Understanding the ultrafast demagnetization of transition metals requires pump-probe experi ments sensitive to the time evolution of the electronic, spin and lattice thermodynamic baths. By means of time-resolved photoelectron energy and spin polarization measurements in the low pump f luence regime on iron, we disentangle the different dynamics of hot electrons and demagnetization in the sub-ps and ps time range. We observe a broadening of the Fermi-Dirac distribution, following the excitation of non-thermal electrons at specific region of the iron valence band. The corresponding reduction of the spin polarization is remarkably delayed with respect to the dynamic of electronic temperature. The experimental results are corroborated with a microscopic 3-temperature model highlighting the role of thermal disorder in the quenching of the average spin magnetic moment, indicating Elliot-Yafet type spin-flip scattering as the main mediation mechanism, with a spin-flip probability of 0.1 and a rate of energy exchange between electrons and lattice of 2.5 Kfs−1.
Relevance of thermal disorder in the electronic and spin ultrafast dynamics of iron in the low-perturbation regime
Pierantozzi, G. M.;De Vita, A.;Cucini, R.;Finardi, A. M.;Pincelli, T.;Fujii, J.;Dri, C.;Panaccione, G.;Rossi, G.
2024
Abstract
Understanding the ultrafast demagnetization of transition metals requires pump-probe experi ments sensitive to the time evolution of the electronic, spin and lattice thermodynamic baths. By means of time-resolved photoelectron energy and spin polarization measurements in the low pump f luence regime on iron, we disentangle the different dynamics of hot electrons and demagnetization in the sub-ps and ps time range. We observe a broadening of the Fermi-Dirac distribution, following the excitation of non-thermal electrons at specific region of the iron valence band. The corresponding reduction of the spin polarization is remarkably delayed with respect to the dynamic of electronic temperature. The experimental results are corroborated with a microscopic 3-temperature model highlighting the role of thermal disorder in the quenching of the average spin magnetic moment, indicating Elliot-Yafet type spin-flip scattering as the main mediation mechanism, with a spin-flip probability of 0.1 and a rate of energy exchange between electrons and lattice of 2.5 Kfs−1.File | Dimensione | Formato | |
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