Using the photoinduced <i>L</i>3 resonance shift in Fe and Ni as time reference for ultrafast experiments at low flux soft x-ray sources

Jana, Somnath; Muralidhar, Shreyas; Åkerman, Johan; Schüßler-Langeheine, Christian; Pontius, N.

doi:10.1063/4.0000108

Cited by 2 publications

(1 citation statement)

References 44 publications

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“…To determine time zero of the pump-probe experiment for the recorded transient X-ray spectra with highest possible precision, a MoSi multi-layer reference sample was used 48,49 . To correct for slow drifts of time-zero we employed the following measurement procedure: Time zero was determined on the MoSi multi-layer by repeated delay scans with a net acquisition time of 1 hour.…”

Section: Experimental Methodsmentioning

confidence: 99%

Mapping the energy-time landscape of spins with helical X-rays

Pontius¹,

Dewhurst²,

Schüßler-Langeheine³

et al. 2022

Preprint

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Unveiling the key mechanisms that determine optically driven spin dynamics is essential both to probe the fundamental nature of ultrafast light-matter interactions, but also to drive future technologies of smaller, faster, and more energy efficient devices. Essential to this task is the ability to use experimental spectroscopic tools to evidence the underlying energy-and spin-resolved dynamics of non-equilibrium electron occupations. In this joint theory and experimental work, we demonstrate that ultrafast helicity-dependent soft X-ray absorption spectroscopy (HXAS) allows access to spin-, time-and energy specific state occupation after optical excitation. We apply this method to the prototype transition metal ferromagnet cobalt and find convincing agreement between theory and experiment. The richly structured energy-resolved spin dynamics unveil the subtle interplay and characteristic time scales of optical excitation and spin-orbit induced spin-flip transitions in this material: the spin moment integrated in an energy window below the Fermi level first exhibits an ultrafast increase as minority carriers are excited by the laser pulse, before it is reduced as spin-flip process in highly localized, low energy states start to dominate. The results of this study demonstrate the power of element specific transient HXAS, placing it as a potential new tool for identifying and determining the role of fundamental processes in optically driven spin dynamics in magnetic materials.

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Section: Experimental Methodsmentioning

confidence: 99%

Mapping the energy-time landscape of spins with helical X-rays

Pontius¹,

Dewhurst²,

Schüßler-Langeheine³

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

Experimental confirmation of the delayed Ni demagnetization in FeNi alloy

Jana

Knut

Muralidhar

et al. 2022

Applied Physics Letters

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Element-selective techniques are central for the understanding of ultrafast spin dynamics in multi-element materials, such as magnetic alloys. Recently, however, it turned out that the commonly used technique of the transverse magneto-optical Kerr effect (T-MOKE) in the extreme ultraviolet range may have issues with unwanted crosstalk between different elemental signals and energy-dependent non-linear response. This problem can be sizeable, which puts recent observations of ultrafast spin transfer from Fe to Ni sites in FeNi alloys into question. In this study, we investigate the Fe-to-Ni spin transfer in a crosstalk-free time-resolved x-ray magnetic circular dichroism (XMCD) experiment with a reliable time reference. With XMCD near the absorption maxima, we find a very similar Fe and Ni dynamics as with T-MOKE from identical samples. Considering the potential non-linearities of the T-MOKE response, such a good agreement in our findings is remarkable. Our data provide the ongoing discussion about ultrafast spin-transfer mechanisms in FeNi systems with a broader experimental basis.

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Using the photoinduced L3 resonance shift in Fe and Ni as time reference for ultrafast experiments at low flux soft x-ray sources

Cited by 2 publications

References 44 publications

Mapping the energy-time landscape of spins with helical X-rays

Mapping the energy-time landscape of spins with helical X-rays

Experimental confirmation of the delayed Ni demagnetization in FeNi alloy

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