Single-shot time-resolved magnetic x-ray absorption at a free-electron laser

Jal, Emmanuelle; Makita, Mikako; Rösner, Benedikt; Dávid, Christian; Nolting, F.; Raabe, Jörg; Savchenko, Tatiana; Kleibert, Armin; Capotondi, Flavio; Pedersoli, Emanuele; Raimondi, Lorenzo; Manfredda, Michele; Nikolov, Ivaylo; Li, Xuan; Merhe, Alaa El Dine; Jaouen, N.; Gorchon, Jon; Malinowski, Grégory; Hehn, Michel; Vodungbo, Boris; Lüning, J.

doi:10.1103/physrevb.99.144305

Cited by 15 publications

(27 citation statements)

References 49 publications

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“…Surprisingly, from a quantitative perspective, our results show rather poor agreement with the literature data. At the Co edge, we obtain τ M (Co) = 110 ± 30 fs (with almost no impact of the employed pump fluence, as shown in Table I), which is slightly smaller than what has been reported so far for pure Co thin films [5], as well as for ferro- [24,39] and ferrimagnetic [25,40,41] Co-based alloys. At the Tb edge, where our fits yield τ M (Tb) = 220 ± 30 fs, the discrepancy is even more pronounced.…”

Section: B Ultrafast Demagnetizationmentioning

confidence: 51%

Laser-induced ultrafast demagnetization and perpendicular magnetic anisotropy reduction in a Co88Tb12 thin film with stripe domains

et al. 2020

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We use time-resolved x-ray resonant magnetic scattering (TR-XRMS) at the Co M 2,3 and Tb O 1 edges to study ultrafast demagnetization in an amorphous Co 88 Tb 12 alloy with stripe domains. Combining the femtosecond temporal with nanometer spatial resolution of our experiment, we demonstrate that the equilibrium spin texture of the thin film remains unaltered by the optical pump pulse on ultrashort timescales (<1 ps). However, after 4 ps, we observe the onset of a significant domain wall broadening, which we attribute to a reduction of the uniaxial magnetic anisotropy of the system, due to energy transfer to the lattice. Static temperature-dependent magnetometry measurements combined with analytical modeling of the magnetic structure of the thin film corroborate this interpretation.

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Section: B Ultrafast Demagnetizationmentioning

confidence: 51%

Laser-induced ultrafast demagnetization and perpendicular magnetic anisotropy reduction in a Co88Tb12 thin film with stripe domains

et al. 2020

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“… 8,9 In this way, it is not only possible to conduct an entire pump-probe experiment in a single snapshot, but also to design parts of the zone plate for discrete energies in a fixed geometry, and thus to maintain a uniform timescale across the dynamics of multiple elements. While the very good, jitter-free temporal resolution is an inherent advantage of the streaking approach, 9 the absolute temporal comparison of the starting dynamics for both Fe and Ni elements is only possible when using a two-color pulse to probe the system. This is the motivation for the development of the two-color schemes described in this paper.…”

Section: Discussionmentioning

confidence: 99%

Simultaneous two-color snapshot view on ultrafast charge and spin dynamics in a Fe-Cu-Ni tri-layer

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et al. 2020

Structural Dynamics

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Ultrafast phenomena on a femtosecond timescale are commonly examined by pump-probe experiments. This implies multiple measurements, where the sample under investigation is pumped with a short light pulse and then probed with a second pulse at various time delays to follow its dynamics. Recently, the principle of streaking extreme ultraviolet (XUV) pulses in the temporal domain has enabled recording the dynamics of a system within a single pulse. However, separate pump-probe experiments at different absorption edges still lack a unified timing, when comparing the dynamics in complex systems. Here, we report on an experiment using a dedicated optical element and the two-color emission of the FERMI XUV free-electron laser to follow the charge and spin dynamics in composite materials at two distinct absorption edges, simultaneously. The sample, consisting of ferromagnetic Fe and Ni layers, separated by a Cu layer, is pumped by an infrared laser and probed by a two-color XUV pulse with photon energies tuned to the M-shell resonances of these two transition metals. The experimental geometry intrinsically avoids any timing uncertainty between the two elements and unambiguously reveals an approximately 100 fs delay of the magnetic response with respect to the electronic excitation for both Fe and Ni. This delay shows that the electronic and spin degrees of freedom are decoupled during the demagnetization process. We furthermore observe that the electronic dynamics of Ni and Fe show pronounced differences when probed at their resonance, while the demagnetization dynamics are similar. These observations underline the importance of simultaneous investigation of the temporal response of both charge and spin in multi-component materials. In a more general scenario, the experimental approach can be extended to continuous energy ranges, promising the development of jitter-free transient absorption spectroscopy in the XUV and soft X-ray regimes.

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“…Indeed, performing pure absorption measurements at X-ray free electron lasers (FELs) has been challenging, due to intrinsic fluctuations of the photon parameters and the lack of a reliable and linear incident intensity monitor [25]. However, motivated by time-resolved absorption experiments performed at femtoslicing facilities [17,22], as well as time-and spin-resolved photoelectron spectroscopy at high harmonic generation (HHG) sources [26,27], new technical advances were recently made to probe X-ray absorption dynamics using FEL [25,[28][29][30][31] and HHG [32,33], thereby laying the ground for a systematic analysis of charge and spin dynamics [30,34].…”

Section: Introductionmentioning

confidence: 99%

Time-Resolved XUV Absorption Spectroscopy and Magnetic Circular Dichroism at the Ni M2,3-Edges

et al. 2020

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Ultrashort optical pulses can trigger a variety of non-equilibrium processes in magnetic thin films affecting electrons and spins on femtosecond timescales. In order to probe the charge and magnetic degrees of freedom simultaneously, we developed an X-ray streaking technique that has the advantage of providing a jitter-free picture of absorption cross-section changes. In this paper, we present an experiment based on this approach, which we performed using five photon probing energies at the Ni M2,3-edges. This allowed us to retrieve the absorption and magnetic circular dichroism time traces, yielding detailed information on transient modifications of electron and spin populations close to the Fermi level. Our findings suggest that the observed absorption and magnetic circular dichroism dynamics both depend on the extreme ultraviolet (XUV) probing wavelength, and can be described, at least qualitatively, by assuming ultrafast energy shifts of the electronic and magnetic elemental absorption resonances, as reported in recent work. However, our analysis also hints at more complex changes, highlighting the need for further experimental and theoretical studies in order to gain a thorough understanding of the interplay of electronic and spin degrees of freedom in optically excited magnetic thin films.

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Single-shot time-resolved magnetic x-ray absorption at a free-electron laser

Cited by 15 publications

References 49 publications

Laser-induced ultrafast demagnetization and perpendicular magnetic anisotropy reduction in a Co88Tb12 thin film with stripe domains

Laser-induced ultrafast demagnetization and perpendicular magnetic anisotropy reduction in a Co88Tb12 thin film with stripe domains

Simultaneous two-color snapshot view on ultrafast charge and spin dynamics in a Fe-Cu-Ni tri-layer

Time-Resolved XUV Absorption Spectroscopy and Magnetic Circular Dichroism at the Ni M2,3-Edges

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