Ni (X-Ray Magnetic Circular Dichroism, XMCD), which directly measures the magnetic moment of the Ni atoms. Dynamics are initiated by a carrier-envelope-phase stable sub-4 fs near-infrared electric laser field (pump). Coincidentally, attosecond transient absorption spectroscopy reveals changes of the electronic properties and gives a clear reference for the arrival of the laser pulse. Our results show an instantaneous response of both, charge and spin, to the laser pulse electric field in the Ni/Pt multilayer sample (Fig.1 a). The exceptionally fast demagnetization in the first 10 fs after laser excitation is the first experimental evidence for theoretically predicted optically induced spin transfer (OISTR): simultaneously with the charge transfer due to electronic excitation, the spin of excited electrons is transferred from the ferromagnetic (Ni) to the paramagnetic (Pt) material in the multilayer sample. This reduces the majority spin in Ni, inducing an instantaneous demagnetization of the ferromagnet. Fig. 1 b shows a reference measurement performed with a Ni film. As OISTR is not possible in pure Ni, no demagnetization happens during the pump laser pulse. To conclude, with our novel experimental scheme we demonstrate sub-femtosecond optical spin manipulation in matter. Access and control of the magnetic properties of solids on the attosecond time-scale paves the way towards spintronic devices operating at Petahertz clock rates.
关键词： Petahertz clock rates,X-Ray Magnetic Circular Dichroism,optically induced spin transfer,attosecond resolution,spintronics
更新于2025-09-11 14:15:04
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Atomic scale evidence of the switching mechanism in a photomagnetic CoFe dinuclear Prussian Blue Analogue
摘要： Molecular complexes based on Prussian Blue Analogues have recently attracted considerable interest for their unique bistable properties combined to ultimately reduced dimensions. Here, we investigate the first dinuclear FeCo complex exhibiting both thermal and photomagnetic bistability in solid state. Through an experimental and theoretical approach combining local techniques - X-ray Absorption Spectroscopy (XAS), X-ray Magnetic Circular Dichroism (XMCD) and Ligand Field Multiplet calculations, we were able to evidence the changes occuring at the atomic scale in the electronic and magnetic properties. The spectroscopic studies were able to fully support at the atomic level the following conclusions: (i) the 300 K phase and the light-induced excited state at 4 K are both built from FeIII LS—CoII HS paramagnetic pairs with no apparent reorganization of the local structure, (ii) the 100 K phase is composed of FeII LS—CoIII LS diamagnetic pairs, and (iii) the light-induced excited state is fully relaxed at an average temperature of ≈ 50 K. In the paramagnetic phase at 2 K, XAS and XMCD reveal that, both Fe and Co ions exhibit a rather large orbital magnetic moment (0.65 μB and 0.46 μB, respectively under an external magnetic induction of 6.5 T) but it was not possible to detect a magnetic interaction between spin centers above 2 K.
关键词： Ligand Field Multiplet calculations,X-ray Absorption Spectroscopy,X-ray Magnetic Circular Dichroism,photomagnetic bistability,Prussian Blue Analogues
更新于2025-09-10 09:29:36