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Element-Selective Probing of Ultrafast Ferromagnetic-Antiferromagnetic Order Dynamics in Fe/CoO Bilayers

Chowdhury S. Awsaf1, Sangeeta Thakur1, Markus Weißenhofer1,2, Jendrik Gördes1, Marcel Walter1, Mohamad-Assaad Mawass3,*, Niko Pontius3, Christian Schüßler-Langeheine3, Peter M. Oppeneer2 et al.

Wolfgang Kuch1,†

  • *Present address: Department of Mathematics and Physics, American University of Ras Al Khaimah, Ras Al Khaimah, United Arab Emirates.
  • †Contact author: kuch@physik.fu-berlin.de
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Phys. Rev. Lett. 136, 126705 – Published 27 March, 2026

DOI: https://doi.org/10.1103/gcwk-tsj5

Abstract

The ultrafast magnetization dynamics of an epitaxial Fe/CoO bilayer on Ag(001) is examined in an element-resolved way by resonant soft-x-ray reflectivity. The transient magnetic linear dichroism at the Co L2 edge and the magnetic circular dichroism at the Fe L3 edge measured in reflection in a pump–probe experiment with 120 fs temporal resolution show the loss of antiferromagnetic and ferromagnetic order in CoO and Fe, respectively, both within 300 fs after excitation with 60 fs light pulses of 800 and 400 nm wavelengths. A comparison to spin-dynamics simulations using an atomistic spin model shows that direct energy transfer from the laser-excited electrons in Fe to the magnetic moments in CoO provides the dominant demagnetization channel in the case of 800-nm excitation.

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Phys. Rev. Lett. 136, 126705– Published 27 March, 2026
  • Received 26 August 2024
  • Revised 24 November 2025
  • Accepted 25 February 2026
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