Séminaire LCPMR | Nanna Zhou Hagström "Symmetry-dependent ultrafast manipulation of nanoscale magnetic domains
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Le 20 avr. 2023
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10:00 - 11:30
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Séminaire
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Sorbonne-Université, Campus Pierre et Marie Curie
UFR de Chimie, tour 32-42, salle 101
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Emmanuelle Jal
| SÉMINAIRE | PERSONNALITÉ INVITÉE |
| Titre |
SYMMETRY-DEPENDENT ULTRAFAST MANIPULATION OF NANOSCALE MAGNETIC DOMAINS |
| Présentée par | |
| Affectation | Department of Material Science and Engineering, University of California Davis, Davis, California |
| Résumé | The quest towards controlling magnetism at the femtosecond timescales is driven by the demand for energy efficient and fast magnetic storage devices [1]. Many studies have focused on switching the magnetization in different material, but few have discussed the role of the spatial evolution of the magnetization. Here, we study the ultrafast response of magnetic multilayers with domain patterns with different local symmetries [2]. Through time-resolved small angle X-ray scattering at the European XFEL and an accurate 2D fitting routing, we find a symmetry-dependent behavior of the ultrafast response. By observing an ultrafast shift in the scattering peak position for labyrinth domains, without translational symmetry, but no such shift stripe domains, with translational symmetry, we confirm the results of previous studies [3]. We also study regions of the sample where both labyrinth and stripe characters are present. By isolating the isotropic and anisotropic components of the scattering, we find that only the labyrinth domains exhibit an ultrafast shift in the isotropic diffraction peak position, even in a mixed domain pattern. In a subsequent experiment at the FERMI free electron laser, we found that the ultrafast distortion of the diffraction pattern showed markedly different timescales compared to the magnetization quenching [4]. The diffraction pattern distortion shows a threshold-dependence with laser fluence, not seen for magnetization quenching, consistent with a picture of domain wall motion with pinning sites. Supported by simulations, we show that a speed of ≈ 66 km/s for highly curved domain walls can explain the experimental data. While our data agree with the prediction of extreme, nonequilibrium wall speeds locally, it differs from the details of the theory, suggesting that additional mechanisms are required to fully understand these effects. [1] A. Kirilyuk, A. V. Kimel, and Th. Rasing, Rev. Mod. Phys. 82, 2731-2784 (2010) [2] N. Zhou Hagström et al., Phys. Rev. B 106, 224424 (2022) [3] B. Pfau et al., Nature Communications 3, 1110 (2012); D. Zusin et al, Phys. Rev. B 106, 144422 (2022); M. Hennes et al., Phys. Rev. B 102, 174437 (2020) [4] R. Jangid, https://arxiv.org/abs/2303.16131 |
| Contact LCPMR | Emmanuelle JAL |