State-resolved ultrafast charge and spin dynamics in [Co/Pd] multilayers

We use transient absorption spectroscopy with circularly polarized x rays to detect laser-excited hole states below the Fermi level and compare their dynamics with that of unoccupied states above the Fermi level in ferromagnetic [Co/Pd] multilayers. While below the Fermi level, an instantaneous and significantly stronger demagnetization is observed, above the Fermi level, the demagnetization is delayed by 35 +/- 10 fs. This provides a direct visualization of how ultrafast demagnetization proceeds via initial spin-flip scattering of laser-excited holes to the subsequent formation of spin waves. (C)& nbsp;2022 Author(s).

Automated summary

Using transient absorption spectroscopy with circularly polarized x rays, we investigated the dynamics of laser-excited hole states below the Fermi level and unoccupied states above the Fermi level in ferromagnetic [Co/Pd] multilayers. The results show an instantaneous and significantly stronger demagnetization below the Fermi level, while the demagnetization above the Fermi level is delayed by 35 +/- 10 fs. This provides a direct visualization of the process of ultrafast demagnetization involving spin-flip scattering of laser-excited holes and subsequent formation of spin waves.