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MA: Fachverband Magnetismus

MA 38: Ultrafast Magnetization Effects III

MA 38.1: Talk

Thursday, March 21, 2024, 11:15–11:30, EB 202

Ultrafast changes in the M₅/M₄ branching ratio in Terbium — •Tim Amrhein¹, Beyza Salantur¹, Niko Pontius², Christian Schuessler-Langeheine², Martin Weinelt¹, and Nele Thielemann-Kühn¹ — ¹Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin, Germany — ²Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany

As reported recently, inelastic 5d-4f electronic scattering in 4f rare earth metals transiently alters the 4f orbital state and therewith the total angular momentum J [1]. These transitions change the electronic and magnetic properties in 4f metals on ultrafast time scales. Within an X-ray absorption study performed at the FemtoSpeX slicing facility at BESSY II we show, that the observed changes of J also affect the M₅/M₄ branching ratio on ultrafast timescales in Terbium, proving the 3rd rule of Thole and Van der Laan [2] to be applicable in non-equilibrium. The change of the branching ratio can be used, to calculate the percentage of 4f-excited atoms.

[1] N. Thielemann-Kühn et al., Optical control of 4f orbital state in rare-earth metals. https://doi.org/10.48550/arXiv.2106.09999 (Science Advances, in revision)

[2] B. T. Thole and G. van der Laan., Branching ratio in x-ray absorption spectroscopy. Phys. Rev. B, 38:3158-3171, Aug 1988.

Keywords: X-ray absorption; ultrafast; rare earths; inelastic 5d-4f electronic scattering